Applied Mechanics Research and Researchers

We are migrating to iMechanica.Org

2006-09-09T09:24:00.000-07:00

Making Sense of the Web's Structure

2006-09-08T10:52:00.000-07:00

Scientists in Britain report baldness breakthrough

2006-09-03T14:51:00.000-07:00

Should anyone write a Wiki textbook on Mechanics of Materials ?

2006-09-02T10:48:00.000-07:00

Here is an article on Wiki-style textbook in general.

My question is: Can we do something to help students in developing countries get free textbooks on applied mechanics ? Should NSF support such effort ?

Gene therapy breakthrough against skin cancer

2006-09-02T10:40:00.000-07:00

A New Class of Composite Materials - Graphene-based Composite Materials

2006-08-29T17:12:00.000-07:00

Professor Rodney Ruoff and colleagues at Northwestern University and Purdue University have developed a process that promises to lead to the creation of a new class of composite materials - graphene-based materials. They reported the results of their research in Nature, 442 (2006) 282-286. This team has overcome the difficulties of yielding a uniform distribution of graphene-based sheets in a polymer matrix. Such composites can be readily processed using standard industrial technologies such as moulding and hot-pressing. The technique should be applicable to a wide variety of polymers. The graphene composites may compete with carbon nanotube-based materials in terms of mechanical properties. This new class of composites may stimulate the applied mechanics community to study the fundamental reinforcing mechanisms of graphene sheets from both experimental and theoretical approaches.

Tony Evans Elected a Fellow of the Royal Academy of Engineering

2006-08-29T11:44:00.000-07:00

The drama of a mathematical proof

2006-08-26T15:03:00.000-07:00

An article in this week’s New Yorker describes the human drama behind a proof of the Poincare conjecture, one of the seven Millennium Problems. The article is unsparing of several mathematicians of Chinese origin.

Notes added on 27 August.

Perelman turns down Fields Medal.
Here is an excellent article on the proof in the New York Times.
See the comment posted by Ting Zhu.

R.S. Rivlin is awarded the Engineering Science Medal

2006-08-15T07:00:00.000-07:00

Young Huang is awarded the 2006 SES Young Investigator Medal (University of Illinois at Urbana-Champaign)

2006-08-15T06:58:00.000-07:00

Professor Young Huang of University of Illinois at Urbana-Champaign is awarded the 2006 Society of Engineering Science (SES) Young Investigator award for his contributions on strain-gradient plasticity theory, computational nano-mechanics, and computational dislocation dynamics and plasticity.

Alan Needleman is awarded the 2006 Prager Medal (Brown University)

2006-08-15T06:56:00.000-07:00

Professor Alan Needleman of Brown University is awarded the 2006 Prager Medal for his contribution in computational failure mechanics, dislocation dynamics, modeling and simulations of fractures and strain localizations, plasticity theories, and most recently contact and adhesion at small scales.

Meshfree Methods: Its origin, history, and theories

2006-08-12T16:40:00.000-07:00

The following article is written by Dr.-Ing. Timon Rabczuk, who is now teaching finite element methods and meshfree methods at Technical University of Munich, Germany, for a sister blog --- Meshfree Methods Blog.
I enjoyed reading the article very much, and would like to share it with you.

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Meshfree methods go back to the seventies. The major difference to finite element methods is that the domain of interest is discretized only with nodes, often called particles. These particles interact via meshfree shape functions in a continuum framework similar as finite elements do although particle “connectivities” can change over the course of a simulation. This flexibility of meshfree methods was exploited in applications with large deformations in fluid and solid mechanics, e.g. free-surface flow, metal forming, fracture and fragmentation, to name a few. Most meshfree methods are pure Lagrangian in character though there are a few publications on meshfree methods formulated in an Eulerian (or ALE) description, e.g. Fries 2005. The most important advantages of meshfree methods compared to finite elements are: their higher order continuous shape functions that can be exploited e.g. for thin shells or gradient-enhanced constitutive models; higher smoothness; simpler incorporation of h- and p-adaptivity and certain advantages in crack problems (no mesh alignment sensitivity; some methods do not need to enforce crack path continuity). The most important drawback of meshfree methods is probably their higher computational cost, regardless of some instabilities that certain meshfree methods have.

One of the oldest meshfree methods is the Smooth Particle Hydrodynamics (SPH) developed by Lucy and Gingold and Monaghan in 1971. SPH was first applied in astrophysics to model phenomena such as supernova and was later employed in fluid dynamics. In 1993, Petschek and Libersky extended SPH to solid mechanics. Early SPH formulations suffered from spurious instabilites and inconsistencies that were a hot topic of investigations, especially in the 90s. Many corrected SPH versions were developed that improved either the stability behavior of SPH or its consistency. Consistency, often referred to as completeness in a Galerkin framework, means the ability to reproduce exactly a polynomial of certain order. A method is called n-th order consistent (or complete) if it is able to reproduce a polynomial of order n exactly. While most SPH methods are based on the strong form, a wide class of methods was developed based on the weak form.

Based on an idea of Lancaster and Salkauskas and probably motivated by the purpose to model arbitrary crack propagation without computational expensive remeshing, the group of Prof. Ted Belytschko developed the elementfree Galerkin (EFG) method in 1994. The EFG method is based on an MLS approximation and avoids inconsistencies inherent of some SPH formulations. In 1995, the group of Prof. W.K. Liu proposed a similar method, the Reproducing Kernel Particle Method (RKPM). Though the method is very similar to the EFG method, it originates from wavelets rather than from curve-fitting. The first method that employed an extrinsic basis was the hp-cloud method of Duarte and Oden. In contrast to the EFG and RKPM method, the hp-cloud method increases the order of consistency (or completeness) by an extrinsic basis. In other words, additional unknowns were introduced into the variational formulation to increase the order of completeness. This idea was later adopted (and modified) in the XFEM context though the extrinsic basis (or extrinsic enrichment) was used to describe the crack kinematics rather than to increase the order of completeness in a p-refinement sense. The group of Prof. Ivo Babuska discovered certain similarities between finite element and meshfree methods and formulated a general framework, the Partition of Unity Finite Element Method (PUFEM), that is similar to the generalized Finite Element Method (GFEM) of Strouboulis and colleagues. Another very popular meshfree method worth mentioning is the Meshless Local Petrov Galerkin (MLPG) method developed by the group of Prof. S.N. Atluri in 1998. The main difference of the MLPG method to all other methods mentioned above is that local weak forms are generated over overlapping sub-domains rather than using global weak forms. The integration of the weak form is then carried out in these local sub-domains. In this context, Atluri introduced the notion “truly” meshfree methods since truly meshfree methods do not need a construction of a background mesh that is needed for integration.

The issue of integration in meshfree methods was a topic of investigations since its early times. Methods that are based on a global weak form may use three different types of integration schemes: nodal integration, stress-point integration and integration (usually Gauss quadrature) based on a background mesh that does not necessarily need to be aligned with the particles. Nodal integration is from the computational point of view the easiest and cheapest way to build the discrete equations but similar to reduced finite elements, meshfree methods based on nodal integration suffer from an instability due to rank deficiency. Adding stress points to the nodes can eliminate (or at least alleviate) this instability. The term stress-point integration comes from the fact that additional nodes were added to the particles where only stresses are evaluated. All kinematic values are obtained from the "original" particles. The concept of stress points was actually first introduced in one dimension in an SPH setting by Dyka. This concept was introduced into higher order dimensions by Randles and Libersky and the group of Prof. Belytschko. There is a subtle difference between the stress point integration of Belytschko and Randles and Libersky. While Randles and Libersky evaluate stresses only at the stress points, Belytschko and colleagues evaluate stresses also at the nodes. Meanwhile, many different versions of stress point integration were developed. The most accurate way to obtain the governing equations is Gauss quadrature. In contrast to finite elements, integration in meshfree methods is not exact. A background mesh has to be constructed and usually a larger number of quadrature points as in finite elements are used. For example, while usually 4 quadrature points are used in linear quadrilateral finite elements, Belytschko recommend the use of 16 quadrature points in the EFG method.

Another important issue regarding the stability of meshfree methods is related to the kernel function, often called window or weighting function. The kernel function is somehow related to the meshfree shape function (depending on the method). The kernel function can be expressed in terms of material coordinates or spatial coordinates. We then refer to Lagrangian or Eulerian kernels, respectively. Early meshfree methods such as SPH use an Eulerian kernel. Many meshfree methods that are based on Eulerian kernels have a so-called tensile instability, meaning the method gets unstable when tensile stresses occur. In a sequence of papers by Belytschko, it was shown that the tensile instability is caused by the use of an Eulerian kernel. Meshfree methods based on Lagrangian kernels do not show this type of instability. Moreover, it was demonstrated that for some given strain softening constitutive models, methods based on Eulerian kernels were not able to detect the onset of material instability correctly while methods that use Lagrangian kernels were able to detect the onset of material instability correctly. This is a striking drawback of Eulerian kernels when one wishes to model fracture. However, a general stability analysis is difficult to perform and will of course also depend on the underlying constitutive model. Note also, that Libersky proposed a method based on Eulerian kernels and showed stability in the tension region though he did not consider strain softening materials. For too large deformations, methods based on Lagrangian kernels tend to get unstable as well since the domain of influence in the current configuration can become extremely distorted. Some recent methods to model fracture try to combine Lagrangian and Eulerian kernels though certain aspects still have to be studied, e.g. what happens in the transition area or how are additional unknowns treated (in case an enrichment is used).

In meshfree methods, we talk about approximation rather than interpolation since the meshfree shape functions do not satisfy the Kronecker-delta property. This entails certain difficulties in imposing essential boundary conditions. Probably the simplest way to impose essential boundary conditions is by boundary collocations. Another opportunity is to use the penalty method, Lagrange multipliers or Nitsche’s method. Coupling to finite elements is one more alternative that was extensively pursued in the literature-in this case, the essential boundary conditions are imposed in the finite element domain. In the first coupling method by Belytschko, the meshfree nodes have to be located at the finite element nodes and a blending domain is constructed such that the shape functions are zero at the finite element boundary. In this first approach, discontinuous strains were obtained at the meshfree-finite element interface. Many improvements were made and methods were developed that exploit the advantage of both meshfree methods and finite elements, e.g. the Moving Particle Finite Element Method (MPFEM) by Su Hao et al. or the Reproducing Kernel Element Method (RKEM) developed by the group of Prof. W.K. Liu. Meanwhile, several textbooks on meshfree methods have been published, W.K.Liu and S. Li, T. Belytschko, S.N.Atluri and some books by Prof. G.R. Liu.

Many meshfree methods were developed and applied in fracture mechanics to model arbitrary crack growth. The crack was initially modeled with the visibility criterion, i.e. the crack was considered to be opaque and the meshfree shape functions were cut at the crack surface. Later, the diffraction and transparency method was used instead of the visibility criterion since they remove certain inconsistencies of the visibility criterion. With the development of the extended finite element method (XFEM) in 1999, meshfree methods got a very strong competitor. The major drawback of meshfree methods with respect to XFEM is their higher computational cost. It is also less complex to incorporate XFEM into existing FE codes. There are still some efforts to modify meshfree methods with respect to material failure and fracture. However, it seems that much less attention is paid to the development of meshfree methods these days compared to the 90s. Nevertheless, meshfree methods still are applied frequently in many different areas, from molecular dynamics, biomechanics to fluid dynamics.

2006 TOP 10 WORLDWIDE SEMICONDUCTOR SUPPLIER RANKING ($M)

2006-08-08T20:24:00.000-07:00

Rank | Company| Headquarters | 1st half 2006 sale ($M)|

1 -- | Intel | U.S. | $ 15,255 |
2 -- | Samsung | South Korea | $ 8,946 |
3 -- | TI | U.S. | $ 6,765 |
4 -- | TSMC | Taiwan | $ 4,911 |
5 -- | Infineon | Europe | $ 4,872 |
6 -- | ST | Europe | $ 4,854 |
7 -- | Toshiba | Japan | $ 4,471 |
8 -- | Renesas | Japan | $ 4,013 |
9 -- | Hynix | South Korea | $ 3,157 |
10 -- | Freescale| U.S. | $ 3,000 |

From ElectronicNews

Meshfree Methods blog

2006-08-03T15:53:00.000-07:00

A blog dedicated to Meshfree Methods has recently been set up by the USACM Specialty Committee on Meshfree Methods. This was inspired in no small part by the work of Professor Zhigang Suo and colleagues on the Applied Mechanics blogs.

Virtual Journal of Nanoscale Science & Technology

2006-07-28T15:33:00.000-07:00

VJ virtual journal of nanoscale science and technology is a weekly virtual journal that contains articles that have appeared in one of the participating source journals and that fall within a number of contemporary topical areas in the science and technology of nanometer-scale structures. The articles are primarily those that have been published in the previous week; however, at the discretion of the editors older articles may also appear, particularly review articles. Links to other useful Web resources on nanoscale systems are also provided.

The journal provides a quick update of the current research in nanoscale science and technology. If your article is publsihed by a participating journal and it also appears in VJ, you may consider that your work has received some attentions, to say the least. You can sign up for FREE content alerts.

Mechanics of Solids and Materials

2006-07-17T10:23:00.000-07:00

This graduate level textbook by Robert J. Asaro and Vlado A. Lubarda has recently been published. The website of Cambridge University Press gives some description of the book.

Online Journal Club on Flexible Electronics

2006-07-13T08:06:00.000-07:00

In the sidebar of this blog, I've added a link to the Macroelectronics Journal Club, which was started by Teng Li using CiteULike. You may want to read Teng Li's introduction to the Journal Club. You may want to join his club, or create your own club.

e-reader is out

2006-07-10T18:56:00.000-07:00

For those who do research on macroelectronics, the e-reader has been a long awaited product. Will it really be as good as a printed book?

Note added on 11 July 2006. See also 5 new design concepts of flexible displays.

2005 AMD Honors and Awards Banquet, Orlando, Presided by Wing Kam Liu, Chair

2006-07-08T23:02:00.000-07:00

A highlight of the Applied Mechanics Annual Dinner, of the ASME International Applied Mechanics Division, is to reward distinguished members for their contributions to the field of applied mechanics.

The Mission of the Applied Mechanics Division
The Division of Applied Mechanics strives to foster the intelligent use of mechanics by engineers and to develop this science to serve the needs of the engineering community. Areas of activity cover all aspects of mechanics, irrespective of approach, including theoretical, experimental, and computational methodology. The field of mechanics, which is the study of how media responds to external stimuli, includes fundamental analytical and experimental studies in:

Biomechanics, Composite materials, Computing methods, Dynamics, Elasticity, Experimental Methods, Fluid dynamics, Fracture, Geomechanics, Hydrodynamics, Lubrication, Mechanical properties of materials, Micromechanics, Plasticity and failure, Plates and shells, Wave propagation, other related fields.

The Applied Mechanics Division is one of the oldest and largest divisions of ASME. Professor Stephen P. Timoshenko, first Chairman of the division, and others founded the Division.

The Awards of the Applied Mechanics Division

Young Investigator Award
Applied Mechanics Division Award
Daniel C. Drucker Medal
Warner T. Koiter Medal
Timoshenko Medal

Description of these awards, along with nomination forms, can be found at the AMD website. In addition, funding is being raised for a new Award, the Thomas K. Caughey Medal.

The following is a collection of photos of the 2005 winners taken at the Applied Mechanics Annual Dinner.

Professor George Haller of the Massachusetts Institute of Technology recently received the Young Investigator Award for his outstanding achievements in Applied Mechanics.
Professor Haller’s work focuses on nonlinear dynamical systems theory. Some of his numerous contributions to the field of Applied Mechanics includes the development of the energy-phase method, which is used to predict chaos in nonlinear systems, and a proof of a general criterion concerning detection of flow separation. Haller has written over fifty scientific papers. He was also named the Albert Szent-Gyorgyi Fellow in 2003 and continues to be an important contributor to the scientific community. You can read a previous entry on him in AMR.

Professor Lakshminarayanan Mahadevan of Harvard University received the Young Investigator Award for his research in nonlinear and nonequilibrium phenomena in continuum mechanics. Mahadevan’s work focuses on exploration both through experiments and theory. Observing the mechanical behavior of living and nonliving things in the everyday world, Mahadevan truly enjoys “to discover the sublime in the mundane” and through science, find the hidden truths of commonplace objects. Mahdevan has written around 70 papers concerning his work. Other honors of his include the Society of Engineering Science Young Investigator Medal (2000) and the Visiting Miller Research Professorship at Berkeley (2005-2006). You can read a previous entry on him in AMR.

Professor Carl T. Herakovich of the University of Viriginia recently received the Applied Mechanics Division Award for his significant contributions to mechanics of fibrous composite materials. Herakovich has researched a variety of composite materials including boron-epoxy, carbon-epoxy, and alumina-porous alumina fibers in a nickel matrix. He has made new discoveries on edge effects in certain materials, and has written over 130 papers to date. Herakovich formed the NASA-Virginia Tech Composites Program and has been a consultant for the National Materials Advisory Board of the National Academies for the last two years. You can read his acceptance speech delivered at the Applied Mechanics Annual Dinner.

Professor Robert Taylor of the University of California, Berkeley, received the Daniel C. Drucker Medal for his contributions to computational solid mechanics, and most notably, for the development of software for the purpose of calculating inelastic response of structures. Taylor has written over 300 works, many concerning applications of the finite element method. Taylor has elected for membership in the U.S. National Academy of Engineering for his significant contributions in computational mechanics. In addition, among numerous other honors, Taylor received the IACM Gauss-Newton Congress Medal in 2001.

Professor Raymond Ogden of the University of Glasgow received the Warner T. Koiter Medal for his outstanding achievement in the field of solid mechanics, more specifically, for his contributions in nonlinear elasticity. He has published over 170 articles and books has furthered research in areas such as the biomechanics of soft tissue and the influence of finite strain on the propagation of waves and vibrations in elastic solids. Ogden has been the editor of the IMA Journal of Applied Mathematics for the past decade and is now a member of the editorial board of the Quarterly Journal of Mechanics and Applied Mathematics.

Professor Grigory I. Barenblatt of the University of California, Berkeley received the Timoshenko Medal for his significant achievements in applied mechanics. Barenblatt’s innovation helped him form a new idea, the Barenblatt tip, about the finite material cohesion at the tip of the fracture. This new integration of cohesion with fracture became a milestone in the theory of fracture. This and other theories created by Barenblatt have made him the indisputable world leader in fracture theory. He has also made contributions in the study of porous media equation. Barenblatt’s book called “Theory of Fluid Flows through Natural Rocks” explains the problem of removal of oil from natural reservoirs and is used around the world by the petroleum engineers. You can read his acceptance speech delivered at the Applied Mechanics Annual dinner, along with a piece by Xanthippi Markenscoff.

Shaky Equilibrium - Phys Rev Focus

2006-07-08T13:48:00.000-07:00

The 'crystallization' of shaken sand-like grains matches the process in computer simulations of idealized molecules, implying that the physics of gases and fluids may apply to granular materials.

1990 Timoshenko Medal Lecture by Stephen H. Crandall

2006-07-08T05:59:00.000-07:00

The Joy of Applying Mechanics

Stephen H. Crandall, Massachusetts Institute of Technology

Text of Timoshenko Medal acceptance speech delivered at the Applied Mechanics Dinner of the 1990 Winter Annual Meeting of ASME in Dallas, Texas.

Good evening. Thank you Tom and Art for your kind introductions.

Thirty-five years ago I joined the Applied Mechanics Division of ASME. Two years later I was in the audience when the first Timoshenko medal was awarded to Stepan Prokovievich Timoshenko. I wonder how many others here tonight were also in that audience (a show of hands indicated that there were a total of twelve including the speaker). After that first medal, the Division went into high gear. In the next three years, six of the remaining giants of applied mechanics were given Timoshenko medals: Th. von Karman, G. I. Taylor, Arpad Nadai, Sir Richard Southwell, C. B. Biezeno, and Richard Grammel. Then in 1961, the Division settled down to our present steady-state operation of one medal a year. I haven't missed many AMD dinners through the years so I have had the good fortune to see most of the previous 36 awardees receive their medals. Taken together, they form an impressive cavalcade of applied mechanics. I consider it a very great honor to join this team.

I feel proud and humble at the same time. Five years ago when the late Eli Sternberg was accepting the Timoshenko medal he said, in jest, that medals, much like arthritis, were a common symptom of advancing years. I am sure that underneath that jest, deep down in his heart of hearts, Eli was just as proud as I am to receive this award.

In my case I owe a great deal to my mentor the late Jaapie Den Hartog and indirectly to his mentor before that. When I joined the ME department at MIT in 1946 Den Hartog was my first boss. Many of you already know that Den Hartog's first boss, 22 years earlier at Westinghouse, was none other than our Stepan Prokovievich. From this point of view I think you can say that I'm the first third generation Timoshenko medalist.

Many of my predecessors have taken this opportunity to reflect on the state of applied mechanics. Some have been optimistic, others pessimistic. I find myself strongly optimistic. In my time I've seen great changes in mechanics education and great changes in mechanics research. Fifty years ago in the required curriculum for mechanical engineers at MIT there were nine semesters of applied mechanics. Today there are about 2 1/2 semesters in the required curriculum which are devoted to applied mechanics. You could call that the bad news. The good news is that in these same 50 years there has been an enormous growth in the amount of applied mechanics research. The growth rate in the number of mechanics journals over the past 50 years has been substantially greater than the inflation rate in the cost of living. The growth has been in many directions. Some developments have been driven by military and industrial applications. Some developments have been driven by the desire for greater rigor. One direction of development which has flourished during my time has been the treatment of multi-discipline and multi-media problems. Forty years ago I stumbled over the idea that most engineering analysis problems fall into one of three major categories: equilibrium problems, eigenvalue problems, or propagation problems. However, when I wrote Engineering Analysis, all the examples I used were limited to single discipline problems: an elastic structure, or a compressible flow, or a thermal conduction field. The book had hardly been published when I noticed that some of my colleagues were writing about topics like thermoelasticity or electromechanics or magneto-hydrodynamics. I found myself doing research on fluid-structure interactions, on soil-structure interactions, and on random vibration which is the marriage of vibration theory with probability theory.

For the most part, the developments in mechanics are in the applications. The basic theory is pretty much in place. I often tell my dynamics students that the last major break¬through in dynamics was made by a 24-year-old Cambridge University graduate student 325 years ago. His name was Isaac Newton. This is, of course, an exaggeration. Even in classical dynamics there is some growth. We have had a significant advance during the last decade with the development of the theory of chaotic responses to deterministic excitations. I think we can look forward to changes in how mechanics education is organized and to changes in application areas for mechanics research, but I am optimistic that there will continue to be interesting and exciting things to do in mechanics.

My wife Pat has a favorite cookbook called "The Joy of Cooking". What I'd like to do now is to recount to you my views on "The Joy of Applying Mechanics". I have had the good fortune to live through a period when an academic career devoted to applied mechanics could indeed be a joy. The primary reasons for this are the teaching, the research, and the people.

First of all, mechanics is fun to teach. It has its own logical consistency. Almost everything fits, and once you get into it the density of illuminating insights is very great. I sometimes feel sorry for my colleagues in materials and design. Compared to mechanics, those subjects are very difficult to teach well.

Secondly, mechanics is fun to do research in. The thrill of turning up a new insight is an exquisite joy, whatever the discipline, but the richness of insights, at all levels, in mechanics, makes it an especially inviting field. The spectrum of opportunities ranges from abstract analysis, to computational mechanics, to experimental mechanics. One of the spectacular areas of growth that I have witnessed is that of laboratory instrumentation for research in mechanics. For many investigations the latest high-tech instrumentation is indispensable, but mechanics is perhaps unique in providing opportunities for serious work with elementary tools. For example, the most effective technique I found for displaying the salient features of a wide-band random vibration field did not involve laser holography but consisted simply of resurrecting Chladni's 150-year-old technique of sprinkling salt on the vibrating plate.

Finally, mechanics is fun because of the people. The most important people are the students and the national and international brotherhood of fellow researchers in mechanics. Students provide a wonderful stimulus to their teachers. I agree with the statement that the way to stay young is to stop looking in the mirror and to concentrate instead on the faces of the students. A great joy as one grows older is the network of colleagues sharing similar research interests that one meets at national and international meetings. The opportunities for this were greatly expanded for my generation by the invention of the jet plane.

Pat and I enjoy travelling. Our marriage began with a sabbatical year in post-war London and we have subsequently enjoyed sabbaticals in France, Mexico, Israel, and California. We have gone on lecture tours in Australia, the Soviet Union, and China. Over the years we have built up an extended family of applied mechanics friends all around the world. As a spin-off from international travelling I took up the hobby of studying foreign languages. I have enjoyed learning basic conversational skills in several languages but so far I have only reached my goal of being able to give a lecture in the language in French, Spanish, and Russian. At a birthday celebration, not too long ago, I was being "roasted" about this hobby and I would like to share with you one of the jokes they told.

A tiny mouse was running for its life with a big black cat in pursuit. Just in time it popped into its hole and went squeaking with fright to its mother. "Oh mother! There's a terrible big cat outside. It almost killed me." The mother mouse calmed her child down saying, "There, there. You're safe in here." Then she said, "Now I'll teach you a lesson." Where upon mother mouse climbed boldly out of the hole and marched right up to the cat. Looking the cat in the eye she said, "Bow Wow! Arf, Arf!" The cat was so surprised, it turned tail and ran. Mother mouse then turned to her child and said, "Now you see the advantage of having a second language!"

Well, I hope you can see that I've thoroughly enjoyed a career of applying mechanics. To have it all topped off with the Timoshenko Medal is indeed a great delight. My cup runneth over! I shall always be grateful to the Applied Mechanics Division for this heartwarming recognition from my colleagues and friends. Thank you all.

1991 Timoshenko Medal Lecture by Yuan-Cheng Fung

2006-07-01T05:49:00.000-07:00

Mechanics of Man

by Yuan-Cheng Fung, University of California, San Diego

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1991 Winter Annual Meeting of ASME in Atlanta, Georgia.

First of all, let me thank those of you who worked hard to give me this honor. I know how much effort was involved. I want to thank Dr. Saric, Dr. Bogy, and all the Committee members who indulged in me. And thank you all here this evening. To Chia Shun's remarks I am speechless. I love him as a brother. I am proud to be praised by a sibling. He is the Timoshenko Professor at the University of Michigan. With this medal I can catch up with him to honor our hero.

I am very glad to be given this Award, because Timoshenko is my hero. His books on Elasticity, Elastic Stability, and Plates and Shells are the ones I cut my teeth on. Another hero of mine is Theodor von Karman. A third one is Poiseuille, who brought fluid mechanics to medicine. They are my idols, and I am very fortunate to have been given a von Karman medal by ASCE in 1976, a Poiseuille medal by the International Society of Biorheology in 1986, and a Timoshenko medal today. I would like to speak about them. I think they have a common feature in that they developed a mechanics of man, as distinguished from a mechanics of the heaven and earth.

In character, these three men were different. Timoshenko had a father image and is more immitigable. In the first lecture I heard from Timoshenko in 1949, he talked about how brilliant St. Venant was in science and engineering. He questioned why St. Venant was so obscure in French history. He searched for the reasons long and detailed. I felt it was like listening to a tale about a lost uncle on Christmas Eve.

Another good description of Timoshenko I heard from Den Hartog in his Timoshenko Award acceptance speech. Den Hartog said that he was working under Timoshenko at Westinghouse Research Lab when he finished a paper on torsion and hesitated to publish it because he did not know whether it was important enough. Timoshenko told him, "Who do you think you are! One contributes what one can!" One contributes what one can! I like that attitude.

In a von Karman lecture I heard, he opened with a remark about himself. He said that in his youth he missed inventing the radio, in his prime age he missed inventing the airplane, in his senior years he missed inventing the nuclear reactor. In his old age he would miss the exploration of space. So he can only talk about waves, aerodynamics, and aerothermo-dynamics. As a graduate student I did not know what to make of that comment, but I remembered it. It does make sense to me now against his total contributions and ambitions. The story of his inventing the vortex street was this: He was in Gottingen and talked to Herr Hiemenz who had spent years measuring the flow behind a circular cylinder. Hiemenz could not get the flow to be stabilized. The data he obtained was always oscillating. So Karman went to work on it and wrote out the whole theory in one weekend. When he presented it at a meeting in Paris, Henri Benard said that he had photographed the vortices earlier and there were some differences between Karman's theory and the experimental results. Karman made some quick calculations on the back of an envelope, stood up to explain the differences, and suggested that the street should be called "Boulevard de Benard in Paris." Such stories make Karman inimitable.

Poiseuille was born in 1797. He attended Ecole Polytechnique and got his Doctor of Science degree at age 31 with a thesis on the measurement of blood pressure with a small bore mercury manometer. He obtained the first accurate values of blood pressure since Stephen Hales showed the way 119 years earlier (1709). Then, in 1840, at an age of 43, he published his famous paper on water flow in circular cylindrical tubes. He used pipettes of diameter 15 microns to avoid turbulence, a diameter similar to capillary blood vessels. After that he published only one other paper, on the measurement of flow with ether and mercury at the suggestion of the reviewers of his famous paper. His biographers did not know what positions he held in his life until he was 63 years old, when he became an inspector of primary schools in Paris. He died on Dec. 26, 1869 at an age of 72. He exemplifies the case that one paper makes a man.

These three men are not shy in applying mechanics to new areas. They showed that science is developed by man, and man is helped by developments in science. In hard times like this year of budget cuts, it is worth remembering this principle, because society always has a need to improve the lot of people, and engineers are the ones to deliver such improvements. And the society will always provide the needed resources.

I believe in this principle, and did not find too much conflict between personal interest and the necessity for survival. Let me tell you a little bit about myself.

I was born in China in 1919. I grew up in a period when China was very unsure of itself. My memory of my childhood was that the Christmas seasons were the time to seek refuge in the countryside, to get out of the way of the war paths of local war lords fighting for territory. I remember my family crowded in a little boat eating cold chicken. That's probably why I have liked cold chicken all my life. Later, China's problem of survival became even more difficult. In my first junior high school year, Japan took Manchuria (the September 18th event). The next year Japan invaded Shanghai (the January 28th event) and we fled to Peking. At year's end, Japan invaded She-Feng Kou and we fled back to Changchow. Students struck often to protest the government's nonresistance policy. I entered college in 1937 when the Japanese militarists started the last big push to conquer China. I chose to study aeronautics because airplanes were needed most in China's fight for survival.

In 1943, a consortium of American universities offered 20 graduate assistantships to China. The Chinese government held a national examination, selected the candidates, trained them for language, then sent them on their way. I got the position from Caltech. When I arrived in Pasadena and reported to Ernie Sechler on Jan. 6, 1946, Ernie laughed heartily by saying that the assistantship offer had expired by over two years! But he hired me as an RA. I inherited a little wind tunnel built by von Karman and Louis Dunn to study the flutter of the Tacoma Narrows suspension bridge, and was also given the job to study a drawer full of notes and scratch papers written by Tony Biot on theoretical analysis of flutter of that bridge, and to write a report about it. That was how I got into aeroelasticity. Unfortunately, von Karman had retired, Biot had gone to New York, and Dunn had gone to the Jet Propulsion Laboratory. I was left without a supervisor on aeroelasticity. Professor of mathematics Aristotle Michal took me under his wing. He taught me Frechet derivatives, with which I began my thesis on airplane dynamics.

I got my Ph.D. in Aeronautics in 1948, and stayed on the faculty. Ernie Sechler was my mentor. I have an enormous love and respect for him. Whatever I did he could show me a way to make it simpler. He was a wise counselor, and a warm friend. We worked together for 20 years on swept wing design, shell buckling, ICBM base hardening, rocket structure, fuel sloshing, etc.
In 1957, I began my self-study of physiology. I had a sabbatical leave in Gottingen, Germany. I stayed at Prandtl and von Karman's old Institution. I found its work on aeroelasticity rather dull, but the library on physiology next door was excellent. The causal factor for my going to the library was my mother's glaucoma. I translated newly published articles on glaucoma into Chinese and sent them to her in China to give to her surgeon. On returning to Caltech I began working on physiology with Sid Sobin, Wally Frasher, and Ben Zweifach. Together we wrote papers on the capillary blood vessels, red blood cells, the interaction of cells and vessels, and the mechanical properties of living soft tissues. I found continuum mechanics indispensible in clarifying these topics. In 1966, I resigned from Caltech and went to UCSD to devote full time to physiology and bioengineering.

I wanted to demonstrate that physiological problems can be solved with engineering methods. Together with Sid Sobin, I chose to work on the blood circulation in the lung. It was surprising that a thorough search of literature yielded very little reliable basic data on the pulmonary vasculature. The basic information we needed on the anatomy of the lung and biorheological properties of the materials did not exist. We had to obtain them by ourselves. Hence we had to turn ourselves into anatomists and histologists before we could use mathematical tools for physiology. The program was straightforward, but the road was long. For pulmonary circulation, it took us 12 years before we could close the first round. But we had fun on the way, and found many pretty pebbles right and left. The data we collected can be used to solve other problems. The theory worked out can be used clinically. Our patience was pretty good because a master plan existed and we knew the value of every link in the chain. But the importance of longevity became evident.

On approaching retirement, I entered another field: that of the relationship between tissue growth and physical stress. The question began at home. My wife, Luna, has a little high blood pressure which can be controlled with diazyde. But she does not like to take medicine. So she takes diazyde until her blood pressure lowers, then she stops to wait until the blood pressure rises again before taking another pill. This is not what the doctor ordered, and I wanted to know if it was a good idea. So I made a research project out of it. The project turned out to be full of surprises. For example, I found that our blood vessels remodel themselves rather quickly when the blood pressure changes. If the blood pressure was raised as a step function of time, structural change in the blood vessel wall will be detectable in one or two hours. Generally, the inner wall of the blood vessel will thicken first, doubling its thickness in two or three days. Then the outer wall thickens, and can be doubled in about 10 days. Furthermore, the residual stress in the vessel wall changes. Residual stress can be revealed by cutting a vessel segment into a ring, then cutting the ring open radially. The ring opens into a sector. The opening angles of normal arteries vary from place to place in the range of 0 to 90°, but in the aortic arch region it could be about 180°. In the pulmonary trunk it can be 360° or larger, i.e., it has so much residual stress that if it were given a chance to reach zero-stress, the vessel will turn itself inside out! Isn't that amazing! With a stepwise increase of blood pressure, the opening angle will increase first, reach a peak in 2 days, then decrease to an asymptotic value. The up and down swing of opening angle can be as large as 90-100° in some places. Our blood vessels are that alive! Associated with the structural changes, the mechanical properties change also. The constitutive equation changes with time. They are not constitutional laws at all.

These results are published in refereed medical journals such as Circulation Research, Journal of Applied Physiology, American Journal of Physiology, Journal of Biomechanical Engineering, etc., so I am not just telling you stories. You understand the mechanics instantly. I wish the medical people were as easily convinced as you are.

Fortunately, when the blood pressure is returned to normal, the changes are reversible to a large extent. Hence it appears that my wife is right. So she said, "All right. Then why don't you stop here? Why do you still talk about generalization, and more experiments? Why do you have to have a stress-growth law as you call it, sort of a constitutive equation squared?"

I offered Poiseuille as my excuse. I said, "Poiseuille knew that his paper No. 5 is his best. I still think that my next paper will be a better one. I am still experiencing my normal experience. My normal experience is something like this: A problem arises. It looks difficult. It is impossible to crack. I work on it day after day. I draw a blank. Then suddenly it becomes clear. It becomes simpler. Soon it is so simple that it is indeed trivial. I wonder why I did not see it before. So I throw the scratch paper into the waste paper basket. But the experience is pleasant. I call it life's little pleasure. I am still getting these little pleasures. But although the big one has not come, I like the little ones. That's the secret of my life I want to share with you.

Now I will conclude with sincere thanks to the Applied Mechanics Division for this heartwarming recognition from colleagues and friends. Thank you all, I wish you all the best.

Nanostructured Metals Reveal Their Secret Strengthening Mechanisms

2006-06-28T11:06:00.000-07:00

It is well known that metals are hardened by deformation and soften by annealing. How about nanostructured metals? Can we reply on conventional metal-working lore? In a paper in Science (Huang et al., Science, 312 (2006) 249), Xiaoxu Huang and colleagues at the Riso National Laboratory, Denmark and Osaka University, Japan have found that nanostructured aluminum behaves in contrast to the conventional theories; annealing makes it stronger and tougher whereas deformation (cold working) gains ductility with a trade-off of lowering the strength. The structural scale affects fundamental mechanisms of dislocation-dislocation and dislocation-interface reactions. This finding may stimulate the applied mechanics community to study the fundamental strengthening mechanisms of nanostructured materials from both experimental and theoretical approaches.

1995 Timoshenko Medal Lecture by Daniel D. Joseph

2006-06-24T06:59:00.000-07:00

by Daniel D. Joseph , University of Minnesota

In my instructions about the correct behavior of recipients of the Timoshenko Medal at this dinner, Tom Cruse wrote to me that "While I ask that you consider the hour and the length of the evening in selecting the length of your remarks, the time is yours and we are honored to hear from you at that time." This suggests to me that as a Timoshenko Medalist, I can be indulged but that if I really want to be appreciated, I should keep it short.

I understand that when Jerry Ericksen got this award, he said "thank you" and sat down. I would like to follow this courageous path, but I lack the courage and so I will embellish "thank you" just a little.

Of course, I am pleased and honored to get the Timoshenko Medal and I am especially pleased to be introduced by my teacher and dear friend, Phil Hodge. I got my Ph.D. in 1963 at the Illinois Institute of Technology in Chicago. My advisor was L.N. Tao, but I took a graduate course in continuum mechanics with Phil when I was an undergraduate. It was a very demanding and quite unusual course with an emphasis on mathematical rigor at a level at which beginning students in engineering could understand. The course had a very important and permanent influence on my understanding of the mathematics of mechanics which influences me still.

At the University of Minnesota, Phil and I were running buddies. We even ran some marathons together; that is, we started together, then I saw his backside for a few minutes and three or four hours later, I could find him well rested at the finish. I ran 22 marathons; my best time for all of them was 3:42. In that marathon, Phil did it in 3:16 and was No. 1 in his old age group. My marathon running is like my career; not much talent, but very persistent. It is good for me that the Timoshenko Medal is also given to tortoises.

Applied mechanics was very strong at IIT in the early 1960's. The late Peter Chiarulli and Max Frocht were there then, and Eli Sternberg had been there not so much earlier. Another applied mechanician, Walter Jaunzemis, taught us a very thoughtful course on analytical dynamics which I appreciated greatly. He died as a young man. It is so sad to think of these ghosts of my past. My friend, Ronald Rivlin, who thank God is still alive and feisty, told me on the occasion of my 60th birthday that I was too old to die young. This is actually some comfort. It might interest you that Barenblatt and I are editing a collected works of Rivlin which ought to appear next year.

My relations with the people of applied mechanics developed more strongly at IIT than later. Peter Chiarulli arranged for me to present some work I did about Stokes flow over a porous sphere at an ASME meeting in a session chaired by George Carrier. He introduced me as Dr. Joseph. I wasn't a Dr., but George didn't know it. Later, he told me that he always played it safe. A little later, he saved me from later embarrassment by rejecting that paper. Too many mediocre papers were published in the 1960's and 1970's.

Jim Rice noted already in his acceptance speech of last year that the early 1960's was possi¬bly the best time to get a Ph.D. in mechanics ever. Due to Sputnik, there was lots of money for fel¬lowships, new faculty positions and research. I certainly benefited from this; I got a good job eas¬ily at the University of Minnesota in 1963 and my career advanced very fast. One consequence of the atmosphere of the time was to put a bigger than usual emphasis on foundations at the expense of applications. Many engineers in those days had an exaggerated idea of the power of abstract approaches. Mathematicians, and physicists too, have a good sense of the history of their subject. They know their heroes and who to emulate. We have not this sense of history in engineering and it leaves us rudderless and prey to foreign influences like those which, in the 1960's and 70's, led to the unnatural attempt to axiomatize mechanics.

It is probable that in recent times the pendulum has swung too far against abstract approaches based in mathematics in a kind of over-reaction which generally accompanies the correction of abuses.

My career can also be understood in two phases, the first emphasizing mathematics and the second, engineering. Actually, I could point to a third phase—the sociology phase, which came first. Some of you may know that I got a master's degree in sociology from the University of Chicago in 1950. Even though I have a master's degree in this field, I don't get much respect. The problem is that no matter how well educated you may be in sociology, the man on the street has his own opinion. Engineers are much better off because they get the benefit of the doubt.

Probably only a few of you know why I got this medal. Some years ago, when I had no honors and awards but Jerry Ericksen had many, I noticed that to get them, you needed to be certified. I told Jerry that the best kind of certification is that you have already got some honors and awards from elsewhere. Jerry then noted that "every dog knows where other dogs pee."

Joking aside, I owe so much to the string of superb students who have worked with me in these past years: Luigi Preziosi, KangPing Chen, Howard Hu, Pushpendra Singh, Adam Huang, Runyuan Bai, Jimmy Feng, Todd Hesla, Mike Arney, Joe Liu, Geraldo Ribeiro, Chris Christodoulou, Oliver Riccius, Joe Than, P. Huang and many others. These students worked with me on many projects; here, I will mention two: Hyperbolicity and change of type in the flow of viscoelastic fluids and the water-lubricated pipelining of heavy crudes.

In the 1980's, together with Michael Renardy and Jean Claude Saut, I found that the unsteady vorticity equation for many models of viscoelastic fluid is hyperbolic, giving rise to waves of vorticity. In steady flows, the vorticity field can be of one type here and another there, as in transonic flow. The other variables, stresses and velocities, are neither strictly hyperbolic and/or strictly elliptic. To me, it is surprising that with so much mathematical work coming from rational mechanics in the 1960's, 70's and 80's, that the problem of the mathematical classification of type of the governing PDE's was not joined.

The key quantity in the discussion of hyperbolic waves of vorticity is the speed of shear waves. We invented a device in 1986 to measure the speed of these waves. We must have measured these speeds in 200 different fluids by now. There are over 100 values published in my 1990 book on the Fluid Dynamics of Viscoelastic Liquids. You can compute a relaxation time for these speeds, and usually it is an order of magnitude smaller than what other people get by the devices they use. I think that conventional rheometers have a too slow response, most of the signal has decayed by the time those instruments kick in.

Using speeds measured on my device, I have correlated data from our experiments on delayed die swell, the orientational change of falling bodies, the change in the drag law of air bubbles rising in viscoelastic fluids and other anomalous effects that were reported in experiments, which I interpret as a change of type. If you use the speed we measure, you get a good agreement, but not otherwise.

I must confess that the rheology community, though not hostile, seems largely indifferent to these results which I consider to be so important.

Another topic on which we have worked, which I like greatly, is water-lubricated pipelining of heavy oils. It is a gift of nature that if you put water and oil into a pipeline, and the oil is viscous enough, say, greater than 5 poise, the water will go to the walls of the pipe where it lubricates the flow. You can get drag reductions this way of the order of the viscosity ratio. Crude oils with a viscosity of 1,000 poise are not uncommon. They can't be pushed through pipes at that viscosity, but with water there, they go through easily. You've got drag reductions of the order of thousands. This is a technology which has been used and it will be used more and more.

CNN found out about our work on this and did a short video segment on it which I am going to show you. That week, I had a tooth pulled and my face was swollen. Just my luck to have a swollen face on the road to stardom.

I have been asked many times if the lubrication of one fluid by another can be described by a variational principle. Strictly speaking, it cannot; however there is something in the idea of minimum dissipation which is best expressed in anthropomorphic terms. "High viscosity liquids are lazy. Low viscosity liquids are the victims of the laziness of high viscosity liquids because they are easy to push around."

IBM, Georgia Tech break silicon speed record

2006-06-20T16:31:00.000-07:00

In this week's issue of The Solid State Technology, i.e. on June 20, 2006, IBM and the Georgia Institute of Technology announced that their researchers have demonstrated the first silicon germanium (SiGe) chip capable of operating at ~350GHz at room temperature, and >500GHz at 4.5 Kelvins. (Read more ...)

MRS Bulletin features Macroelectronics

2006-06-18T09:46:00.000-07:00

The June 2006 issue of MRS Bulletin features Macroelectronics.

The guest editor of this issue include Robert H. Reuss (program manager of DARPA's macroelectronics program), Darrel G. Hopper (principal electronics engineer at US ARFL), and Jae-Geun Park (Materials Center at Samsung Advanced Institute of Technology)

The issue include a theme review article by the guest editors and four theme technical articles covering various topics related to macroelectronics.

(via www.macroelectronics.org)

KEVLAR is a modern material with many applications

2006-06-17T08:17:00.000-07:00

1999 Timoshenko Medal Lecture by Anatol Roshko

2006-06-17T04:16:00.000-07:00

Small is Good

By Anatol Roshko, California Institute of Technology

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1999 IMECE in Nashville, TN.

David Belden’s letter announcing the award was really a surprise, almost a shock. At first I wondered whether it was another example of a story which you may have heard and which, I believe, originated in the FSU. Two friends are at a grand reception sipping cocktails when one notices a man with his chest almost completely covered with medals. Says one to the other, “Do you have any idea what those medals are for?” and the other replies, “Well, you see that one at the top left? That one was a mistake; and the others followed automatically.” I humored myself out of that thought but not out of a feeling of guilt. You see, I suddenly felt terrible that I was not a member of the ASME. There had been opportunities but somehow I had let them go by. One reason is that I was concerned about another onslaught of communications, information and other paper that always results and requires attention. Fortunately, ASME lost no time in relieving my guilt. In a few weeks I received a nice invitation and forms to fill out, and now I am Member No.6143358. And sure enough, information has begun to roll in: a beautiful, glossy magazine, notices of various meetings, etc.

I sincerely thank those who put my name forward and the Division of Applied Mechanics for this honor. I want to assure you that, though not a joiner, my destiny has always been in Applied Mechanics, as you will see as my talk progresses.

Other medalists have had some acquaintance or connection with Professor Timoshenko. Mine is mainly through the ending “-ko”. I understand that there are some who think that Tim O’Shenko was an Irishman but, as most of you know, he was Ukrainian. The “-ko” is almost certain identification. So even though I did not have the good fortune to meet Stephen Timoshenko I feel some connection.

Originally, when informed by Dr. Belden about the award and tonight’s dinner, I assumed that it was going to be appropriate to make a few acceptance remarks and that something like what I just said would do it. Not being a member, I was not familiar with the rituals of the Applied Mechanics Division. So when, a few months later, Professor Needleman informed me of the custom, I again had a bit of shock, especially when he told me it should be a NON technical talk; and no blackboard, no overhead projector! And a written copy would be needed for the Newsletter! Well, I have here my illegible hand written notes which I hope to have in printable form before the due date.

What do you want to hear in a non technical talk? Humor? Advice? An appraisal of the field and projections for the future? Views on public policy for Applied Mechanics? I’m not very good at any of that. So I’ve modelled my talk somewhat on that of Professor Willis, the 1997 Medallist, whose acceptance speech I read in the AMD Newsletter and liked very much. Some back copies were kindly provided by Professor Needleman and Mr. Majewski.

The theme is “how to pursue a satisfying career in Applied Mechanics”, and I feel very satisfied with mine. I discovered the generalized formula only at the end of my career, but perhaps someone else can use it. Simply stated it is this: “Be in the right place at the right time.” But there’s an important caveat: the places should be small. I use the term “places” as a generalization for various entities, as you will see. Hence the title of this talk.

My career started in a small high school in a small coal-mining town in the Canadian Rockies. There were 15 in the graduating class. Bellevue High School provided me with an excellent education in the basics, up to introductory calculus. The town was an ethnic pot, it was poor, everyone in it was poor, but the three high school teachers had University degrees! I still don’t know how that worked and why it doesn’t seem to work so well now, but I think one clue may be in the word “small”.

From there I went to the University of Alberta, which at that time had a total enrollment of about 2500. I was in the Civil Engineering class, some 15 in all, but on a special track called Engineering Physics, which allowed me to substitute extra Math and Physics for courses like Concrete Mixing. The Eng. Phys. option was the brainchild of Applied Mechanics professors in the Civil Engineering Department (there was no M.E. Department at that time); they were mainly in Structures and Soil Mechanics. Many of them had gone to the University of Illinois for graduate work. One of them, my good friend George Ford, an Applied Mechaniker at heart, went to Stanford to work with Goodier, the son-in-law of Timoshenko who was still very active then. So I got to know a bit about Timoshenko from George Ford, who went back to Alberta and was instrumental in establishing an M.E. Department there.

From Alberta, after some diversions, I came to Caltech for graduate work in GALCIT. This is, effectively, the department of Aeronautics, but the Division of Engineering and Applied Science does not have Departments. I guess each department would be TOO small. Lucky for me; I got to teach some of the Applied Mechanics courses that George Housner and Don Hudson had established.

In 1946 the enrollment at Caltech was about 1500, half undergrad and half gradate. After half a century it has grown to about 2000, still half and half. Bigness is not big at Caltech. You probably noticed that US News and World Report recently ranked Caltech at the top of Universities in the U.S. (even though it’s not a University!). You may have also heard, at about the same time, another education story from LA County, namely the crisis in the Los Angeles Unified School District. It’s difficult to avoid comparisons—no, not with Caltech but with Bellevue High School. In fact, one of the proposals being suggested is to break up LAUSD into smaller units. About the size of the old Bellevue School District should be about right. (This ends my venture into Public Policy.)

I was fortunate to come into the orbit of Hans Liepmann the first day I arrived at Caltech. Much of my way of seeing and doing things has been influenced by him. Hans was wary of bigness. He liked to keep things lean: big funding brings big baggage with it; you should seek funding for research you want to do, not the other way around; research must be enjoyable to be productive; “smaller” makes it easier to recover from setbacks, even crashes, and so on.

Echoing Professor Willis’ observations, I believe that a productive career in research in Academia is helped by three elements, all related to the fact that research is nurtured by questions and questioning. An ideal mix is the combination of teaching, consulting and research; the elements of this triangle feed each other constructively.
To teach technical material convincingly it is necessary to understand it, and students encourage you to do so. Digging deeply often reveals gaps not only in your own understanding but often in the subject itself. When interacting with students at the research level we teach each other. Liepmann delighted in asserting that even before a PhD thesis is finished the student should know more about his subject than anyone else, including his advisor.

The second element of the triangle which leads to questions and questioning is consulting, using this term in the broad meaning of interaction with the outside world, whether it be industrial companies, government laboratories or other societal entities. My own work was strongly influenced by such activities. Observing engineers solve tough technical problems, with imperfect technologies at their disposal, gave me a healthy respect and admiration for how they get their jobs done, and it often left me with feelings of inadequacy to help. I also realized how inadequate even our best students may be feeling as they stepped out into the real world. This led to the introduction, with Don Coles, of a new course in our curriculum, officially called Technical Fluid Mechanics but unofficially Dirty Fluid Mechanics, the kind you can’t find in textbooks. This enabled us to pass on to our future engineers and researchers some extra help; at the same time it impacted our own research, by the feedback process I’ve mentioned. I suspect that there’s also a place for a course in Dirty Solid Mechanics.

The third corner of the triangle, scientific research, is at the apex. Feynmann called it “the pleasure of finding things out”. Exhilaration may be a better describer. I feel privileged to have experienced it. Professor Oden, in his 1996 acceptance speech, said “I have experienced this phenomenon many times. I am constantly amazed by it, but find it awkward to explain or rationalize”. I had thought to give a few examples here, but there’s no blackboard or overhead projector! But I have promised to write up one of them for Applied Mechanics Reviews.

It seems to me that it is the nature of Applied Mechanics research that it is best carried out by individual investigators or small groups. So it concerns many of us that the trend is toward large consortia of researchers who are supposed to interact with each other and across disciplines. This is inevitably directed research, about which many thoughtful people were concerned when government funding of research accelerated, continuing a process that had begun during World War II. Other thoughtful people point out that this is the only way that societal expenditures on research can continue and even increase, and that anyway there is no net loss to the undirected research that would and will otherwise flourish. Perhaps this trend toward more directed research should be viewed as a contribution to the consulting corner of the triangle which I described and that individuals may still be able to work on their creative ideas under the umbrella of a large consortium. A little moonlighting might be helpful. In fact, life could be very comfortable, except possibly for the Director. But, inevitably, creative people will be left out.

Also troubling is that bigness seems to be crowding out some of the culture that has served Applied Mechanics so well, i.e. the abstraction of well-posed scientific questions from important but messy practical ones (a phrase which I’ve borrowed from Garry Brown). As someone (Prandtl?) remarked, “there is nothing so practical as a sound scientific theory”. It is idealized models, leading to analytical descriptions, that reveal the innermost workings of nature, and they help develop the “intuition” which engineers need to do their “dirty” work. This culture should not diminish; it is already small.

Mr. Chairman, again I thank you and the Division for the honor you have given me, the ASME for signing me up, and you the audience for the opportunity of speaking to you.

1962 Timoshenko Medal Lecture by Maurice A. Biot

2006-06-10T06:00:00.000-07:00

Timoshenko Lecture: Science and the Engineer

by Maurice A. Biot

As everybody knows, there are two sides to a Medal. The bright side in this case is obviously the encouragement to the recipient. The darker aspect of the other side is something you will have to bear with me. I refer, of course, to the after dinner speech.

First of all, it is a great honor to be associated with the name of Timoshenko, the Teacher, the Scholar, the great Engineer and Scientist. It is widely agreed that the high level of instruction and application of solid-state mechanics in this country is due to his influence and his teaching.

However, to me the name symbolizes much more than the award and the honor. It evokes a brilliant phase and tradition in the practice of science and engineering which unfortunately seems to be on the decline. This is the tradition of clarity, simplicity, intuitive understanding, unpretentious depth, and a shunning of the irrelevant.

There is, of course, no merit in sophistication for its own sake. In the understanding of the physical world, and particularly in the area of technological applications, it is important to perceive what is irrelevant. The level of irrelevance involves a value judgment which usually requires rather subtle habits of thought related to natural endowment and previous experience.

We should not overlook the importance of simplicity combined with depth of understanding, not only for its cultural value, but as a technological tool. It leads to quantitative predictions without laborious and costly calculations; it suggests new inventions and simple solutions of engineering problems. Aside from obvious economic advantages, it also provides an important quality in engineering design, namely reliability. In this respect one cannot help reflect on our dismal record of staggering cost and repeated failures in the field of rocketry.

Deeper physical insight combined with theoretical simplicity provides the short-cuts leading immediately to the core of extremely complex problems and to straightforward solutions. This cannot be achieved by methods which are sophisticated and ponderous even in simple cases. The process of thought which is involved here may be described as "cutting through the scientific red tape" and bypassing the slow grinding mills of formal scientific knowledge. Of course, formal knowledge is essential but, as for everything in life, the truth involves a matter of balance. The instinctive embodiment of this truth is to be found more often in the politician than in the scientist. However, it is essential to the make-up of a competent engineer.

Doubt about the engineer's function in our increasingly complex technological culture has been expressed by the blunt question "Is the engineer obsolete? Should he be replaced by the scientist"? Although such a question is the product of ignorance, the situation is such that, in this country at least, it finds a respectable echo.

What about the physicist? Speaking in general and with due respect for exceptional personalities endowed with outstanding natural ability, I think the physicist has turned away from his own tradition and has tended to become a victim of narrow specialization. Nuclear and particle physics, solid state, spectroscopy, plasma physics, all claim their victims. Many are almost totally ignorant of classical mechanics and are not able to understand the formulation of even simple problems unless it can be reduced to the solution of a Schroedinger equation.

As for the mathematician, a situation has developed which is a complete reversal of what existed in the past. Many of the great names in the history of mathematics of the nineteenth century have been those of distinguished engineers. An outstanding example is Cauchy who graduated as a civil engineer and was engaged in the practice of engineering for many years. These men were of a different breed. They had a deeper grasp of scientific knowledge, a much broader outlook than the professional mathematician of today.

Whatever the cause of this reversal we must face the fact that mathematical science has become dominated by abstract formalism. It is increasingly dehumanized and cut off from its roots in the rich and nourishing soil of physics and engineering, and the other natural sciences. What should be referred to as applied mathematics does not exist on its own, but describes essentially a function and a craft by which the science of mathematics finds its nourishment.

Much of the so-called applied mathematics which is practiced today is almost diametrically opposite to this function. It is permeated with legalistic hair-splitting, shrouded in pretentious language, as if the purpose were to obscure and surround with an aura of mystery and profundity what is very often a simple and even trivial subject.

This trend toward a formalism devoid of humanistic content, this emphasis on form at the expense of substance is found not only in science. It also prevails in our contemporary art and literature and obviously results from deeper, and perhaps self-destructive, undercurrents in our culture.

It constitutes a retrogression toward the abuses of medieval scholasticism and away from that intimate union of craftsmanship and science so characteristic of the Renaissance period. In this connection I recall a quotation from Ortega y Gasset. "Life is not to be lived for the sake of intelligence, science, culture, but the reverse; intelligence, science, culture, have no other reality than that which accrues to them as tools for life. To believe the former is to fall into the intellectualistic folly which, several times in history, has brought about the downfall of intelligence."

Generally speaking, the professional mathematician of today is a specialist in logical systems and rigor. His lack of flexibility makes him unable to exercise one of the very essential functions of mathematics in the natural sciences and engineering, which is to separate the relevant from the irrelevant, to simplify the formulation of complex phenomena, to synthesize and to unify the substance rather than the form. There is not time here to dwell on the details. For contrast let me cite only the brilliant treatment of the Navier-Stokes equations by Prandtl in his famous theory of the boundary layer.

There is, however, a more ominous aspect of this situation which brings up the matter of education of scientists and engineers. We should remember that intuitive ability closely resembles artistic talent. It may be developed or it may be smothered depending on the environment and the training. Rigor and abstract formalism are technical aspects of mathematics which may actually impede invention. They are for the specialist. The engineering student should be exposed to them only as an experience. They should not pervade his thinking nor exceed the point at which the intuitive faculties become inhibited.

In many schools the hard core of mathematical and physical knowledge is submerged in a flood of special courses characterized by abstract-formalistic overtones. There is an emphasis on formal knowledge rather than understanding and the climate is not favorable to creative talent. It should be remembered that one of the important functions of a school is to discover, encourage and develop talent and not only to transmit knowledge. To make the situation worse, we are now witnessing the introduction of the abstract axiomatic approach in high-school mathematics. Such a development involves great dangers to our future scientific and technological standing. It has been said that "Learning is the kind of ignorance distinguishing the studious." I don't want to downgrade studiousness, but I don't think knowledge should be an obstacle to understanding.

While I have dwelt on the more gloomy aspects of this situation, I would like to conclude these few remarks with a more optimistic note.

Let us hope for a revival of humanism and a spirit of synthesis in science. Let us also put new emphasis on engineering as a professional craft, requiring high skill, natural talent, deserving social recognition, and distinctly different from the scientific professions as such. New stirring are appearing in this direction. I am inclined to believe that engineers and engineering schools will play an important part in restoring the unity and central viewpoint in the natural sciences. This is because modern engineering by its very nature must be synthetic. Specialization carried to extremes is a form of death and decay.

One could formulate a principle of degradation of knowledge entirely analogous to the second principle of thermodynamics. It represents a powerful force which can be defeated only by a hard and difficult struggle. The burden of it must be carried, not by teams and organizations, but by a few individuals. In this connection there is much to be said for the smaller schools. They should provide a better environment for unhurried maturing of thought and for the nucleation process by a very small number of qualified people.

It has been customary for the recipient of an award to avail himself of the opportunity to reflect on current problems of professional interest. While I do not pretend to have brought to light any really new ideas, it seems to me that the occasion was most appropriate for their reemphasis in the framework of the Timoshenko tradition.

In this future synthesis and the revival of technological craftsmanship, I think we all agree that in the practice as well as in the teaching, engineers are called upon to play a very fruitful and essential part.

A Second-Gradient Theory of Fluid Flow

2006-06-09T05:30:00.000-07:00

Recently, Eliot Fried and Mort Gurtin have developed general balance equations and boundary conditions for second-grade materials. Their work is set to appear in the Archive for Rational Mechanics and Analysis and is presently available online (DOI: 10.1007/s00205-006-0015-7). The theory essentially blends classical work by Toupin on elastic materials with couple stresses with a modern, nonstandard principle of virtual power developed by Gurtin. Importantly, the basic formulation is independent of constitutive assumptions, and as such, applicable to both solids and fluids.

Fried and Gurtin consider incompressible fluid flow as one such application. The approach effectively generalizes the Navier-Stokes equations to include higher-order gradients of the velocity field. Through constitutive assumptions, material lengths are naturally introduced in the flow equation and higher-order boundary conditions. Fried and Gurtin refer to the former as the gradient length, L, and the latter as the adherence length, l. This work is of interest because recent simulations suggest that at sufficiently small length scales, the classical Navier-Stokes equations and their boundary conditions fail to accurately describe fluid flow. The new theory provides a mechanism to account for these length scale effects, and being continuum-based, promises to be much more efficient than discrete methods such as molecular dynamics.

In particular, Fried and Gurtin consider the case of plane Poiseuille flow and derive analytical expressions for the velocity profile. If one considers laminar flow through a channel of height h, for example, gradient effects play an increasingly important role on the flow with decreasing ratios h/L of physical to gradient lengths. A plot of the flow profiles predicted by the theory is reproduced here in the Figure to the right. The theory allows for a range of flow profiles from the limiting cases of strong (l approaching infinity) and weak (vanishing l) adherence to the classical results predicted by the Navier Stokes equations.

1974 Timoshenko Medal Lecture by Albert E. Green

2006-06-03T15:40:00.000-07:00

Reflections on 40 Years in Mechanics

Albert E. Green, 1974

Thanks to the Society through the President for the presentation of the medal.

Thanks to Dick Shield.

There is one serious disadvantage to receiving the medal – the tradition that the recipient gives an acceptance talk.

Owing to the influence of men like Professor Timoshenko, work in applied mechanics in the U.S. has mostly been centred in engineering schools but sometimes in mathematics, applied mathematics departments or institutes. In Britain theoretical work in applied mechanics has mainly been in departments of mathematics and applied mathematics, but a few departments of engineering have also been concerned with such work. My own experience in Britain has been entirely in departments of mathematics in which there were close links with pure mathematicians. In the United States I have been fortunate to be associated with colleagues at Brown University and at Berkeley, as well as visiting other universities. Although I am in a department of mathematics, both pure and applied, at Oxford, my own title is Sedleian Professor of Natural Philosophy. The Sedleian Chair was founded by Sir William Sedley who by his Will dated October 20, 1618, bequeathed the sum of ₤2,000 to the University, to be laid out in the purchase of lands for its endowment; this bequest took effect in 1621. It is regarded as the oldest of the scientific Chairs even though the Savilian Professorships of Geometry and Astronomy were endowed in 1619, and the first of them actually filled in that year. My immediate predecessors were Professor George Temple, Professor Sydney Chapman and Professor A.E.H. Love, and you will be aware that they dealt with very different aspects of natural philosophy. Professor Love held the Chair for 41 years, from 1899, and his work is well known in the present company. The fourth holder of the Chair who was appointed in 1660 was Thomas Willis. A list of some of the treatises which he wrote makes interesting reading: (1) “Of the accession of the blood”; (2) “Of musculary motion”; (3) “Of urines”; (4) “The anatomy of the brain”; (5) “The description and use of the nerves”. He also wrote about convulsive diseases, scurvy, and the comparative anatomy of some dozen species ranging from the earthworm and lobster to sheep and man. He is regarded as the founder of neurology. In his last writings on rational therapeutics he presented a vast and sometimes horrific pharmacopoeia in which, however, are buried useful descriptions of the anatomy of the blood vessels, the muscular layers of the stomach, and the detailed structure of the lungs. Perhaps we can discern the beginnings of the present fashionable subject of biomechanics in the description of the probang, an ingenious machine for treating a very rare case of a certain man of Oxford who was probably suffering from stricture of the oesophagus.

Willis had as pupils or assistants men who later became well known. They included Robert Hooke, the great inventive physicist and microscopist, John Locke, the physician-philosopher, Edmund King who, with Richard Lower, performed the first blood transfusion, and finally, Thomas Millington and Christopher Wren – who later became Savilian Professor. This set were some of the extraordinarily versatile scientists who, after their “Invisible College” as Robert Boyle termed it, eventually went on from Oxford to found the Royal Society in London – Willis was one of the original Fellows (1663).

At Oxford applied mechanics is studied in the Department of Engineering as well as in Mathematics. In this connection, Sir Richard Southwell, who received the Timoshenko Medal in 1959, held the Chair at Oxford in Engineering.

The term natural philosophy takes me back to early days in Cambridge as some of the papers in the Mathematical Tripos Examination were headed natural philosophy. On looking through the list of those who received the Timoshenko Medal I see four names associated with Cambridge. Professor Lighthill who is there at present, Professor James Goodier who was somewhat before my own time, and I did not know him in those days. Although we corresponded occasionally I only met him in recent years in California. Then there was Professor Sydney Goldstein. I attended many of his lectures both as an undergraduate and as a graduate student and I still have some excellent notes in Electromagnetism and Fluid Dynamics from him. He always packed a tremendous amount into lectures. One habit was to finish a lecture at 10am on one day in the middle of a sentence and then to begin his lecture the next day promptly at 9am continuing the same sentence as he walked in the door! He also disregarded physical disabilities. Occasionally he suffered from gout and would lecture seated on a bench with both feet and legs wrapped in bandages, using the board above as far as he could reach.

The fourth person on the list is Sir Geoffrey Taylor, or more usually known as G.I. I had the good fortune to be one of his research students and am sad to know that he is now incapacitated by illness after a long and very active life in applied mathematics and mechanics. G.I. had a room in the Cavendish Laboratory in Cambridge and he did experiments with the help of a superb technician named Thompson. Many of you will be aware of his classic work on the stability of Couette flow of a viscous fluid between rotating cylinders, which is an excellent combination of theory and experiment. The apparatus which he used for the experiment was still in the laboratory when I was a student. G.I. was an enthusiastic yachtsman and was very interested in developing an anchor which was much lighter than the conventional type and which had more efficient properties. He used to experiment with a model anchor by throwing it into a large box of sand in the laboratory with obvious enjoyment. The anchor was eventually patented and has, I believe, been widely used. Although it may now be surprising to some of my listeners I once did an experiment under his guidance – but not since then!

I recall that when I started with G.I. he suggested an area of work and discussed this with the help of rather illegible scribblings on a sheet of paper. At the end of the discussion I took the treasured paper away in the somewhat vain hope of deciphering some of the main points. Of course, G.I. really knew what answers he expected from an investigation by his somewhat unusual physical insight. I had to seek out appropriate mathematics myself and after about 9 months I was almost in despair as I had made absolutely no progress.

Before I actually started postgraduate study in 1934, G.I. sent me to the International Conference of Applied Mechanics which was held on that occasion in Cambridge. I remember being somewhat overawed by the people at the conference and I understood very little of the technical papers. Of course, being a beginner, I thought that I ought to go to every lecture! I read Professor Eric Reissner’s speech in mechanical engineering which was delivered at this gathering last year and I can endorse his remarks about “the memory of my feelings and impressions of insecurity as an early participant in technical meetings”. At the Cambridge conference I saw – at a distance – some of the well-known workers of that era in mechanics including Timoshenko, von Karman, Prandtl, Beizeno, Burgers and H. Reissner, father of Eric Reissner. For some reason I think I remember correctly that H. Reissner lectured on viscous flow between rotating non-concentric circular cylinders.

The lectures in applied mathematics for both undergraduate and graduate students in Cambridge dealt with a wide variety of subjects. It is interesting to note that many of the things we were taught in Geometry, Algebra, Analysis and Mechanics have now disappeared entirely from syllabuses in most universities! In addition to Sydney Goldstein, I attended lectures by W.R. Dean, L.A. Pars (who was my undergraduate supervisor and a superb mathematician), Eddington, Harold Jeffreys and others. I recall one lecturer who wrote very clear books and papers but was very bad at lecturing. He started with a class of ten. Very soon this was reduced to two – myself and a friend. I then dropped out but my friend persisted only to find that the lecturer did not turn up. My friend went up to the lecturer’s room in one of the colleges to find him still in bed. However, he was then given a good set of notes and went away quite content for the rest of the term.

Later when I had a Fellowship at Jesus College, I got to know people in other disciplines. One interesting person is Sir Arthur Quiller Couch – or Q as he was called – who was Professor of English and a writer of distinction. He compiled the Oxford Book of English verse and wrote many stories about Cornwall, and was once the Mayor of Fowey, a village in Cornwall. In those good old days Q would announce in the University Gazette that he would lecture on Wednesdays in this term (February 14 and March 14) – and then he cancelled one of these and hurried back to Fowey.

Another Fellow, Dr. Brittain, acted as chronicler of Q’s activities. He had two clocks in his room, one at the current time and one at God’s time, which in the summer was not the same.

After leaving Cambridge I spent some years in the Durham Colleges in the University of Durham where the department of mathematics consisted of 3 staff and I was expected to lecture on any topic of the undergraduate course in either pure or applied mathematics – something which I could not do today. If present-day staff were required to do the number of lectures per week that we had to do there would be some sort of sit-down strike or walk-out. It was many years before this situation changed. In Durham I had my first research students. One of these students worked on problems of holes in wooden materials and when he obtained his degree a friend sent him a telegram which aptly read “holes in wood wins scarlet hood”.

From Durham I went to the other, and larger, part of the University, which was at Newcastle upon Tyne (now the University of Newcastle upon Tyne) and first met Professor Shield. In those days he always seemed to be an incredibly young student. I followed two well-known applied mathematicians who had been at Newcastle for many years – Professor Havelock of water wave fame and Professor Goldsbrough who worked on tides and problems concerned with Saturn’s rings. Although they retired when I arrived I had the good fortune to know them for many years. As we know, different languages often cause many problems. I remember Havelock, who was a modest and rather shy man, being very pleased when he received a letter which said “Dear Professor Havelock, the odour of your name pervades the world”. This reminds me of a letter I received after the war from a Japanese colleague saying that he regretted the absence of correspondence owing to the prevailing darkness of the abominable days.

I had a charming pure mathematical colleague, Professor Rogosinski who hated any administrative work. He occasionally had language difficulties and after one meeting in which the future of the University was discussed he emerged and said “well, it is all a dream pipe”.
One of the great advantages of working in a scientific subject is that one gets to know many people from all over the world. I have been very fortunate in being able to work with a number of colleagues which I always find much more satisfactory than working entirely alone. It is interesting to find that similar ideas about a topic in science seem to appear in quite different parts of the world simultaneously. Having said this I am reminded that someone in the United States once remarked that no British Applied Mathematician ever believes anything has been discovered unless he re-discovers it himself!

Years ago, partly because of teaching loads in universities, there was little pressure on staff to engage in research or scholarly activity. Although this sometimes led to very dead departments or individuals, it did mean that work could be undertaken without the continual pressure of the need for publication. After the 1939-45 war interest in research in university departments greatly increased and the pressure on staff, particularly younger members, is tremendous – publish or perish has almost become the watchword. I am afraid that this tends to lead to bad standards. I particularly regret that often due recognition is not given to the type of person in a university who is a true scholar but is not one to produce a large number of papers. Such a person, who often had wide knowledge and understanding, can be invaluable in a department but gets left behind in the promotion stakes. The output of scientific papers in every subject is enormous and in recent years there has been a tremendous increase in the number of journals published. It is practically impossible to keep track of every paper in a particular area of interest, let alone in a variety of topics. As a result some duplication of effort is inevitable. Also I guess that only a small fraction of work is ever read in a thorough way.

In closing I may reflect that in mechanics, as well as in other sciences, there are fashions both in the type of work studied and in the way it is presented – the pendulum tends to swing from one extreme to the other. We all suffer from prejudices in our every day life and it is not surprising that this spills over into science. Some regard highly abstract mathematical presentations of work as being divorced from physics while others regard some aspects of physics as mere hand-waving. I believe that there is something of value in the whole range of scientific thought. Of course, intensive discussion and argument with colleagues is sometimes a very profitable – or at least a very enjoyable exercise. On looking back over the history of science one realizes that most of us can only hope to place one small brick – if that – in the edifice – and even that may get knocked out by following generations. The more one learns over the years the more one realizes how little is really known: This is always the challenge to future generations.

Strength map of carbon nanotube

2006-05-29T06:22:00.000-07:00

In theory, carbon nanotubes are 100 times stronger than steel at one-sixth the weight, but in practice, scientists have struggled make nanotubes that live up to those predictions. This is partly because there are still many unanswered questions about how nanotubes break and under what conditions.

Recently, Prof. Boris I. Yakobson at Rice University, his former postdoc Traian Dumitrica (now assistant professor at University of Minnesota), and his doctoral student Ming Hua, have developed a new computer modeling approach to create a “strength map” that plots the likelihood or probability that a carbon nanotube will break—and how it’s likely to break. Four critical variables are considered in the model: load level, load duration, temperature, and chirality. This work was published in the Proceedings of the National Adacemy of Sciences (Apr. 18, 2006 Cover feature). Full text pdf file of this paper is available here .

1980 Timoshenko Medal Lecture by Paul M. Naghdi

2006-05-27T15:36:00.000-07:00

Acceptance Speech upon Receipt of the Timoshenko Medal

Paul M. Naghdi, November 18, 1980, Chicago, Illinois

President Jones, Ladies and Gentlemen:
I would like to express my deep appreciation and gratitude for this honor, which has a very special meaning for me. Even more so, because I have personally known nearly all the previous recipients and I feel deeply honored to be included among them. I have been fortunate over the years to have met a number of distinguished people in our field (some of them are previous recipients of the Timoshenko Medal) who have been very helpful to me. Perhaps this is an appropriate time to mention a few of these people and reminisce a little.

I met Stephen Timoshenko, the first recipient of the Timoshenko Medal, when I was a graduate student at Michigan. In the late 40’s and 50’s the Department of Engineering Mechanics at the University of Michigan, as part of its graduate program, offered extensive, advanced courses in mechanics during summer school. I understood then that this arrangement of offering graduate courses during the summer was initiated by Timoshenko in the early 30’s when he was a professor there. In fact, during the summer of 1949, when I first met Timoshenko, he was a Visiting Professor at Michigan and he taught a course on the theory of plates. As you might expect, the number of people enrolled in the course was quite high – approximately 100. He was a kind person and also I recall that when someone asked him how he would grade, he could not understand how anyone could get less than an A.

I first met Norman Goodier, an early recipient of the Timoshenko Medal, when I was an undergraduate student at Cornell. As a senior in Mechanical Engineering, I took his graduate course on the theory of elasticity (I think it was called applied elasticity). Later when Norman Goodier was a professor at Stanford and I moved to Berkeley, we saw a lot of each other and became good friends. He was one of the warmest people I have ever known. We got together two or three times each year for technical discussions that were both enjoyable and inspiring for me. We had very different ways of thinking about the same subject even though we generally reached the same conclusions.

Another recipient I got to know when I was a graduate student is Sydney Goldstein. I was fortunate to have taken two courses in fluid dynamics from him when he was a visiting professor at Ann Arbor. He was a witty and stimulating teacher in the classroom with a strong sense of commitment toward his subject. He has been an instructive leader in mechanics education and research.

One of the first meetings I attended after receiving my Ph.D. was the first U.S. National Congress of Applied Mechanics in Chicago in June, 1951. I arrived there on a Sunday afternoon at the old Stevens Hotel (I think the current Conrad Hilton is the same hotel). I went to the coffee shop and found myself sitting next to Ray Mindlin. He didn’t know who I was, of course, but I recognized him, introduced myself and took advantage of the situation to ask him some questions on the theory of elasticity. He was delighted and seemed to take an interest in a young person. In fact, our discussion lasted for more than an hour. During that time I learned a great deal and got many hints that kept me busy for several months in connection with a course that I was teaching on elasticity theory.

I met Albert Green, another Timoshenko Medalist, in 1955 when he was on a lecture tour in the U.S. Later, I saw him at several international meetings and we hit it off rather well from the start. When we invited him to come to Berkeley as a visiting professor, he immediately accepted and, from my point of view, that visit led to a very exciting and profitable collaborative effort.
Another person who has been very helpful to me is Dan Drucker. When around 1952 I was first trying to set up an experiment in plasticity, Dan spent a whole day with me sharing his experiences and alerting me to the difficulties that one has to be aware of in conducting any experiment.

Now I should like to make some remarks pertaining to the teaching of mechanics and the impact of teaching on research and that of research on teaching. In the early part of my career I was rather critical of the engineering curricula of the time, including those pertaining to theoretical and applied mechanics. As the years have gone by, I have acquired more understanding. I have developed an increasing sense of admiration and respect for the engineering profession and its standards as compared to numerous other professions with which I am familiar. In recent years, I have revised my thinking about engineering curricula, especially in mechanical engineering, including the part that pertains to undergraduate and graduate instruction in mechanics. I have become highly impressed with the academic discipline and standards of the rather balanced curricula we offer to engineering students, in comparison with somewhat one-sided curricula offered by a number of other professions. Indeed, during the past few years I have often felt that other professions, such as medicine and law, could profit by examining their curricula in the light of those in engineering in general, and mechanical engineering in particular. Of course, despite the high standard and sense of commitment of the engineering profession, there is always room for further growth in striving for excellence.

Applied mechanics is an integral part of engineering but is also more than that. As an interdisciplinary subject, mechanics in its broadest sense serves not only one area but in fact all areas of engineering and a number of other areas in physical sciences as well. As teachers and leaders of mechanics, we have a responsibility to instill a sense of excitement, commitment and urgency within the profession that will set an example for younger people in the field. Quite often nowadays, one does not come away from a technical meeting with a feeling of urgency and commitment. Ideally one should come away from such meetings with a feeling that there are important and exciting problems that must be solved, contributing toward both our understanding of mechanics and the well-being of society.

Since the inception of the Applied Mechanics Division of ASME 53 years ago, the Division and its Journal have contributed much to ASME and the profession by encouraging the pursuit of mechanics and by creating a desirable identity for the field. I hope it is not presumptuous of me to make some comments about our national identity. Most of you probably know that mechanics enjoys high stature comparable to that of other basic disciplines such as physics and chemistry in Western Europe and the USSR – but the same is not true in this country. It is time for us to face the fact that we have a crisis of identity – not so much from our point of view, but from outside the discipline. For example, a large number of universities, including my own, do not have Departments of Mechanics and the visibility of mechanics is absent. Usually, mechanics faculty is a subgroup in a particular department or is diffused in two or more departments. This aspect of a name in the title of a department may not be important to most of us, but the lack of visibility creates a problem from time to time. I was told recently by responsible people in a government agency, which supports a significant portion of mechanics research in this country, that they pattern their organization after universities and in most of our universities mechanics has no visibility. It is perhaps time that the mechanics community, whether in industry or in universities, attempt to effect some changes which would at least add mechanics to the names of the existing departments.

It also seems desirable that the community as a whole be tolerant in accommodating different points of view. In fact, such diversity of viewpoints is likely to create the atmosphere of excitement necessary for vitality of the field. By different viewpoints, I do not mean lowering the standards of our profession or disregarding what we all agree to be good mechanics based on sound physical ideas. On the contrary, I am suggesting that, while maintaining high standards and good taste, different viewpoints and approaches are the essence of scientific progress; and, in fact, such different viewpoints are even more important in engineering and applied sciences than in purely basic sciences. Indeed, the history of science and engineering shows that different approaches to the same topic have led to enlightening results.

Let me mention two examples that illustrate the importance of different perspectives. When I was a graduate student, the only topics that one learned in mechanics consisted of linear elasticity, hydrodynamics and classical rigid body dynamics and the only books to study from, in addition to Timoshenko’s books, were by Love, Lamb and Whittaker. In the nearly 30 years that have elapsed, the whole picture has changed and great progress has been made in the context of nonlinear theories. But often this has not affected the teaching of mechanics at the beginning graduate level. Many of us these days find it much better to first teach finite deformation of elastic solids before embarking on the linear theory of elasticity (and this is an example of different viewpoints).

An important change that has occurred in engineering over the past 20 years is our ability to perform huge calculations by means of the computer. From the point of view of applied mechanics, this is a good thing indeed, since it allows us to deal in a fruitful manner with the rather complicated, realistic constitutive theories which may be necessary to describe some technological processes. I do feel, however, that in emphasizing the use of computers, not enough attention is being paid to the correct formulation of problems, especially when relatively simple analytical solutions are possible. I have had graduate students come to me to ask for help with their problems when all they really wanted was a system of equations that could be put on a computer. This is a serious matter in the case of engineers. If any group should understand the physical basis and the limitations of a theory, it is certainly the engineers. To have taught them that they could go on and use equations without questioning how the equations were acquired is a serious flaw in our recent educational endeavors.

On occasion one hears about the amount of mathematics that should be required in engineering curricula. Not too long ago, I heard a talk in which the question was raised of how much mathematics should one teach in order to ruin a good engineer! Of course, these words were presumably spoken in jest, but I imagine that many people may have come away with the wrong impression. I do not believe the question to ask is how much mathematics should be taught; that is similar to asking how much English should be taught. Each is essential for our profession and the answer is clear. You teach enough of these in a balanced engineering program so that the graduating engineer knows how to read and write English clearly and is able to understand mathematics well enough to function and to communicate.

I indicated earlier my belief that the community should develop more tolerance. Let me elaborate a bit more on this. Suppose I told you that it is possible to develop a theory – essentially an ordinary beam theory of Bernoulli-Euler type – that would be applicable not only to metallic structures as in problems of stability of elastic columns or vibrations of elastic beams, but also to other media such as fluid jets. On the basis of recent experiences, I know that a good many people in solid mechanics (not to mention fluid dynamicists) would be skeptical and would not look kindly on this. However, I recently came across a paper by Weber written nearly 50 years ago about an important stability problem of a viscous jet. If you examine this paper, you will see that Weber was only discussing elementary beam theory that is slightly modified and slightly dressed up. The results, which are quite good, have gained wide acceptance in the fluid dynamics community and have led to the definition of the so-called Weber number. But his method of derivation, which is basically a direct approach to the subject, seems to be largely ignored. Incidentally, this work by Weber is an example of how relatively simple mechanics can successfully serve engineering. Yet, I have not seen the problem mentioned or discussed in any elementary or intermediate level book on fluid dynamics. Imagine how exciting it would be for undergraduates at the sophomore (or junior) level to learn in the same course that the same elementary principles (momentum conservation and continuity equation) can be applied to such different but equally important engineering problems as the stability of an Euler column and the stability of a viscous jet. Here, I should like to borrow from a recent past chairman of the Division, Ronald Rivlin. In his words,

“Forward motion can continue only if the Division maintains its receptivity to new ideas and points of view.”

In conclusion, I would like to express the wish that the sense of community that one feels here tonight could be felt more often and could become the basis for us in the mechanics community to be more supportive of each other in the future.

Thank you for listening.

1992 Timoshenko Medal Lecture by Jan D. Achenbach

2006-05-20T13:14:00.000-07:00

The Wages of Wave Analysis

by Jan D. Achenbach, Northwestern University

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1992 Winter Annual Meeting of ASME.

Ladies and Gentlemen, Friends and Fellow Members of the Applied Mechanics Division, I am grateful to the Applied Mechanics Division for honoring me with the Timoshenko Medal. When I think of the past recipients of this award, I must, however, stand here with a great deal of humility.

It appears that I am the first member of a next generation, the redoubtable sputnik generation, squeezed in between the elder statesmen and the baby boomers, to receive the medal. Undoubtedly many of my contempo¬raries, who have kept the field of applied mechanics on the move, will follow soon.

Two of my favorite colleagues, Ben Freund and Dan Drucker, participated in tonight's proceedings. Ben, who was one of my first Ph.D. students, has become famous for his work on dynamic fracture. I feel some kind of vicarious pride in his achievements. Ben is a very generous person, as was obvious from his introduction. I am happy Dan Drucker was here to present the medal. I have admired Dan since my graduate student days, not only for his achievements in applied mechanics, for which he received the Timoshenko medal many years ago, but also because he has been a consistent and forceful spokesman for basic and applied research in the high councils, in which he more than anyone else in applied mechanics has taken the time and effort to participate.

Let me tell you of the experience of a colleague who passed away some years ago. He had lived a virtuous life, and he was admitted to Heaven. When he entered the Gate he was briefed by an Angel who explained to him that the pace was relaxed in Heaven. There was plenty of funding for research. Researchers were taking their time, and they studied mechanics problems carefully and in depth. So the Angel said why don't you go to work, and give a seminar a year from now. No problem, our colleague replied, I did some work on the way over here and I can give a seminar tomorrow. The Angel thought for a minute and then said: Fine, but keep one thing in mind, Timoshenko, von Karman and G. I. Taylor will be in the audience. Our colleague decided to take some more time.

In a sense Timoshenko, von Karman and G. I. Taylor, as well as all those other recipients of the medal are in the audience tonight. But then again these luminaries of applied mechanics are in that same sense always in the audience in talks that you and I may give in the AMD sessions that we are attending this week. They have set the standards. Judging from the Sessions I attended we are, however, admirably living up to these standards.

I believe I am the first recipient of the Timoshenko medal who has never seen Timoshenko in person. When I arrived at Stanford as a Graduate Student in 1959, Timoshenko, who was on the faculty, had long since retired. I never saw Timoshenko, but I certainly saw his books. They were used in courses on advanced strength of materials, elasticity, shells, stability, vibrations and dynamics. My exposure to the Timoshenko approach was sandwiched in between a more classical European viewpoint and a more modern American one. Before I came to Stanford I studied in Delft, and took courses from Biezeno and Koiter, both got the Timoshenko medal years ago. The core course in solid mechanics was then and usually still is linear elasticity. Biezeno taught elasticity broadly based on Biezeno and Grammell: "Technische Dynamik", written in German. It was an excellent course but it still was a refreshing experience to be exposed by J.N. Goodier to the Timoshenko approach. After Stanford, I went to Columbia as a Post-Doc, and I decided to listen in on elasticity as taught by Ray Mindlin and I learned a good deal more, particularly since Mindlin included the inertia term. Biezeno, Goodier and Mindlin, all three were incomparable teachers with their own style and particular interests.

If I wanted to stretch the point of connections to Timoshenko, I could tell you that my advisor (C.C. Chao) did his work with Bruno Boley, who worked for Nick Hoff, who was a Ph.D. student of Timoshenko. The genealogy is right. Time marches on.

I have always been happy that, when asked what I do for a living, I can answer I work on waves, particularly when asked by someone outside the field. Waves conjure up thoughts of possibly destructive rapidly moving energies, and visions of sweeping motions propagating towards far horizons, or deep into unknown territories.

My address tonight is entitled "The Wages of Wave Analysis'", as in the "Wages of Sin", i.e., the recompense or return. The wages have indeed been many, certainly for me, but also in an infinitely more important sense for many fields of science and technology. I gave some thought to "Riding the Waves." As you probably know this is a surfer's term which would seem appropriate for a talk in Southern California. Some of you may recall that a num¬ber of years ago there was a movie entitled "The Endless Summer", the story of some surfers who go around the world to search for the perfect wave. My activities in the field of applied mechanics, of almost thirty years, have also been an endless summer looking for the perfect wave.

I received an important exposure to waves in solids in a course taught by J.N. Goodier. The book "Stress Waves in Solids" by Harry Kolsky was the textbook. The book was then already out of print and had not yet been published as a Dover paperback. One copy in a decrepit state was available, xeroxing hardly existed and my fellow students and I copied parts of the book by hand. J believe that was the first time the thought occurred to me that there was a need for another book on waves in solids. My own book Wave Propagation in Elastic Solids was published more than ten years later. I am sure that it has been xeroxed many a time, but pardon the plug, it is still available, in paper-back form.

In this country research on waves in solids was already in bloom when I started, thanks to the work of Harry Kolsky, Julius Miklowitz and Ray Mindlin, all departed from this world, and Werner Goldschmidt and C. C. Chao still very much with us. I learned much from these gentlemen, and also from Joe Keller, as well as from contemporaries such as Y. C. Pao, Subhendu Datta and Ajit Mali. Now there is a good-size group of younger workers in the field. The Wave Propagation Committee of the Applied Mechanics Division is more active than ever before.

Over the years I have tried to advance applied mechanics techniques to analyze wave motion in solids and acoustic media in several areas of science and engineering. There were the obvious applications to impact on structures and rapid crack propagation, but there were also applications that reached further from home base to structural acoustics, seismology and quantitative ultrasonics for nondestructive evaluation. These efforts had their ups and downs. They were least successful in seismology and most successful in nondestructive evaluation. It was hard to contribute to seismology in part because seismologists are very good at wave propagation theory, and they have been initiated in the mysteries of earthquake records. There was, however, a period in the seventies and early eighties when applied mechanicians did significantly contribute to the theory of ground motion and to the understanding of earthquake mechanisms with their recently developed models of rapid crack propagation and the associated radiated wave motion.

When I became interested in non-destructive evaluation in the mid-seventies, the field was dominated by applied physicists and electrical engineers. They had excellent abilities in instrumentation and they were interested in analysis and simulation but did not want to spend a lot of time on it. They welcomed help in the area of wave analysis. The perfect match. By now I have learned something about instru¬mentation and measurement techniques and they have adopted our analytical and numerical approaches. Some of the most knowledgeable men in NDE like Don Thompson, Bruce Thompson and Laszlo Adler are among my best friends, and we happily work together.

In the quest for quality of products, especially large expensive products such as planes, bridges and nuclear reactors, and to insure safety of these products, non-destructive testing will play an important role. It is an essential part of life cycle engineering as are other areas of applied mechanics such as fracture mechanics, or in a more general sense failure mechanics, damage tolerant design philosophy and retirement for cause procedures.

I had the privilege of being introduced by a former student. I have been very fortunate with students. It is a great responsibility to find an interesting, challenging and worthwhile topic for a student to work on, particularly since it generally has to be done within the constraints of available funding for specific projects. The choice has long-range consequences for the student. Ideally advisor and student would follow Wayne Gretsky's example. When Wayne Gretsky, who is often said to best hockey player in the USA, was asked the secret of his success, he replied "I never skate to where the puck is, I skate to where it's going to be." Knowing where to go is a good idea, because as Lewis Carroll wrote: "If you don't know where you are going any road will take you there", I might add including many wrong ones. A well defined objective helps. Let me tell another little story. Two men, say a graduate student and his advisor, were looking for work. They were in a flat country, like Holland, where you can see to the horizon. They arrived at a railroad crossing where a third man happened to be standing. The two men explained that they were looking for work and asked where they could find it. The man who was asked pointed to the horizon and said: "over there where the rails get together, that's where you can find work". The two men started to walk along the track, a long way. Finally one of them, probably the professor, stopped and looked back and said "dammit we passed it".

Once a good topic has been selected, the work's progress may be characterized by different sports metaphors. One would be like a golf game where the student accurately hits a single ball from hole to hole. The role of the research advisor would be that of the caddy who carries the golf clubs, occasionally advises on the selection of an iron or a wood, warns that the terrain may be rougher than it looks, points out some slopes, warns that the edge of the sand trap is closer than it may seem and applauds the good shots. A second would be like a tennis game where student and advisor bound all over the court to hit the ball in all directions until a point is scored. The final result may be better than in the golf game. I actually prefer to play tennis. Of course many of us dream of the quarterback/running back situation where the ball is handed off by the advisor on the one yard line for a single ninety-nine yards run and a touchdown.

A few hundred years ago a wise man said "Much have I learned from my teachers, even more from my colleagues, but most of all from my students." On a more prosaic contemporary level I might add, and much do I owe to the Agencies that have made my learning possible, particularly the Mechanics Division of the Office of Naval Research and the Basic Energy Sciences Division of the Department of Energy.

As you know there are some important signs on the horizon for changes in research funding from basic to applied research. Some of these changes are already halfway here. The National Science Foundation is presently considering its future. There will be less emphasis on basic science and more on education, applied science and technology transfer. There will be a switch from DOD funding to research for civilian applications. These changes will, it seems to me, offer excellent opportunities for us in applied mechanics. Applications of mechanics pervade every area of science and technology.

A recent article in Business Week dealing with the Federal Government's move toward a new science and technology policy that puts more emphasis on "practical research" was entitled "Hey, you in the ivory tower. Come on down". I believe that we in applied mechanics have always been ready to meet on the first floor with our colleagues in industry. Interaction with industry can be very stimulating and in the future many if not all of us will become more involved with mechanics problems for industrial applications. Remember that Timoshenko worked for many years for Westinghouse and Mindlin based some of his most interesting research on the needs of Bell Labs to understand the vibration of crystals.

An effective cooperation requires, however, the participation of someone on the company's payroll. A major problem is that many medium sized and small companies have long since fired their research and development engineers, including the one that worked in applied mechanics, as part of cost-cutting efforts to improve the bottom line or the last quarterly balance sheet or to service the debt from the last hostile takeover. We at universities can contribute in an important way to strengthen R&D efforts for product development and international competitiveness, but we must have colleagues at companies to cooperate with. So hey you out there in the boardrooms and penthouses of corporate America hire some R&D engineers.

An occasion like this tends to generate retrospection. I have tried to keep it to a minimum. I know I have been very lucky. Somehow I have always stumbled into the right places, the right people and pretty much the right problems to work on. Bruno Boley crossed my path twice, the first time at Columbia, the second time at Northwestern. Back in the early sixties Bruno had an idea for post-doctoral positions that had absolutely no strings attached. They were called preceptorships and they paid better than assistant professor jobs, a princely $1000./month. The money was provided by ONR through Hal Liebowitz, who was then the director of ONR's Mechanics Division. I was one of the first beneficiaries. I used the time primarily to round off my education. After 9 months at Columbia I went to Northwestern, and years later Bruno via a detour to Cornell arrived at Northwestern to become Dean. He established an environment conducive to our research work in mechanics. Special thanks go to Bruno. I also want to thank my former and present colleagues at Northwestern for keeping me on my toes. Starting with George Herrmann, and then John Dundurs, Toshio Mura, Leon Keer, Sia Nemat-Nasser, Zdenek Bazant, Ted Belytschko, John Rudnicki and Isaac Daniel, as well as our younger colleagues, Tak Igusa, Brian Moran and Sridhar Krishnaswamy. I thank them all for providing a challenging environment.

The Applied Mechanics Division was founded in 1927 by S. P. Timoshenko. It has a great tradition. In the Sadam Hussein sense the Applied Mechanics Division is the Mother of all Divisions of the ASME. In the regular sense the Applied Mechanics Division is the Mother of several other Divisions to which it has actually given birth over the years, but the Division remains strong and fertile. The changes in the research environment which I mentioned earlier offer great opportunities to our members for a bright future. I have been a proud member of the Division for almost thirty years, and I hope to be an active member for many years to come. Thank you for honoring me with the Timoshenko Medal. Thank you very much.

New materials for next generation electronics: Researchers discover stretchable silicon

2006-05-17T07:26:00.000-07:00

After the great successes of mechanics in helping to understand failure and performance o microchips about a decade ago, a recent study underlines the importance of mechanics in electronic devices, this time for the next generation microchips that will help to sustain Moore’s law for the years to come.

A team of researchers from the University of Illinois in Urbana-Champaign (UIUC) around John Rogers (Materials Science and Engrg.) and Young Huang (Mechanical and Industrial Engrg.) have created a fully stretchable form of single-crystal silicon with micron-sized, wave-like geometries that can be used to build high-performance electronic devices on rubber substrates.

The key aspect of this new material is that it provides necessary properties to function as electronic device that can be subject to large strains. The researchers believe that this new stretchable silicon offers different capabilities than can be achieved with standard silicon chips. Applications of this material include sensors and drive electronics for integration into artificial muscles or biological tissues, structural monitors wrapped around aircraft wings, conformable skins for integrated robotic sensors, and portable electronics. The snapshot shows the wavy silicon material deposited on an elastic substrate. To create their stretchable silicon, the researchers begin by fabricating devices in the geometry of ultra-thin ribbons on a silicon wafer using procedures similar to those used in conventional electronics. Then they use specialized etching techniques to undercut the devices. The resulting ribbons of silicon are about 100 nanometers thick. In the next step, a flat rubber substrate is stretched and placed on top of the ribbons (Figure upper right). Peeling the rubber away lifts the ribbons off the wafer and leaves them adhered to the rubber surface. Releasing the stress in the rubber causes the silicon ribbons and the rubber to buckle into a series of well-defined waves that resemble an accordion (Figure below)
“The resulting system of wavy integrated device elements on rubber represents a new form of stretchable, high-performance electronics,” said Young Huang, the Shao Lee Soo Professor of Mechanical and Industrial Engineering. “The amplitude and frequency of the waves change, in a physical mechanism similar to an accordion bellows, as the system is stretched or compressed.” A nonlinear continuum mechanics analysis helped to understand these responses of the wavy silicon, for example the dependence of the wavelengths on the silicon properties and thickness, analytically. The mechanics analysis linked the maximum strain in Si ribbon to the applied strain, and therefore provided simple criteria for the development of stretchable silicon such as the maximum stretchability and compressibility.

The scientists have already fabricated wavy diodes and transistors and compared their performance with the traditional devices. Not only did the wavy devices perform as well as the rigid devices, they could be repeatedly stretched and compressed without damage, and without significantly altering their electrical properties.

Besides the unique mechanical characteristics of wavy devices, the coupling of strain to electronic and optical properties might provide opportunities to design device structures that exploit mechanically tunable, periodic variations in strain to achieve unusual responses. In addition to Rogers and Huang, co-authors of the paper were postdoctoral researcher Dahl-Young Khang and research scientist Hanqing Jiang, who will join the Arizona University as an assistant professor. The Defense Advanced Research Projects Agency Department of Energy, and the NSF-funded Nano-CEMMS Center at the University of Illinois funded the work, which was published in January, 2006 “A stretchable form of single crystal silicon for high performance electronics on rubber substrates,” Science, v 311, pp 208-212).

Mechanics of flexible macroelectronics -- an emerging field of research

2006-05-17T05:35:00.000-07:00

Flat-panel displays are rapidly replacing cathode-ray tubes as the monitors of choice for computers and televisions, a commercial success that has opened the era of macroelectronics, in which transistors and other micro-components are integrated over large areas. In addition to the flat-panel displays, other macroelectronic products include x-ray imagers, thin-film solar cells, and thin-film antennas.

Like a microelectronic product, a macroelectronic product consists of many thin-film components of small features. While microelectronics advances by miniaturizing features, macroelectronics does so by enlarging systems. Macroelectronic products today are mostly fabricated on substrates of glass or silicon; they are expensive, fragile and not readily portable when their areas are large. To reduce cost and enhance portability, future innovation will come from new choice of materials and of manufacturing processes. For example, thin-film devices on thin polymer substrates lend themselves to roll-to-roll fabrication, resulting in lightweight, rugged and flexible products. These macroelectronic products will have diverse architectures, hybrid materials, and small features. Their mechanical behavior during manufacturing and use poses significant challenges to the creation of the new technologies.

A recent review paper by Suo et al. describes ongoing work in the emerging field of research – mechanics of flexible macroelectronics, with emphasis on the mechanical behavior at the scale of individual features, and over a long time. The following topics have been discussed in the paper:

Why many macroelectronic systems will be organic/inorganic hybrid structures, and how they can be made flexible.
A way to realize stretchable electronics by using compliant thin-film patterns of stiff materials.
How to achieve high ductility of thin metal films on polymer substrates and fatigue of metal films subject to cyclic loads.
Cracking in brittle materials such as oxides, nitrides and amorphous silicon on polymer substrates.
Issues of interfacial debonding

References:

Crawford, G.P. (editor), 2005. Flexible Flat Panel Displays, Wiley, Hoboken, New York.
Nathan, A., Chalamala, B.R. (editors), 2005. Special Issues on Flexible Electronics Technology, Proc. IEEE 93, 1235-1510.
Z. Suo, J.J. Vlassak and S. Wagner, Micromechanics of macroelectronics. China Particuology 3, 321-328 (2005). (Check out the references of this paper for a comprehensive list of recent literatures in this emerging field of research)

(via www.macroelectronics.org)

The 18th Annual Robert J. Melosh Medal Competition

2006-05-16T11:28:00.000-07:00

The 18th Annual Robert J. Melosh Medal Competition for the Best Student Paper in Finite Element Analysis was held on Friday, April 28th, at Duke University. The Competition was inaugurated in 1989 to honor Professor Melosh, a pioneering researcher in finite element methods and former chairman of Civil and Environmental Engineering at Duke University. The event is made possible through generous gifts to Duke University from Elsevier, Sandia National Laboratories, and the extended Melosh family.

The Competition consists of two phases. In the first phase, candidates submit extended abstracts for consideration by the panel of judges. The names and affiliations of the authors are not provided to the judges during this phase. The competition is open to students who are no more than one year beyond the completion of a graduate degree. From the submitted abstracts, six finalists are selected to give oral presentations of their work at the Melosh Symposium. During the past few years, the Symposium has been hosted at UC Berkeley, Rensselaer Polytechnic Institute, and Duke University. The winner and Melosh Medalist is selected on the basis of the combined written and oral scores.

The Melosh finalists represent a young group of researchers with bright futures. Indeed, many of the past finalists have continued on to successful careers in computational mechanics at universities, national laboratories, and industrial research centers. The group of finalists selected for this year's competition are no exception:

Jose Andrade, Stanford University

Roman Arciniega, Texas A&M University

Homayoun Heidari, NC State University

Shanhu Li, Ohio State University

Roger Sauer, UC Berkeley

Haim Waisman, Rensselaer Polytechnic Institute

The judges for this year's Competition were Professor Tom Hughes, UT Austin, Professor JS Chen, UCLA, and Dr. William Scherzinger, from Sandia National Laboratories.

Dr. Homayoun Heidari was selected as the 18th Melosh Medalist for his paper entitled "Novel Subsurface Imaging Algorithms Based on the Finite Element Method." A list of past Melosh Medalists and judges is available at the competition website. A special issue of the journal Finite Elements in Analysis and Design will be assembled to commemorate the event.

2000 Timoshenko Medal Lecture by Rodney J. Clifton

2006-05-13T12:12:00.000-07:00

Applied Mechanics Research and Researchers

2000 Timoshenko Medal Lecture by Rodney J. Clifton

Rod Clifton
November 9, 2000

To begin, I would like to express my appreciation to the members of the Applied Mechanics Division who somehow came to the conclusion that I should be awarded the Timoshenko Medal. I would also like to thank all those who must have written letters or, through other means, provided supportive input that contributed to my being named the recipient of such a prestigious award. I hope that everyone understands that experimental research involves a team effort so that this award should be viewed as being shared by the many excellent graduate students that I have had the privilege of advising. They, along with very supportive technical staff members, are the ones who have done the experiments for the research that is being recognized by this award.

I have been in a state of shock ever since I opened the letter congratulating me on my selection. I was totally surprised. Having assumed the role of Dean of Engineering at Brown two and a half years ago, much of my thinking and energy has been focused on the needs of the Division of Engineering. The possibility of receiving such a high honor from the applied mechanics community was not even on my radar screen. Even before I became pre-occupied with administrative responsibilities, I never thought of myself as a likely choice for the Timoshenko Medal. One look at the list of prior recipients is enough to humble nearly all of us and certainly me. I am deeply grateful --- and want to move on before the Committee decides to reconsider its choice!

The talk given by the Timoshenko Medalist at the Applied Mechanics dinner is one of the few opportunities that we have to come together as a community and reflect on the challenges and opportunities of our discipline. This tradition bears some resemblance to one that I first encountered when I was an undergraduate at the University of Nebraska. I was a member of a social fraternity and at the end of our meetings we had a time for what we called "Remarks for the Good of the Fraternity". Some of the talks were really quite good, a few were very funny --- all were well intentioned. I remember one by a particularly talented English major who gave an impassioned plea for buying pink toilet paper as a way of urging us to put more emphasis on the finer qualities of life and less on such mundane issues as keeping operating costs at a minimum. While most of the talks were less memorable, I still remember the good spirit and the good intentions with which they were delivered.

My talk tonight is offered in this same spirit and can be thought of as 'remarks for the good of the applied mechanics community'. I believe that many members of our community feel that applied mechanics has come to a crossroad. As they look back they see a solid record of achievement. As they look forward they see declining student interest in our discipline, particularly among graduate students and especially among American students. As those of us who are nearing retirement age look back we see a time in the '60s when we had multiple opportunities for good jobs in universities, corporate research centers, and national labs. As some of our younger members look forward they are apprehensive about finding good jobs and those going into academic positions are concerned about obtaining financial support for a research program.

So, what do we make of this? First, we should feel good about the contributions of applied mechanics to the technological society in which we live. During this first year of the new millennium many of the professional societies have identified the outstanding contributions over the past century. On almost any of these lists one can see the supporting hand of applied mechanics. For example, the National Academy of Engineering named 20 of the greatest engineering achievements of the 20th century. Of these, approximately one-third have direct connection to applied mechanics (e.g. the automobile, the airplane, agricultural mechanization, spacecraft, household appliances, and high-performance materials) and even more have an indirect connection through the role of applied mechanics in manufacturing and in ensuring the reliability of the products being made.

Just mentioning these sectors of our economy whose development owes much to applied mechanics does not do justice to the dramatic advances that have occurred in our field over, say, the past forty years --- to choose the time since I first became a graduate student. During this time our field has been transformed by the almost unfathomable increase in computing power and its accessibility to all of us. While we have others to thank for the development of the computers, we have done our part by developing the software that makes it possible for designers to use computers to provide rational, safe, economical designs for airplanes, automobiles, spacecraft, and a wide range of other structural and mechanical systems. On the experimental side we have benefited from advances in lasers and digital electronics, for example, but here too we have developed the techniques that have turned these tools into powerful aids for measuring and understanding the flow of fluids and the deformation and failure of solids ---- from which new and better designs have emerged.

If we are so confident of our contributions in the past, why is there so much hand wringing over our future? Have we gone about as far as we can go? Have the laws of mechanics been repealed? Have they lost their importance? Have other fields become much more important? If so, do those fields not need mechanics? No, we have neither learned all that needs to be known nor have the laws of mechanics become obsolete. Our problem is not with our discipline but with the limitations that we put on it when we decide to stay with what is familiar and comfortable instead of tackling what is unfamiliar and risky. We stand on the threshold of what could be the most exciting time in mechanics since classical mechanics lost some of its luster nearly a century ago with the development of quantum mechanics.

Today we are entering a new age in biology, and a wholly new technology --- called nanotechnology --- appears to be emerging. Both areas call for new understanding from the mechanics community. In biology the greatest excitement is at the level of cells, molecules and genes. Mechanics at this level in biological systems is clearly in its infancy. Members of our community are beginning to look at the mechanics of cell membranes and even the mechanics of individual molecules. Such studies may provide the foundations for understanding how to combat viruses and how to inject drugs and genes where they are needed. While determining the structure of the DNA molecule may have been a problem in electron microscopy, understanding the operation of the DNA molecule is a problem in mechanics --- as is the great unsolved problem of the folding of proteins. Such are the problems I speak of as being unfamiliar and risky --- but possibly holding the key to great payoffs. Furthermore, from my experience in working on the restructuring of our program in biomedical engineering at Brown I believe that the biology community is receptive, even eager, for the participation of those who can make measurements and do computer simulations that will help them understand the processes that occur at the cellular and molecular level.

In the emerging world of nanotechnology we will be working with devices and even machines that are smaller than we can see with our eyes, even with the aid of an optical microscope. Deformations and motions need to be described on the scale of nanometers, i.e. on the scale of 3-4 atomic spacings. What mechanics is required to describe forces and motions at this scale? Who is best equipped to contribute at this scale? Clearly the physicists have much to contribute but so do investigators whose primary background is in applied mechanics. To me one of the exciting results of molecular dynamics and lattice dynamics has been to establish that continuum mechanics descriptions are remarkably good down to surprisingly small scales, say two atomic spacings. Boundary value problems need to be solved and who is better at solving such problems than the mechanics community that developed finite element methods.

What do we need to know to contribute to these high profile areas of opportunity? Certainly we should learn some biology and some quantum mechanics. If we are to understand the literature and interact with the researchers from other disciplines we need to know the language and the central results for the types of problems that we are considering. Progress often occurs at the interfaces between fields and we need to get across those interfaces to gain a perspective from both sides. The last four new faculty members that we have hired in the Solid Mechanics Group at Brown have been educated as physicists. One is educated as a soft matter physicist and has turned his attention to problems in cellular and molecular biology. By now all four appear to be equally comfortable doing ab initio calculations of computational physics or finite strain calculations of computational solid mechanics. To me this is the perspective that we need to see more of in mechanics. Twenty years ago when I was on sabbatical leave at Stanford I sat in on the first year courses in Applied Physics. These were courses in quantum mechanics, electrodynamics, and statistical mechanics --- all courses that I had not had before. All were truly exciting. All now seem indispensable for the challenges that I have been describing as opportunities for an applied mechanics community with a lively, stimulating intellectual curiosity.

If I were to stop here I would be leaving the impression that all of our opportunities lie in biomechanics and nanotechnology. That would be like saying all the sunshine is in Florida. We all have different perspectives on the research needs of our society and of potential contributions that applied mechanics can make. To identify a few from my perspective --- the computational design of alloys, the Holy Grail of materials science, may be achievable as computing power continues to increase and we learn better how to include chemistry and microstructural evolution in our numerical simulations. There are clearly needs and opportunities in the mechanics of thin films and functionally graded materials. Better understanding of self assembly of regular structures is an exciting area of study with great potential for valuable contributions to a number of applications. Greater involvement of mechanics in the development of electrical and optical devices is an attractive direction --- especially when there is strong coupling between the mechanical deformation fields and the electro-optical response as, for example, in the effect of strain on quantum wells. Clearly, the list of new and developing areas of mechanics research is long. Also, I have not attempted to comment on exciting directions for fluid mechanics research. From my work on hydraulic fracturing I know that much more needs to be known about the flows of non-classical fluids --- for example, slurries in which particles that are not neutrally buoyant are carried by fluids that are viscoelastic or may even be foams. From our most recent hire in fluid mechanics, a faculty member who works in microfluidics, I have learned of the challenges of trying to understand flows through micron and sub-micron openings.

I am not trying to give a comprehensive list of future directions for mechanics research. I am also not saying that there are not many attractive research directions within our traditional research areas. Certainly the talks at this meeting, and others like it, continue to provide interesting and valuable new insights. Instead, I am trying to give a few examples to make the point that mechanics has exciting opportunities, but that these opportunities often require us to move into unfamiliar areas and to do our homework so that we can take advantage of the understanding that has been developed in other disciplines.

To say just a few words about my own experiences in seeking opportunities at interfaces with other disciplines I would point to career adjustments that I made in the early ‘70s. In ‘71-’72 I spent a sabbatical leave in the Audiology Department of the Institute for Sound and Vibration Research at Southampton in England. That was my first sabbatical and I was looking for new research directions, but directions that would allow me to continue my interest in waves. At Southampton I worked on a mathematical model for waves in the inner ear. Simultaneously, I had a gas gun built at Brown for studies of the shearing and fracture resistance of materials at very high rates of deformation. The work on the inner ear was satisfying in that the stated wave guide problem was solved and insights were obtained that were interesting from a mechanics perspective. However, the model was ultimately abandoned as it did not give the right scaling laws when I tried to apply it to animals ranging in size from bats to elephants. The gas gun led to new plate impact experiments, designed from the perspective of solid mechanics, but taking advantage of the technology that had been developed by the shock wave physicists for their research on high-pressure equations of state. Essentially overnight, we had reduced the time scale of our experiments by three orders of magnitude --- from microseconds to nanoseconds. We had a grand vision: to extend mechanical testing to loading rates that were two to three orders of magnitude higher than accessible with current methods --- while at the same time simplifying the interpretation of the experiments by using plane wave loading. Those were exciting times, as I believe my former students will attest. We thought of problem after problem to which we could apply our new found capability: plastic flow and fracture of metals; rheology of lubricants; micro-cracking of ceramics; shearing resistance of compacted powders; failure waves in glasses; friction; and martensitic phase transformations. And, we could study these phenomena at the high strain rates that occur in such difficult-to-study applications as ballistic impact, high speed machining, and elastohydrodynamic lubrication.

As it turned out, the initiative on waves in the inner ear did not bear much fruit, but that of new plate impact tests for studying the mechanical behavior of materials has had immeasurable impact on the attention that our research has received. My regret is not that one initiative was not very successful, but that I did not seize more opportunities to broaden the reach of mechanics.

The potential reach of mechanics is surely very broad. Even now, mechanics enables us to understand much of our physical world and to respond to many of the physical needs of the world’s people. Aesthetically, the subject has much appeal in the sense that, when practiced well, it embodies truth, beauty, and usefulness. Mechanics is a discipline that we can be proud to be a part of and eager to share with others. It is a discipline that will remain alive and vital if we do not limit it by allowing our focus to be too narrow.
On this note, I would like to conclude by again thanking the Applied Mechanics Division for this extraordinary honor, and by thanking all of you for the attention that you have given to these remarks.

Meshfree CAD Design and Solid Remolding

2006-05-10T11:23:00.000-07:00

In the recent issue of Mechanical Engineering (May, 2006), Jean Thilmany, one of the associate editors of the journal, wrote an article, No Mesh, No Fuss, to introduce the next generation of CAD design and solid remodeling ---- the meshfree CAD design.

By throwing away the mesh, the latest meshless CAD design is claimed being faster, more efficient, and representing the future trend. So after all, meshfree methods are thriving in major engineering applications (Read more .... ).

Wikipedia and Applied Mechanics

2006-05-07T23:34:00.000-07:00

AMN: Wikipedia and Applied Mechanics

My first contribution was a new entry for R.D. Mindlin, one of the Timoshenko Medal recipients.

Whence the Force of F=ma?

2006-05-07T18:39:00.000-07:00

This is the title of a three-part series published in Physics Today by Frank Wilczek, the Herman Feshbach Professor of Physics at MIT. Prof. Wilczek is considered one of the world's most eminent theoretical physicists, and is the 2004 Nobel laureate in Physics for work he did as a graduate student at Princeton University, when he was only 21 years old.

Prof. Wilczek contributes regularly to Physics Today and to Nature, explaining topics at the frontiers of physics to wider scientific audiences. The following series of his "musing on mechanics" won the Best American Science Writing in 2005:
Whence the Force of F=ma? 1: Culture Shock
Whence the Force of F=ma? II: Rationalizations
Whence the Force of F= ma ? III: Cultural Diversity

Prof. Wilczek recently published a book named Fantastic Realities, in which 49 inspiring pieces, including the above three, of "mind journeys" are included. This book also includes contribution from his wife Betsy Devine's blog on what winning a Nobel Prize looks like from inside prizewinner's family.
You may also enjoy a recent podcast of Scientific American, in which Prof. Wilczek and his wife talk about their new book.

1997 Timoshenko Medal Lecture by John R. Willis

2006-05-06T14:18:00.000-07:00

Mechanics of Research
The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner at the 1997 IMECE.
by J. R. Willis, University of Cambridge

The award of the Timoshenko Medal is a singular and unexpected honour. I thank my friends who exaggerated my case so successfully, and promise them that I shall do my best to justify their faith in the future, even if I have not managed it in the past.

I’m not sure if I should say this, but I will. I have attended one Applied Mechanics Division Dinner previously. Bernie Budiansky received the Timoshenko Medal. I was surprised that he spoke for so long! Now I realize why. It was no ordinary after-dinner speech but the Timoshenko Lecture, and its length is prescribed. Therefore, I can only advise now that you settle down and prepare to let your thoughts wander!

A technical exposition is clearly not required, and I sought inspiration, or at least examples of how to proceed, by reading the lectures of a few previous medallists. It seemed to me that I might try to follow, in some approximate way, the path taken by George Batchelor, who was also my boss at a formative time in my career. He was founder and head of the Department of Applied Mathematics and Theoretical Physics in Cambridge.

I was fortunate enough to hold junior posts there, between 1965 and 1972, and perhaps am now even more fortunate to hold a senior post in that department. George is no longer its head but he is there every day, providing an example of dedication to research and scholarship in mechanics.

This, in fact, will be my theme: how does a career develop, in which perhaps the most significant component is research? Naturally, this will relate to applied mathematics and mechanics, because that is all that I know.

The main focus of George’s lecture was how an institution should be organised to stimulate invention and research, and I shall try to address a somewhat similar question.

Yapa Rajapakse asked me the other night what would be the title of my talk. I told him that I hadn’t given one, but perhaps an appropriate title would be “Mechanics of Research”. My concern will be how an individual should position himself or herself, to do fruitful research. So, in particular, what should someone just starting out do, and expect?

To begin, it pays to be good at passing exams. Otherwise, acceptance in a good research school is likely to be difficult. It pays also to have a thesis adviser who has the right sense of what might be important in the future as well as tractable now, with the right amount of effort. This is not always so easy to achieve. Paul Matthews, a physicist of great distinction (I knew him when he was Vice-Chancellor of the University of Bath, where I spent many happy years as a Professor), told me that, when he was a young research student in the Cavendish Laboratory, he one day approached Paul Dirac and asked him if he might be willing to supervise his research. Dirac’s response, utterly sincere and modest, was that he didn’t need any help with his problems at that time.

Few of us have the opportunity to acquire such an anecdote. There is, however, an uncomfortable lesson to be learned by all at this stage. Being clever may be necessary, but it certainly is not sufficient! It is still more important to have commitment and true interest in what you are doing. While a bit of competitive spirit is surely no bad thing (and may be almost essential), the pleasure of achievement against your own standards should be -- probably has to be -- your main reward, since it is certain, whoever you are, that you will see people around you who have more talent, and have done much more significant research than you are ever likely to do yourself. I am reminded here of another story I was once told. I am not sure now whether it was told me by Jock Eshelby, or about him: as a young research student, he went to see a great elder statesman of solid state physics, and asked what were the really significant areas in which an aspiring researcher should concentrate. The reply was, “I don’t know. And if I did, I wouldn’t tell you!”. Or perhaps Jock was the elder statesman: those that knew him can surely imagine him making such a response, mixing humour with truth! The fact is that, unless you are exceptionally lucky, you have to have your own ideas and be satisfied with them.

Having done your first research, and obtained your PhD, the next problem is to find a position which will allow your research to flourish. I wish I could advise here. My own experience is useless, since when I was at that stage, there were more good jobs than there were people to fill them, and I remember with appreciation one of the services my thesis adviser, Maurice Jaswon, rendered at that time. He took sabbatical leave in the USA, and I was able to monitor some of his movements from job offers that I received. I actually took a post-doctoral position at the Courant Institute, New York, and had the benefit of learning from some of the greats of applied mathematics, including Joe Keller, another Timoshenko Medallist. There are two problems now, or so it seems to me.

One is that jobs are scarce. The other is that there is pressure to behave immediately as though you are a great leader, attract research funds and perhaps have more graduate students than is comfortable for you or them. I do believe that foundations have to be laid, by personal study and contemplation. Better to become a motivator and facilitator later! And in any case, you won’t survive long-term as a generator of ideas, unless you are doing quite a bit of research personally. Clearly, these days, some compromise is necessary. I would like to think that talent is recognised not only by amounts of money attracted, or numbers of publications, though it would be quite wrong to infer that independence from these activities as demonstrated by failure to deliver necessarily implies true commitment, or ability, or depth. A positive aspect of the grant culture is that research driven by practical concerns can have fundamental significance and, even when it does not, involvement in such research can provide a perspective from which important generic or fundamental problems may be identified.

Assuming that you keep going successfully, and achieve a senior position either in a University or a Research Department, you surely will acquire wider responsibilities. These are likely to include responsibility for the welfare (and livelihood) of others, and may also involve administration concerning the research infrastructure of your discipline.

I think particularly here of activities relating to publishing. We almost all act as referees (except for those — some very distinguished — who just don’t respond!) and some of us act as journal editors.

I have to admit that I sometimes suspect that people these days write more than they read -- including, in some cases, papers upon which the person’s name appears as author! But enough of that, and back to the functions of an editor. This is not a research activity, but (I do my best to remind myself) it does make an important contribution to the collective scientific endeavour. Furthermore, although you certainly can’t please everyone all the time, it is my experience that the job can make you more friends than enemies. The thing to remember is that you can’t know everything, so you must take the best advice that you can find and then (even when the advice is inadequate, as it can be on occasions!) take a decision in as honest a fashion as you can. Just occasionally, you may have the opportunity to promote some of the first work of someone destined to be a star. This is a real satisfaction. And this reminds me of something else that goes with age and seniority: if you become a head of department -- or similar -- and have the opportunity to make appointments, you must never be afraid of appointing someone you suspect may be better than yourself. I have done this many times. Not only is it essential for the well-being of your unit, but you actually derive credit as well as benefit for your own research.

I realize that I started with the intention of making general comment but have lapsed into personal reminiscence. Now I would like to do this still more explicitly. Certainly the progress of my career has been influenced greatly by various colleagues that I have had. After NYU, I went to Cambridge on the initiative of Rodney Hill.

Of course he is impossible to emulate, but I saw an example towards which to aspire. Also at Cambridge, I interacted with Jock Eshelby, whose papers had already been one of the foundations of my education. I always knew that my main contribution would be mathematical, and I learned important lessons from Gerard Friedlander and Edward Fraenkel in particular.

When I was still relatively young, I moved to the then new University of Bath. Over the next few years, I had the great good fortune to appoint outstanding colleagues, and I learned some more mathematics particularly from John Toland. I also had several excellent students and post-docs. In particular, David Talbot was my student more than 20 years ago. He is still a major collaborator and I am happy to acknowledge my debt to him. One of my best post-docs was Pedro Ponte Castañeda.

Again, we have interacted over the succeeding years to my distinct advantage. When I first returned to Cambridge, I was fortunate to have Pedro as one of my early visitors. Another was Walt Drugan, who was never my student or post-doc but I wish he had been. This is one of the advantages of working in a location that others consider attractive. In the three and a half years I have been back, I have had the benefit of a succession of distinguished long-term visitors including, besides Pedro and Walt, Huajian Gao and Zvi Hashin. I have also, in recent years, done my own share of travelling, and my most frequent single destination has been the laboratory of Sia Nemat-Nasser, where there is always something new and exciting for me to learn.

Travelling and editing a journal do not form an ideal mixture, and would have been much more difficult to combine if I had not had the fortune to have Ben Freund as an outstanding co-editor of JMPS. During periods that I am away, he continues -- I expect -to feed copy to the press, so that short absence is not a problem.

One of the most significant world events of the last few years had impact on me and my research too: the demise of the Soviet Union made available many researchers of great ability, prepared to take more junior positions than objectively they deserved. In my case, I had successively as post-docs Sasha Movchan, Valery Smyshlyaev and Natasha Movchan. I can only liken working with them to driving a powerful car: you touch the accelerator and really move! They all three now have secure positions and do not need me, but still we collaborate, and I get (some of) the credit for their hard work and talent.

This, perhaps, leads me to my final piece of advice: when you get the chance, collaborate with talented younger researchers as much as you can. Few activities can be more rewarding. In my case, this goes a long way towards explaining my presence this evening. Now I would like to conclude, expressing my deep gratitude to all those with whom I have had the good fortune to interact during my career so far, coupled with keen anticipation of more in the future.

Song-Ping Zhu Has Found An Exact Solution for the Black-Scholes Equation

2006-05-02T12:44:00.000-07:00

Prof. Song-Ping Zhu at University of Wollongong, Austrialia, has recently found another exact solution of celebrated Black-Scholes equation that corresponds to the so-called American option, which has long been regarded as an outstanding problem in finance mathematics modeling, and it has been hailded as a holy grail in mathematics.

The so-called Black-Scholes equation derived by Fischer Black and Myron Scholes in 1973 is the mathematical model for valuation of option. Prior to Zhu's solution, the only existing exact solution of Black-Scholes equation was the solution corrsponding to the so-called European option, which was found by Fischer Black and Myron Scholes in 1970s. This solution has been widely accepted by the financial market as a guide for pricing for the European options. Over time the significance of their discovery was fully recognized, and in 1997 the Nobel Prize for Economics was awarded to Myron Scholes and Robert Merton. (Merton worked in a similar area at about the same time. Black died in 1995 and Nobel Prizes are not awarded posthumously). However, in today’s financial markets worldwide, popularly traded options are of American style. Unlike European options, American options can be exercised at anytime prior to expiry.

Zhu's findings have triggered widespread excitement among his mathematical colleagues who are confident that this long-standing problem has finally been solved. Professor Zhu has now had his journal paper, “An Explicit and Exact Solution of the Value of American Put and its Optimal Exercise Boundary” accepted for publication in the journal, Quantitative Finance.
(See the press release).

Added Notes: Prof. Song Ping Zhu, my childhood friend, is a fluid mechanician, who obtained a PhD degree in applied mechanics in late 1980s from University of Michigan at Ann Arbor. Dr. Zhu is the last PhD student of the late Professor Chia-Shun Yih.

1998 Timoshenko Medal Lecture by Olgierd C. Zienkiewicz

2006-04-29T13:12:00.000-07:00

AS I REMEMBER
by O. C. Zienkiewicz, University of Wales, Swansea

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1998 IMECE in Anaheim, California.

1. Introduction
It is a great pleasure and honour to be included in the distinguished list of recipients of the Stephen Timoshenko Medal. I would like to take this opportunity to thank the American Society of Mechanical Engineers and the various friends I have in it who must have been responsible for my selection.

Because of my age and my long involvement in the field I know personally, or have known, more than half of the previous recipients of this award. Indeed, the very first recipient and namesake of the award, Stephen Timoshenko, was one of these. We met in 1960 at Northwestern University when he visited one of his early doctoral students, much distinguished in the field, Professor Nick Hetenyi. Both of these acquaintances are now gone, having worked long and contributed much to the subject of applied mechanics. In the long list of recipients, now departed, I find my own Ph.D. supervisor, Sir Richard Southwe1l, and an old adviser and friend, Professor William Prager. Amongst those no longer here is another friend, James Lighthill. Though he received his medal as early as 1963, he was still healthy and fit this year. But many may not know that it is only a few months ago that he met his end – trying to swim round the Island of Sark in the Channel islands, a feat much younger men would not attempt and which he, using his knowledge of the tides, previously accomplished more than once. I salute his courage and achievements.

2. Timoshenko: teaching and research
Though my first personal encounter with Stephen was in 1960, he was well known to me by that time. In my Ph.D. studies, which started in 1943, his book on Theory of Elasticity became my bible. At the outset of my study with Professors Pippard and Southwell I had to acquaint myself with the earlier numerical solutions produced in 1910 by J. F. Richardson. As that work used the Airy stress function to formulate the solution, some introduction to elasticity was clearly necessary. I had many gaps in my knowledge having just completed the very brief, two-year, wartime degree at Imperial College. Therefore, after some unsuccessful encounters with various texts I followed the recommendation of a senior colleague and invested in Timoshenko’s famous book, which today still holds a privileged place in my library. That text solved my problem completely. In the first two chapters I found all that was needed and it was only his excellent presentation which made me read further.

This episode - and indeed later contact with the works of Timoshenko - made two important impressions on me. First, I realised that even quite complex ideas could be presented in a lucid form. This was most helpful to me later when I was compiling my own first book on the finite element method. Of course this was some 20 years later, but I have always tried to follow the master by avoiding the alternative process, very popular among some scientific writers. They follow the maxim quite probably coined by a German philosopher, which simply said: “Warum einfach machen wenn man auch kompliziert sein kann.”

Second, which perhaps took me longer to realise, was the fact that good teaching cannot be practised properly without underlying research. Certainly the example of Timoshenko provided an example for me when I became a young teacher.

The conflict between the two directions of teaching and research, still much discussed in Academia, was originally the subject that I wanted to discuss in this talk - but, enough has been said on this matter. It was after reading Timoshenko’s autobiography that I changed my mind and in true “plagiaristic” spirit I adopted his title for the present talk – “As I Remember”. This will allow me (1) to reminisce a little on my own origins and (2) to discuss the development of my own research and how this led to my present involvement with the finite element method.

3. As I remember - the linking of life's strands
Timoshenko’s autobiography was written in Paris in 1963 and was translated into English with his help five years later when he reached the ripe old age of 90. Reading this book was a most interesting experience, especially when I realised that our own life’s strands were interlinked and even intersected on many occasions. Timoshenko was born in the Ukraine in 1878, five years after the birth of my father. The places of their birth, as far as I can trace from the available atlases, were about 100 miles apart and each a similar distance from Kiev. Both of them were citizens of Imperial Russia at the time of their birth, but their nationalities were different. Timoshenko was basically Ukrainian and my father was Polish - both facts quite well recognized at that time when nationalities and citizenships were separate entities.

Though my father was a lawyer and Timoshenko an engineer, it is interesting to speculate whether their paths at one time or another crossed. Certainly, for a limited period both of them lived in Kiev and it is also certain that during later years both were much involved with St. Petersburg where, after the Revolution, the first liberal, provisional government in Russia was formed under the premiership of Kerenski.

It was during that provisional government time that the divergence of their paths occurred. My father, perhaps because of his English wife and knowledge of the English language, was chosen to be the Consul in England of Kerenski’s provisional Russian government. However, my father was stranded and started a new life when the Bolshevik revolution erupted in Russia. It was in England that both my sister and I were born. Timoshenko, on the other hand, left Russia by a completely different route. This led him later, via Turkey and Serbia to Zagreb in Croatia where he became a professor at the Technical University for some time, before moving finally to the U.S.A. in 1922.

Those who read his autobiography will find full details of the adventures of his life at that time, and the story of his rise to fame in the American continent and indeed in Europe. He first established his position firmly as an engineer and teacher at Westinghouse, then became a professor at the University of Michigan in Ann Arbor in 1927. Finally, in 1936 he reached Stanford University. The Chair he held there became his last permanent employment although he finished his life in Switzerland - a country he had much loved in his younger days.

So how did our life strands interlink again? Well, I have already mentioned the importance of his text in producing my doctoral work under Professors Pippard and Southwell. It is through the work of the latter that the connection will arise again. Professor (later Sir) Richard Southwell was, at the time of my doctorate studies, leading a research team concerned with the solution of finite difference equations in elasticity for various problems of realistic application. Indeed many of these problems were concerned with the war effort and therefore confidential. Others were not - like my own analysis of a dam - though the methodology was not publishable during the war. Even the proceedings of the Royal Society were at that time “confidential”. It was then that I acquired a general interest, not only in elasticity, but also in fluid mechanics, which to Sir Richard presented just one more problem to be dealt with by a general numerical procedure.

It happened that Southwell was one of Timoshenko’s guests at the University of Michigan as early as 1935. This in turn led to a later encounter after the war in 1949 and again at Ann Arbor. At Timoshenko’s invitation both were involved in a summer course and this meeting was to be more important. Certainly Timoshenko was always the engineer, and being at that stage engaged in the quantitative solution of problems, he was much impressed by the generality which was established by using numerical, finite difference solutions. I believe this caused him to write an extensive appendix when the second edition of his book on Theory of Elasticity, now co-authored by J. N. Goodier, appeared in 1951. This appendix included a full description of Southwell’s procedures and solutions. He remained at all times a protagonist of numerical solutions, and it was here that our interests began to overlap.

4. The engineering beginnings of numerical analysis
The first finite difference solutions of equations of elasticity dated back to the work of Runge in 1908 and Richardson in 1910. The latter indeed solved the problem of stress distribution in a gravity dam, a subject of much interest at the time in view of the construction of the Aswan Dam in Egypt. Indeed, during the same period, inconsistencies and difficulties of using standard, “cantilever” approximations were realised and a true elastic solution was obviously needed to settle the controversy.

As Southwell’s relaxation methods were available, Professor Pippard - my doctoral Supervisor - set me the goal of providing a very accurate answer to the above question. I was eventually successful and in 1945 I duly handed in my thesis solving that problem, as well as others on meshes very much finer than those initially used by Richardson. The success was due to the use of relaxation methods, but why were they so successful and where-in lay their magic?

It is my belief that the ideas introduced by Southwell, which were of considerable importance, could be summarised as:

The recognition that the finite difference equations could be made equivalent to an analogous discrete structural system, and
The solution of the structural discrete system could be performed most efficiently by an iterative process.

As is well known, discrete structural systems, which provide the basic work for all civil, aeronautical and structural engineers, can be formulated using either the so-called “displacement” method or the “force” method. The first of these methods is obvious and direct, though it is well known that the second (the force method) is also useful in many simple cases of redundant structures for which it provides an economical and elegant solution. It is difficult to say who first formulated the direct displacement (or direct stiffness) approach. Certainly the method was well known at the beginning of this century and certainly it was included in the education of engineers in the 1930’s. In this approach stiffness coefficients were obtained for each element of the structure and the system equation was obtained by a simple addition of such coefficients. Matrix ideas were useful in this process and certainly provided a shorthand. They were not, however, essential to the understanding or indeed to the solution of the equations. Fraser, Duncan and Collar in the 1930’s appeared to be the first to use matrices for such problems in structural engineering in the aeronautical industry.

The procedures used in the direct stiffness approach were precisely the same for many other engineering systems, typically those that occurred in the solution of pipe network systems or electric networks. In each of these exactly the same formulation applied and in all cases the procedures were the same. It is therefore worthwhile to talk about a standard discrete system in this context and we observe in the literature a rapid diffusion of ideas from one area of application to another.

Southwell’s method of relaxation used for iterative solution of structures, or similar problems formulated in a discrete system, was a procedure he named “systematic relaxation of constraints” in 1934. In this process, each “nodal” displacement or similar system quantity was first assumed to be fixed in an arbitrary position by imaginary constraints (which he often described as “jacks”). On “relaxing” of such a constraint by removing the “jack”, the load was transferred to adjacent nodes and the node in question then was displaced by an amount which was easily calculable. Obviously, in the continuing process of constraint relaxation the load transfer in the structure would ultimately lead to correct solutions when all the load was thus transferred to the supports.

Mathematically, of course, the procedure was carried out in a sequence similar to that of the Gauss-Seidel iteration, but in a manner guided by the user. However, the physical interpretation of the process made it very understandable and such methods as moving a whole group of nodes simultaneously etc. could be used effectually by an intelligent operator to accelerate convergence.

The “structural” relaxation procedure of the Southwell type was apparently used as early as 1922 in Zagreb by a man called Calisev, (viz. Timoshenko). However, much more important was the development of the so-called “method of moment distribution” by Hardy Cross in the U.S.A. in 1932. This preceded the Southwell process by only two years but the Hardy Cross Method gained fame internationally and became the standard process for solution of framed buildings, etc. in the 1930’s and 1940’s.

It is of interest to make a marginal remark that there is a good reason for the success of the Hardy Cross moment distribution method vis-à-vis the Southwell relaxation method then applied to tension bar structures. The “carry over” factor in bending computations was one half rather than unity in bar structures and this of course led to a very much more rapid convergence.

When Southwell entered the area of finite difference computations he generally endowed the discrete equations with a structural interpretation. Thus the Poisson equation, which was well known could represent the deformation of stretched membrane, became in the finite difference net the deformation of a string net with given tensions. The string net being a simple structure could of course be solved by precisely thesame procedures as Southwell applied earlier to actual discrete structures and thus the Systematic Relaxation Constraints of 1934 could be used again.

It is of interest to note that such a physical interpretation of finite difference equations, when used for elasticity, was simultaneously and independently derived in the U.S.A. The conditions of wartime secrecy and the resulting restrictions on exchange of documents prevented Southwell’s work with this being widely known there. However, two important developments were derived in the U.S.A. The first one was arrived at by Hrenikoff who in 1941 established a so-called framework analogy to the finite difference equations of elasticity, and the second was arrived at by McHenry who in 1943 presented the lattice analogy. Clearly engineers liked this physical manner of interpreting equations which also simplified boundary conditions which were now purely physical. These analogue procedures were the precursor of the concept of finite elements.

In the classic paper of 1956, Turner, Clough, Martin and Topp presented the idea of dividing the real continuum directly into elements of arbitrary shape and directly establishing their stiffness. This became known as the method of Finite Elements only in 1960, following a paper presented by Ray Clough. In the original work very explicit physical models were used, thus completely avoiding the writing down of either finite difference or differential equations.

Much later the finite element method was to become based on the use of variational or weighted residual procedures of Galerkin type applied directly to the differential equations used to model rationally the elements of a continuum. Though most engineers applied this initially to the elasticity equations, it must be remarked that Courant did this much earlier in 1943 - i.e. precisely when Southwell, Hrenikoff and McHenry were active. In his work he showed that such direct procedures could be used for the Poisson equation. Courant introduced what is essentially the same linear triangle as that derived in 1956. Being, however, a mathematician he did not see the need nor did he have the desire to seek a physical interpretation.This perhaps accounts for the fact that his work was only unearthed several years after the mainstream engineers had been happily using the finite element procedure for solving their structural problems.

5. Is F.E.M.'s success due to its intuitive appeal or its generality?
There is no doubt that it is the intuitive appeal of the finite element process which makes it so popular today. When in the late 1950s I met Ray Clough and for the first time encountered his idea of splitting a continuum into “physical lumps”, the procedure did not appeal to me. Surely it all could be done more precisely and conveniently with finite processes I learned from Southwell and used successfully over many years? We did, however, agree that one problem remained which needed solution. That problem was the analysis of shells of arbitrary shape as these were much encountered at the time in the design of arch dams and in architectural flights of fancy.

The twin difficulties of the finite difference approach that I had been using were: (a) deciding which set of governing equations to use. Here the choice was wide with many authors contributing different approximations, and (b) establishing analytically the co-ordinates of an arbitrary shell in which the governing equations were to be approximated.

Both Ray and I agreed that here the finite element approach could well be used, employing as elements flat facets of a triangular or rectangular shape with the former of course being needed for arbitrary shells. In such a manner both difficulties could be simultaneously avoided.

For such a finite element formulation the “inplane” stiffnesses were already well established and surely the corresponding bending stiffnesses based on the Kirchhoff thin plate theory could easily be added.

It was on these problems that Ray’s and my own research students spent much time during the early 1960’s. By 1965 both of the groups were successful and found suitable formulations for triangular plates. Two years later they established the possibility, and indeed were successful in solving arbitrarily shaped shells. The thin shell modelling by flat facets proved convergent despite a few variational crimes committed on the way, but both the problem and its solution were overtaken by events which occurred in parallel.

My colleague, Bruce Irons, and myself also developed in 1965 the first three-dimensional solution using higher order elements, which could be curved by an isoparametric mapping to fit almost any shape. Clearly, by making such elements thin, any curved shell or plate could be modelled without introducing the super-human efforts needed to establish Cl continuity or the necessity of introducing thin plate and shell theory assumptions.

This development resulted in the fact that by the end of the decade the thin plate and shell problem disappeared, being today largely of historical interest. But many difficulties still were encountered in establishing a robust formulation. I shall not dwell on them except to say that by the mid-1980s all of these were overcome.

Did intuition or mathematics drive the second development to success? Who knows? But without the proper and precise use of mathematics the present case of dealing with thin wall structures would not exist. Further, the developments of rational approaches to such new fields as those of fluid mechanics, electro-magnetism, etc. would not be possible. Which way should we direct our research now ?

6. Which way now?
It is recognised by many that the finite element process of today is but a particular form of the weighted residual approach. The latter was classified well by Stephen Crandall in his excellent book of 1955, though the fundamentals were established by Galerkin somewhat earlier in 1915. (This occurred I believe in St. Petersburg and must have coincided with the time Stephen Timoshenko was there!)

The difference between the various approximation procedures that are today still used is that of the specific trial or weighting functions that are employed. Much of the research done today centres on finding better, newer, and more efficient designs.

Von Karman said:

“The Scientist studies what is, the engineer creates what has never been.”

Surely this requires more efficient analysis procedures to design what “never has been”.

Charles H. Duell, commissioner of U.S. Office of Patents in 1899 mentioned at the time that

“Everything that can be invented has been invented.”

I do not share this pessimistic view and I think we shall see many exciting developments in the coming years. It is evident that both applied mechanicians and mathematicians will continue to contribute to the numerical analysis field.

However, I have reservations about making predictions for the future, especially since in public speeches these may lead to such mistakes as the famous one of Thomas Watson, Chairman of IBM in 1943. His prediction was that

“I think there is a world market for maybe five computers.”

. . . . probably more than a trivial miscalculation.

This could only be rivalled, however, by a statement by the famous British scientist, Lord Kelvin, who was the President of the Royal Society in 1895 and apparently said:

“Heavier-than-air flying machines are impossible. ”

Perhaps silence on matters of predicting the future is golden – and here I shall rest.

Ranking of Mechanics Related Journals (2004)

2006-04-24T21:51:00.000-07:00

Based on a survey from Journal Citation Report (JCR),
we listed below the 2004 Journal Impact Factors (IF) for some
mechanics and materials related scientific journals.
Our list and information are not complete. We welcome
readers' input, comments, and information.
We also caution readers that using IF as the sole criterion to rank scientific journals' academic reputation may not be objective nor true to a journal's actual scientific merits.

-------------------------------------------------------------------
1. Nature : 32.182
2. Science : 31.853
3. Solid State Phys. : 16.000
4. Nature Materials : 13.531
5. Nano Letters: 8.449
6. Physical Review Letters: 7.218
7. Advanced Materials: 6.801
8. ANNU REV FLUID MECH :6.694
9. Applied Physics Letters: 4.308
10. ADV APPL MECH : 4.000
11. INT J PLASTICITY: 3.819
12. Acta Materialia: 3.49
13. Physical Review B: 3.49
14. MRS Bulletin: 3.444
15. J MECH PHYS SOLIDS : 3.443
16. Physical Review A: 2.902
17. J RHEOL :2.525
18. Geophysical Research Letters: 2.378
19. Journal of Applied Physics: 2.255
20. J MICROMECH MICROENG : 2.048
21. Geophysical Journal International: 2.014
22. J. Biomechanics: 1.911
23. GRANUL MATTER : 1.897
24. J NON-NEWTON FLUID : 1.862
25. J FLUID MECH : 1.853
26. J NONLINEAR SCI : 1.850
27. ARCH RATION MECH AN : 1.769
28. PHYS FLUIDS : 1.761
29. Journal of Crystal Growth: 1.707
30. RHEOL ACTA : 1.558
31. MECH MATER : 1.512
32. Int. J. Numer. Meth. Eng. 1.501
33. J. Acoust. Soc. AM: 1.482
34. INT APPL MECH+ : 1.427
35. INT J MULTIPHAS FLOW : 1.383
36. INT J SOLIDS STRUCT: 1.378
37. PHILOS MAG B : 1.343
38. Proc. Royal Soc. London, A: 1.325
39. ENG FRACT MECH : 1.299
40. J. Biomech. Eng-T ASME: 1.290
41. COMPUT METHOD APPL M : 1.263
42. INT J HEAT MASS TRAN : 1.220
43. Archiv. Comput. Meth. Eng. :1.182
44. PHILOS MAG : 1.167
45. COMPUT FLUIDS : 1.164
46. Geophysics: 1.087
47. Int. J. Eng. Sci. :1.065
48. J TURBUL : 1.062
49. J APPL MECH-T ASME : 1.012
50. INT J NONLINEAR MECH : 1.004
51. INT J HEAT FLUID FL : 0.988
52. THEOR COMP FLUID DYN : 0.957
53. EXP MECH : 0.954
54. INT J FRACTURE : 0.950
55. J ADHES SCI TECHNOL : 0.937
56. EUR J MECH B-FLUID : 0.930
57. MECH TIME-DEPEND MAT : 0.926
58. INT J MECH SCI : 0.906
59. WAVE MOTION : 0.902
60. Int. J. Fatigue: 0.874
61. EUR J MECH A-SOLID : 0.862
62. Quarterly Applied Math.:0.852
63. EXP FLUIDS : 0.851
64. INT J THERMOPHYS :0.846
65. CONTINUUM MECH THERM : 0.838
66. GEOPHYS ASTRO FLUID : 0.829
67. J SOUND VIB : 0.828
68. J Eng. Mater-T ASME: 0.819
69. THEOR APPL FRACT MEC : 0.806
70. STRUCT MULTIDISCIP O : 0.803
71. ENERG CONVERS MANAGE : 0.794
72. NONLINEAR DYNAM : 0.774
73. COMPUT MECH : 0.764
74. INT J NUMER ANAL MET : 0.758
75. J ENG Mech-ASCE: 0.743
76. KOREA-AUST RHEOL J : 0.727
77. ACTA MECH SINICA : 0.719
78. J COMPOS CONSTR : 0.712
79. OPEN SYST INF DYN : 0.702
80. Q J MECH APPL MATH : 0.701
81. J VIB ACOUST : 0.694
82. J THERM STRESSES : 0.692
83. Fatigue & Frac. Eng. Mater. Stru.: 0.673
84. FINITE ELEM ANAL DES : 0.620
85. FLUID DYN RES : 0.620
86. J NON-EQUIL THERMODY : 0.619
87. APPL MATH MODEL : 0.617
88. MULTIBODY SYST DYN : 0.610
89. MATH MECH SOLIDS : 0.609
90. NUMER HEAT TR B-FUND : 0.598
91. APPL THERM ENG: 0.596
92. J FLUID STRUCT : 0.590
93. INT J IMPACT ENG: 0.588
94. PROBABILIST ENG MECH : 0.554
95. ACTA MECH : 0.546
96. Zeitsch. fur angew. Math. und Phy. (ZAMP):0.546
97. J STRAIN ANAL ENG : 0.545
98. NUMER HEAT TR A-APPL: 0.524
99. MECH RES COMMUN : 0.522
100. ARCH APPL MECH : 0.514
101. INT J DAMAGE MECH : 0.514
102. J VIB CONTROL : 0.508
103. J ADHESION : 0.505
104. J WIND ENG IND AEROD : 0.500
105. MECH STRUCT MACH : 0.500
106. INT J COMPUT FLUID D : 0.485
107. INT J NONLINEAR SCI : 0.483
108. INT J NUMER METH FL : 0.476
109. Comm. in Num. Meth. in Eng.:0.476
110. INT COMMUN HEAT MASS: 0.441
111. J. of Applied Biomechanics: 0.438
112. J ELASTICITY : 0.433
113. Z. Angew Math Mech (ZAMM): 0.433
114. Quarterly Journal of Mathematics 0.408
115. Journal of Ship Research 0.388
116. Meccanica: 0.371
117. Int. J. of Num. Meth. for Heat & Fluid Flow 0.358
118. Int. J. of Appl. Electromagne. Mech. 0.348
119. Acta Mechanica Solida Sinica 0.341
120. Mech. Compos. Mater.: 0.331
121. Shock Waves: 0.312
122. Engineering Computation 0.295
123. CR Mecanique: 2.93
124. Dokl. Phys. : 0.291
125. Appl. Math. Mech-Engl
126. JSME Int. J. A-Solid Mech. Mater. Engin. 0.205
127. Engineering Failure Analysis 0.202
128. PMM-J. Appl. Math. Mech. : 0.200
129. JSME Int. J. --B -Fluids and Therm. Engin. 0.141
130. Sound Vib. : 0.137

THE MOST CITED SCIENTIFIC PAPERS IN SOLID AND COMPUTATIONAL MECHANICS

2006-04-24T12:29:00.000-07:00

Based on a survey of Web of Science, we compiled a list of papers that are
``THE MOST CITED SCIENTIFIC PAPERS IN SOLID AND COMPUTATIONAL MECHANICS PUBLISHED IN THE 20th CENTURY''.

The paper making the list must be: (1) in the areas of solid mechanics, mechanics of materials, or computational mechanics, and (2) it has at least 1000 citations.

First, since the citation is a dynamic process, both the entry and the order of this list may change from time to time. Second, this list may not be complete, if anyone finds a missing entry, please inform us, and we should include it immediately.
The survey is up to April 24, 2006, and we should keep it updated once every two months.

--------------------------------------------------------------------------

(1) ESHELBY JD,
The determination of the elastic field of an ellipsoidal inclusion, and related problems,
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL AND PHYSICAL SCIENCES 241 (1226): 376-396, 1957. Times Cited: 3781

(2) WILLIAMS ML
Mechanical properties of substances of high molecular weight .19. The temperature dependence of relaxation mechanism in amorphous polymers and other glass-forming liquids.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 77(14), 3701-3707, 1955. Times Cited: 3103

(3) GRIFFITH AA
The phenomena of rupture and flow in solids,
Philosophical Transactions of the Royal Society of London, Sereis A, 221:163-198, 1921. Times Cited: 2646

(4) MATTHEWS JW and BLAKESLEE AE
Defects and epitaxial multilayers: 1. Misfit dislocations,
JOURNAL OF CRYSTAL GROWTH 27 (DEC): 118-125, 1974. Times Cited 2426

(5) TAYLOR GI
Dispersion of soluble matter in solvent flowing slowly through a tube.
PROCEEDINGS OF ROYAL SOCIETY OF LONDON, A. 219, 187-203, 1953. Times Cited: 2232

(6) RICE JR
A path independent integral and approximate analysis of strain
concentration by notches and cracks,
JOURNAL OF APPLIED MECHANICS 35 (2): 379-386, 1968. Times Cited: 2032

(7) Taylor GI
Plastic strain in metals
JOURNAL OF THE INSTITUTE OF METALS 62: 307-324, 1938. Times Cited: 1753

(8) DUGDALE DS
Yielding of steel sheets containing slits,
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 8 (2): 100-104, 1960. Times Cited: 1688

(9) BIOT MA ,
Theory of propagation of elastic waves in a fluid-saturated porous solid. 1. Low-frequency range, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 28 (2): 168-178, 1956.
Times Cited: 1638

(10) MINDLIN RD,
Influence of rotatory inertia and shear on flexural motions of isotropic elastic plates,
JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME 18 (1): 31-38, 1951.
Times Cited: 1410

(11) Biot MA
General theory of three-dimensional consolidation
Source: JOURNAL OF APPLIED PHYSICS 12 (2): 155-164, FEB 1941. Times Cited: 1392

(12) ESHELBY JD,
The continuum theory of lattice defects,
SOLID STATE PHYSICS-ADVANCES IN RESEARCH AND APPLICATIONS 3: 79-144, 1956.
Times Cited: 1209

(13) RICE JR, ROSENGRE GF
Plane strain deformation near a crack tip in a power-law hardening material,
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 16 (1): 1-12, 1968. Times Cited: 1202

(14) HUTCHINSON JW,
Singular behavior at end of a tensile crack in a hardening material,
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 16 (1): 13-31, 1968. Times Cited: 1196

(15) MORI T, TANAKA K
Average stress in matrx and average elastic energy of materials with misfitting inclusions;
ACTA METALLURGICA 21 (5): 571-574, 1973. Times Cited: 1177

(16) Taylor GI
Th formation of emulsions in definable fields of flow
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL AND PHYSICAL SCIENCES 146 (A858): 0501-0523, OCT 1934. Times Cited: 1174

(17) BROOKS AN, HUGHES TJR
Streamline upwind Petrov-Galerkin formulations for convection dominated flows with particular emphasis on the incompressible Navier-Stokes equations,
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 32 (1-3): 199-259, 1982. Times Cited: 1090

(18) GURSON AL,
Continuum theory of ductile rupture by void nucleation and growth,
1. Yield criteria and flow rules for porous ductile media,
JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME 99 (1): 2-15, 1977. Times Cited: 1069

1993 Timoshenko Medal Lecture by John L. Lumley

2006-04-22T04:05:00.000-07:00

John L. Lumley

I am profoundly honored by the award of this medal. Awards like this are made, of course, not by faceless organizations, but by collections of individuals, voting in rooms which are no longer smoke-filled; it is particularly gratifying to find that so many of my colleagues think I am worthy of this honor. As Jan Achenbach remarked last year, we are of the sputnik generation, too young to have known Timoshenko, who, in fact, did have some connections with Cornell long before I came there. Although I have spent my life in fluid mechanics, I began by taking all the standard courses in solid mechanics: strength of materials, elasticity, plates and shells, buckling; in nearly every one there was a text by Timoshenko or a friend or relation, all admirably clear. I felt very grateful to him.

I would like to mention that the three ASME medal winners this year (Roger Arndt, David Crighton and I) were all together at Penn State in the Aerospace Engineering Department and the Garfield Thomas Water Tunnel, under the leadership of George Wislicenus about thirty years ago. Roger and I were on the faculty, and David came in the summers as a consultant. I think that says something about the vision and values that George used as he built his group.

I have heard a story about L. M. Milne-Thomson, whom we all know for his work on theoretical hydro- and aerodynamics. Many years ago he was asked to speak after dinner at a grand banquet in the Washington area. He may have been given an award; I am not sure. The banquet was attended by wives in elegant dresses, and there were naval officers of flag rank in class A uniforms. To everyone's surprise, he said that he wanted to give a technical lecture. After a short delay they found a tiny portable blackboard, and as he covered it with equations, he had two full admirals erasing for him in relays, tossing the eraser back and forth to each other over his head. I won't do that this evening.

Instead, I want to talk about becoming a scientist and being one, during the latter part of the twentieth century, in the United States. I realize that, when people reach my age, they think that anything they have to say is golden. I am reminded of Eric Walker, former president of Penn State. When he retired, he started writing a column in the local newspaper called "Now it's my turn". Many of us thought it had already been his turn for entirely too long, and his column was not too popular. I will try to spare you that syndrome as much as possible, but some of it is unavoidable. If the Medal Committee had any decency, they would not require a speech, and we would all be spared.

My father was an architectural engineer, and a do-it-yourself craftsman, car buff and spare-time artist. My earliest recollections are of being allowed to wash the spokes of the artillery wheels on our Hudson, while Dad polished the car with the chamois. We always had a car that was a little bit special, a little different. As we drove around Detroit, Dad would point out buildings that he had had a hand in designing or building. On Saturday mornings I remember being taken to completed buildings and building sites, and having the various flaws pointed out to me. Dad was a very demanding man; everything had to be just so. Ann Landers recently had a letter describing engineers as uncompromising, inflexible and perfectionist. That was certainly Dad. One of his friends said that Charlie was a wonderful guy, but he would hate like Hell to work for him. For years my mother talked about the dog house Dad built. It was large enough for a child to play in, with insulation and a shingled roof, and a baffle at the door to keep the cold wind out. It was a lot better built than many houses for people - certainly than the ones in Dade county in Florida. Dad never did manage to teach me how to do lettering and make arrowheads on drawings in a thoroughly professional manner, though God knows he tried. He also tried to get me always to make a complete set of drawings before I fabricated something; it never took - I always preferred to plan the project in my head, and make modifications as I went along; very unprofessional. Dad had ambiguous feelings about engineering, and from time to time thought he might have been happier as an architect. He once asked me if I was prepared to spend my life among these gray, inarticulate people. That's not entirely unfair, though I have grown rather fond of many of these people, who are only gray if you don't look beneath the surface. And there are not many, but enough poets and artists among us, so I am happy.

This is really how I got into engineering. I have always loved machinery, making things, building things. But I have spent my life as a research scientist, which is not quite the same thing. It seems that when I work on a problem, even a practical problem, I turn it into a research project; I chop it up finer and finer until there is nothing left but the fundamentals. In fact, half the theses I have supervised were experimental - a good experiment is a little closer to engineering; you usually have an opportunity to design some piece of equipment, and see it come into being. That, of course, is not quite the same as making it yourself. Evenings and weekends I restore old cars out in the barn - that satisfies the urge to make things. It also satisfies the craftsman-like desire to design in your head, with the materials and tools at hand, and modify as you go along. I get tired of too much calculation, too much precision, which I get enough of professionally. In addition, what I do professionally has a very delayed payoff - something of the order of twenty years or more. It is nice to do something that provides shorter-term gratification. It is also peaceful out in the barn.

There is less dichotomy than you might think, however, between what I do professionally and what I do evenings and weekends. I believe it was von Karman who said "There is nothing so practical as a good theory". I have always felt when constructing a very mathematical theory, that I was constructing something real and practical, to explain something physical, to make design possible. I have always been deeply offended by the attitude we meet so often, "it's just a theory", although I am certainly used to it.

More important, perhaps, I have always wanted to be involved with real things. That is, I have never wanted to abstract what I do too much, remove it too far from the real world, from the application. When I was in graduate school, it was rather nice to work on clean, neat problems that were somewhat removed from the real world. When I got my first job with George Wislicenus at Penn State, I was connected with the Garfield Thomas Water Tunnel, as well as with the Aerospace Engineering Department. The water tunnel is the world's largest high speed water tunnel, and is a part of the Applied Research Laboratory, that Penn State operates for the Naval Sea Systems Command. The Laboratory is responsible for various aspects of undersea warfare. At the Water Tunnel I was quickly immersed in the very practical problems arising from torpedoes and submarines: primarily various schemes for reduction of turbulent skin friction drag, and the many problems connected with testing in the water tunnel. At first I was a little appalled by the complex interdisciplinary problems. I had been unconsciously trained to be a bit disdainful of real problems; somehow, if you were concerned with real problems, it suggested that you didn't have the wit to find the fundamental problem underlying the real problem. It seemed that, to be socially acceptable in my circles, you never mentioned the real problem, but only the fundamental problem that you had abstracted from it. I discovered fairly fast that this was not such a straightforward matter, and that the business of reducing a real problem to a series of connected fundamental problems, all simple enough to resolve, without throwing out the baby with the bath water, was very challenging. Of course, in this reduction process you have to clip away everything that seems extraneous, hoping to be left with something that, while only a skeleton, still shares enough with the real problem to shed light on it. I think my colleagues often thought that I had pruned a bit too much, leaving a stunted stub that could not survive. However, even if they could no longer see the connection, I always saw the theoretical result as still directly connected to the real world. I also quickly came to see what a tremendously rich environment this was, how stimulating, how many problems there were to solve. I think it is a great mistake to get too far away from the applications; you dry up, you starve.

In the last few years I have managed to combine my hobby and my profession. When I was a relatively junior faculty member, I taught undergraduates. As I became more senior, however, I taught only graduate students, and for many years this was true. When I went to Cornell, I was told that I would have to teach undergraduates, but in fact I was never asked, and I never volunteered. Three years ago, however, I was made an offer I could not refuse, and I am now responsible for the undergraduate course in automotive engineering, with between fifty and one hundred students. This is one of our capstone design courses, and is a nice synthesis of much of what the kids have learned in their other courses. It is fun to teach, and I enjoy the undergraduates, although they still frighten me a bit. The young can be very judgmental and demanding. I think it helps to have raised some children. The first year I taught the course, my teaching evaluations were appalling - I hope the dean never sees them. I must say they were richly deserved. Now, however, the evaluations have substantially improved, and they no longer give me nightmares.

As I have gotten older, I have found that more and more I am a research administrator. I am sure I am not unique - this happens to all of us, but it is a bit sad. That is, I have less and less opportunity to do things myself. I am supervising others who are having all the fun. The world of science in which I live and work is structured differently now from the way it was when I was young. The world itself is changing, but of course it is also changing for me because I am getting older. The changes are also not uniform from country to country. In any event, at present, at my age, in this country, a successful scientist must have a large operation, which means a hand-full of contracts, students, post-docs, colleagues, visitors. This is a nice environment for the people working in it - I try to make it that way, recalling my earlier years. I certainly was very grateful for the environment that my thesis advisor created around us. Mostly that is simply a matter of collecting an interesting group of people, and letting them interact. I was an only child, and when I was little I became accustomed to playing by myself. Probably because of that, what attracted me to science was the pleasure of working alone at a problem uninterruptedly, following thoughts to their conclusions, trying various possibilities. I now recognize that that is not always an efficient way to work - it sometimes makes more sense to break off, and sleep on a problem, or do something unrelated, or go to the library and read something that someone else has said on the subject. That was something I never wanted to do when I was young - I didn't care what someone else had said - I wanted to do it myself. In any event, this lovely environment for everybody else is not really a nice environment for me. Whether it is desirable or not, uninterrupted work is rarely possible for me. I function in the interrupt mode, which I understand is the norm for managers. In addition, I do virtually nothing myself, but must act collaboratively with others, and at second hand. This makes me feel somewhat like a child who is forced to share his toys.

Gertrude Stein compared politicians to garbage collectors; they do necessary, but not very exciting, things that keep the place running, and are not really noticed until the system breaks down and the garbage is not collected. Administration is a lot like that, even research administration. A lot of what I do these days is the moral equivalent of garbage collection.

When I came to Cornell, of course I no longer had a connection with the water tunnel and its sophisticated but practical problems. At Cornell, I have found a certain satisfaction in being an expert witness and consultant. The problems that I solve in this capacity are reminiscent of the problems that I enjoyed resolving when I was younger. They are practical problems, usually complex and interdisciplinary, which must be broken up and abstracted to be resolved. This process involves some technology transfer, since I am often applying fundamental things that my research has taught me over the years to industrial or environmental problems.

Sometimes it is like detective work. Let me tell you about something I worked on last year, that will illustrate how a complex, interdisciplinary practical problem can lead to fundamental problems. This is in the area of atmospheric turbulence, in which I worked for some years at Penn State. Some of the material may be unfamiliar, but I think you will find the logical chain interesting. My client was a sheep farmer whose sheep seemed to be dying as a result of emissions of sulfur dioxide and hydrogen sulfide from a heavy water plant. Both sulfur dioxide and hydrogen sulfide are toxic in sufficiently high concentrations. The farmer was just a kilometer and a half from the plant, which is very close, but any normal calculations suggested that his sheep were receiving concentrations at a level considered completely safe. In addition, monitoring stations placed near his farm indicated low concentrations. I must explain how Hydrogen sulfide and sulfur dioxide happened to be emitted. Hydrogen sulfide is used in the process of making heavy water, and once a year the towers in which the heavy water is made have to be cleaned. After as much hydrogen sulfide as possible has been removed from the towers, the majority of the remainder is burned on a flare stack and converted to sulfur dioxide. The plant was right on the edge of one of the great lakes, and the stack was close to the water. After several false starts, we finally realized that the on-shore breeze from the lake, during the spring and summer, was stably stratified, and thus not turbulent, from traveling over the cooler lake water for hundreds of kilometers. The top of the stack was in this stably stratified air. Thus, the stack plume did not disperse. The cool, stable air, when it started over the warmer land, began to grow an internal turbulent boundary layer, and when this reached the height of the stack plume, the plume was sucked into the first downgoing eddy, and taken to the surface. The distances were about right so that the place where this happened was right over my client's farm, and the first descending eddy was probably caused by his cool, insulated farm buildings. His sheep were thus getting the stack plume at nearly full strength. The plume, of course, did not descend on the monitoring station. The matter was complicated by the fact that the sulfur dioxide was considerably heavier than air, and could lie on the ground in hollows among the vegetation, where the sheep would be immersed in it.

This general situation is called shoreline fumigation, and is well-known to meteorologists. However, they are only familiar with the average effects. The phenomenon of the descent of the instantaneous plume to ground level, with its associated high instantaneous concentrations, has not been measured. One of my colleagues has now submitted a proposal for laboratory measurements of instantaneous concentrations in this situation. In addition, the pooling of the sulfur dioxide at ground level, and the probability of its remaining for various periods, was a nice little fundamental problem that was fun to solve.

Everything has its down side, and I must admit I don't much like being questioned in hearings. In addition, this was all part of an environmental impact hearing in connection with a request for license renewal for the heavy water plant. When it became evident that my client had a case that would stand up, the request for license renewal was withdrawn. As a result, the outcome is moot. Also, although I work hard at communicating my results, I sometimes suspect that my clients find my name and credentials more useful to them than my findings. That's all right - at least I had fun.

Well, I hope I have kept you awake. Let me thank you again for this wonderful honor you have bestowed on me.

A Virtual Tour of the 1906 Great Earthquake in Google Earth

2006-04-18T19:39:00.000-07:00

The California earthquake of April 18, 1906 (one century ago today) ranks as one of the most significant earthquakes of all time. Today, its importance comes more from the wealth of scientific knowledge derived from it than from its sheer size --it marked the dawn of modern science of earthquakes.

U.S. Geological Survey (USGS) recently provides a virtual tour utilizing the geographic interactive software Google Earth to explain the scientific, engineering, and human dimensions of this earthquake. This virtual tour can help you visualize and understand the causes and effects of this and future earthquakes.

Enjoy this virtual tour to explore how Google Earth (and other new softwares...) can facilitate and improve the way we teach and conduct research.

Organic LED could replace light bulb?

2006-04-17T06:56:00.000-07:00

Lighting accounts for about 22% of the electricity consumed in buildings in the United States, and 40% of that amount is eaten up by inefficient incandescent light bulbs. The search for economical light sources has been a hot topic.

Recently, scientists have made important progress towards making white organic light-emitting diodes (OLEDs) commercially viable as light source. As reported in a latest Nature article, even at an early stage of development this new source is up to 75% more fficient than today's incandescent sources at similar brightnesses. The traditional light bulb's days could be numbered.

Read media report here.

A new wiki is set up to solve the Millennium Problems in Mathematics

2006-04-16T04:24:00.000-07:00

This entry in Slashdot links to the new wiki, from which one can at least learn what these problems are, as well as their prize tags. The 139 comments in Slashdot once again show the issues concerning any wikiscience project.

2001 Timoshenko Medal Lecture by Ted Belytschko

2006-04-15T20:45:00.000-07:00

Ted Belytschko, November 13, 2001, New York

Well I have been sitting in the audience of Applied Mechanics dinners for more than 30 years now, never even dreaming that I would get the Timoshenko medal. I have enjoyed many of the talks, and heard many nuggets of wisdom to guide me in research and life. I still vividly remember one of the first talks I heard by Den Hartog- in those days every Timoshenko lecturer could still start with a reminiscence of their contact with Timoshenko. Den Hartog had worked for Timoshenko one summer, and when he wrote his study up as a report, Timoshenko told him to submit it for publication. Den Hartog responded that he did not think that this work was something the world was waiting for. Timoshenko replied-"How many publications that have appeared in the literature do you think the world was waiting for?" One outcome was that I proceeded to publish too many papers, but it is interesting that many of the papers I did not think much of had some impact, whereas many that I liked had no impact .

In preparing this talk, I noticed that many of the talks were autobiographical. But I quickly decided not to make mine autobiographical because I still remember that when I was program chairman, a very witty and brilliant Timoshenko medallist chose his autobiography as the topic. He was only eighteen by 10 PM, and I was at the edge of my chair because I was Program Chairman and the union crew that was waiting at the doors of the banquet hall to clean up.

So I will not give an autobiography, but I would like to say a few words about my teachers. The most important teacher in any research career is the Ph.D. advisor. My advisor was Phil Hodge, who many of you know and who was also advisor of Carl Herakovich, a former member of the Executive Committee who is sitting at the center table. Phil came from Brown, trained by William Prager, and he taught us many things: the importance of clarity and conciseness, personal integrity, and the joys of a career in research and teaching.

Phil also gave us some maxims that you might find useful. One was: "Any research worth doing is worth doing well." The other, which I have found even more useful, went something like this: "Academic paperwork has to be done, but it is usually not worth doing well."

My other mentor was Ernie Masur, who was Chair in my first position at the University of Illinois at Chicago. Ernie was quite different from Phil-whereas Phil trudged to the computer center every day with a box of cards for his daily run- in those days you were a computer jock if your computer cards filled one box, a superjock if it required two or more boxes -Ernie disdained to even type, saying that gentlemen did not type. But Ernie had impeccable taste and a terrific nose for what he called "substance", and he taught me to recognize the substance from the chaff. He also had a great sense of humor, though wit, like principles, can’t be taught

A Timoshenko talk I really enjoyed was Roshko's talk "Think Small." There were many precepts in his talk that I found very appealing, so I have decided to take a similar vein but call it "Think Big Persistently." Now you might think I am contradicting him, but some of the things I will say echo what he said.

I will address only two facets of thinking big persistently-what it means for young people, and what it means for our society, the Applied Mechanics Division.

First let me address the Applied Mechanics Division. Over the thirty years that I have been associated with this Division, the research of this group has continued to flower: the impact of this Division on the applied and theoretical issues of engineering and science has been simply amazing. Fracture mechanics, the theory of plasticity (which really underlies almost all rational nonlinear material models), micromechanics, composites, the finite element method have either originated here or owe a large part of their development to this Division. Yet, during this time, funding from NSF, which is still the best place for research support and supports many pure and applied fields very generously, has almost shrunk to zero.

This is astounding when one considers the impact of this Division on basic knowledge, basic knowledge that is not only intellectually beautiful, but has had tremendous impact on our society. This one of the most talented groups in analytic thinking in the world and the closed form solutions that have been produced by this group have provided the basic understanding of a host of important phenomena. I might add that although I am a computational mechanician, I often say that: “A good closed form solution is worth a thousand of computations."

Now it is difficult to ascertain to what to exactly ascribe this decline, but I have long felt that it is not strictly due to external forces. I believe it stems from our lack of self knowledge, our lack of identity and our reluctance to sell ourselves. Many disciplines, like computer science, have actually hired lobbyists to plead their cause, but as a Division, we almost never talk to the upper echelons of NSF or Congressional staffers. There have been a few attempts at this, but they always seem to wane, and that is why I have added that we must think big persistently-the benefits of interactions do not come overnight

Another source of our difficulties is our fuzzy self-identity. For many years, this Division has attempted to represent fields that were no longer a part of it- the fluid mechanicians have departed for the American Physical Society, but we still included fluids, and most dynamicists are in other places, but we still pretend that it is part of our Division. Perhaps even the name of our division is no longer appropriate. For one thing, the name is not appealing to younger people-most young people starting careers in research and teaching want a more attractive name, they don't want to be confused with those who fix their cars. Furthermore, most of us are not really engineers-much of our work is indistinguishable from physics or from materials science. I daresay the contributions of some members of the Applied Mechanics Division, such as Jim Rice and John Hutchinson, rank with the most important in materials science. So maybe we should look at another name-it was very beneficial for soils engineers, who changed their name to geotechnical engineering, and have much improved their image with the public.

What should such a name be? I have asked a number of people. Some would not even give it an attempt, because they consider it sacrilegious. Lalit Anand, a former member of the Executive Committee, proposed “Solid and Mechanical Engineering and Sciences.” He suggested we would then go by the acronym SMEC. My preference is "Science and Engineering of Solids" -SES. I think it is high time we recognize that we are scientist as well as engineers, and that we get a name that accurately reflects what we do and what we have done!

But more important, the Executive Committee and its past members should be in constant contact with people at Congressional staffers, NSF and other funding agencies. There are 10,000 of us in ASME and more in ASCE, and I think we should have a strong voice. We have to let them know what we do, why it is important, and what we can do for the country. This can not be a one-shot effort, it needs to be done persistently. (for example, Mathematics has just won a commitment for a fourfold increase in funding through such long-term efforts)

My second theme pertains to young people, to whom I would like to give some advice based on my past successes and mistakes. To think big is to look for important problems at the cutting edge. Too many young researchers choose their topics by reading a paper and seeing how they can extend it- that is not how the important problems are found. You have to talk with many people, read both the literature of your disciplines and other fields, and identify the emerging fields and important problems. I fortunately stumbled into nonlinear finite elements through my consulting work early in my career-I wrote a crash code in 1971 when a visionary in DOT initiated a research program by selling the idea that crash testing could be replaced by computer simulation. Well at that time, computers were so slow that even a 500 element simulation (500,000 are customarily used today) cost more than a test, so the program was quickly shelved. But it gave me the opportunity to do some work in a new area that had considerable impact.

To highlight the importance of working on new problems, I quote Arno Penzien, the Noble Prize winner who discovered the background radiation that underpins the big bang theory: “ there are two types of scientists: 2% discover new things and blaze new frontiers, the other 98% fix up their mistakes; the accolades go to the former.”

It is also crucial for the success of this Division that we nurture our young researchers- our future obviously lies with them. In this, I think that we must de-emphasize the role of money in our promotion criteria. We have now reached the point where in many schools, the volume of money supersedes all other factors in a professor’s promotions and recognition. This is really quite absurd, since a university does not exist to make money- our purpose is to teach and do research, and money is only a means to that end. But in many places, right at the top of your annual report is your dollars spent. Everyone seems to have become obsessed with the U.S. New and World Report ratings, in which money plays a dominant role. If this trend continues, I can see two young assistant professor talking one day and wondering: "What is the fuss over Einstein all about?- I hear he never brought in 100k per year.”

So I think we ought to persistently remind our administrators that our goals are not to bring in money. Administrators have incorporated indirect funds into operating budgets, so they are becoming addicted to large research fund flows. It will be a big job to bring this to an end, but if we can think big and persistently, we can at least moderate this.

There are tremendous opportunities for us in emerging fields such as micromechanics, nanomechanics, cellular mechanics, biomechanics, computer simulation, and many that are only barely visible on the horizon today. But to enjoy these, we must do the things that need to be done persistently.

To conclude, I would like to thank my family, my wife Gail and my children Peter, Nicole, and Justine; my colleagues at Northwestern in the field of mechanics, Wing Kam Liu, Brian Moran, Jan Achenbach, Cate Brinson, Zdenek Bazant, Jian Cao, Isaac Daniel, and John Rudnicki (we have the best group in the world, and their collaboration, collegiality and competitiveness have helped me immensely), my students and post-docs, and my professional colleagues, particularly Tom Hughes and Tinsley Oden, who were so instrumental in my winning this award.

Nanogenerators created by a team led by Zhonglin Wang

2006-04-13T18:02:00.000-07:00

1989 Timoshenko Medal Lecture by Bernard Budiansky

2006-04-08T04:05:00.000-07:00

Professor Bernard Budiansky delivered this lecture at the Applied Mechanics Dinner of the 1989 Winter Annual Meeting of ASME, in San Francisco, California. He died in 1999, and his colleagues at Harvard University have published a memorial minute.

Reflections
Bernard Budiansky

Many thanks for honoring me with the Timoshenko Medal. Forty-five years ago, fresh out of college with a bachelor’s degree in civil engineering, I started my first job at Langley Field, Virginia, with the National Advisory Committee for Aeronautics, and my very first assignment was to learn about buckling of plates from Timoshenko’s famous book on the theory of elastic stability. Timoshenko’s extraordinary influence on research and education in applied mechanics all over the world, and his central role in this country, needs no reiteration. Like so many others, I was seduced by his book into a life-long infatuation with buckling problems, and so to receive this award bearing his name from my fellow applied mechanikers is very heart-warming, and I am very grateful.

On occasions like this, it is traditional for the speaker to grapple with cosmic issues of research, educations, scholarship and the like, even though he would feel much more comfortable giving a technical lecture. One distinguished colleague managed to rattle me thoroughly by saying – I think mischievously – that he looked forward to my “words of inspiration”; on the other hand, John Hutchinson simply suggested that I keep it short.

Not only will I follow John’s advice, I will also avoid major matters of science and technology, because I neither have any profundities to peddle, not do I wish to contribute any new cliché’s or buzzwords to these subjects. The present supply is quite adequate. I have to admit that I was really impressed the first time I heard the phrase “the cutting edge of technology” (even though the imagery did no quite match that of Tom Lehrer’s immortal line about “sliding down the razor blade of life”) but after several hundred repetitions, the effect has grown dull. Words and phrases invented inside the Beltway do spread like wildfire. One popular Washington proverb I can do without is: “If it ain’t broke, don’t fix it.” This is a perfect prescription for the technological stagnation that is often deplored in the next breath. In the last few years, we have been deluged with “initiatives” – Strategic Defense Initiative (SDI), Universities Research Initiative (URI), Accelerated Research Initiative (ARI), and so on. My current favorite is the recently announced BNI – Bold New Initiative – which sounds exciting, but I have forgotten what it’s for. Heavy phrases like technological innovation, manufacturing productivity, international competitiveness, and environmental disaster are on everybody’s lips. I certainly do not wish to demean either the importance of the issues they represent, or the seriousness with which the problems are being confronted. However, I am sure you will be relieved to learn that these topics are beyond the scope of the present talk.

What I will do is reflect a bit about applied mechanics and applied mechanikers. At the same time, I will try to avoid excessive introspection, which I consider to be a dangerous practice that can lead to a morbid preoccupation with the meaning of life. Fortunately, it seems to me that most of us in applied mechanics do enjoy a fairly un-self-conscious approach to our work, relatively free of subjective inner contemplation. To varying degrees, we simply love to do research in our fields, we accept the frustrations, false starts, and dead ends that go with the territory, and do not make a habit of either melancholy self-doubt or manic self-adulation. And so, to those who assert that the unexamined life is not worth living, I say, speak for yourselves, and let me get back to work!

But if research in applied mechanics is such a happy enterprise, why are we occasionally afflicted with the Rodney Dangerfield syndrome, namely: “We don’t get any respect!”? We share a monumental intellectual legacy of knowledge and achievement, and our contributions to many branches of engineering and applied sciences are central, vital, and growing. And yet, the visibility and recognition of applied mechanics as a coherent discipline has been diminishing, not only in the eyes of the general public, where it has always been negligible, but within the scientific and technical establishments as well. Starting at the top, applied mechanics as a field of learning and research is surely terra incognita to the President of the United States, his cabinet, most members of Congress, the CEO’s of the Fortune 500, all but a handful of university presidents, and about a quarter of a billion other Americans, including even the Vice-President. University departments or division tagged with the applied mechanics name seem to be in a process of extinction. With some exceptions, governmental funding agencies tend not to assign the applied mechanics label to the research they support. Neither the National Academy of Engineering nor the National Academy of Sciences nor the American Association for the Advancement of Science contains a section in applied mechanics. I have yet to see the words “applied mechanics” in the science pages of any newspaper or newsmagazine, and I suspect that they have rarely, if ever, appeared in general science publications like Science or Nature or Scientific American. But we do exist! We are like members of a closely knit secret society, with clandestine cells in mechanical, civil, chemical, and aerospace engineering, in geophysics, in materials science, in biotechnology – but we’re quite ready and willing to have our cover blown!

There are two obvious reasons for this lack of visibility, one sublime and one ridiculous. Our very success in promulgating the role of applied mechanics within such a large number and variety of fields has led to the seamless integration of substantial parts of applied mechanics into the various fields I mentioned. This, of course, is very welcome. But as a natural consequence, subsequent research in such an incorporated segment of applied mechanics tends to assume the identity of its host. The absurd reason for our lack of status is that we still don’t know what to call ourselves! Can it be that this is the crux of the problem? We are not the only group whose activity cuts broadly across traditional disciplinary boundaries, but mathematicians, engineers, physicists, biologists, and computer scientists proudly retain their identities, no matter how scattered and diverse their working environments, and, of course, their titles provoke instant recognition. But what are we? In informal conversation, “applied mechaniker” is all right, but is clearly too whimsical and slang-ey for general acceptance. Some years ago, Norman Goodier urged the adoption of the appellation “applied mechanicist” but this never really took hold, and “applied mechanician” doesn’t seem to make it either.

Well, so what? Is this a true identity crisis, or just an annoying pinprick to our collective ego? After all, we do respond with acceptable answers when our neighbors ask us what we do for a living, or when we have to fill in the blanks labeled “occupation” on our income-tax forms or passport application. I suppose most of us say “engineers”, some say “mathematician”, others (like Irwin Corey) simply say “professor”, or “educator”, or “geophysicist”, or something else as respectable. The fact is, we all do have at least one profession we can honestly claim besides our beloved applied mechanics. I am reminded of Josephine Baker’s song “J’ai deux amours, mon pays et Paris”, but the analogy is not apt, because everybody’s heard of Paris! Furthermore, most of us certainly do not want to sever our professional allegiances to the traditional fields. The engineering profession, in particular, has its own serious problems that may be worthy of our attention. And since applied mechanics should be truly interdisciplinary, might not intellectual isolation and sterility be an unhappy consequence of the greater autonomy that would inevitably flow from increased visibility for applied mechanics? And therefore, shouldn’t we leave well-enough alone? Finally, we obviously do enjoy substantial communal ties. Here we are in the Applied Mechanics Division of the ASME, there is a parallel Engineering Mechanics Division of ASCE, we have a National Congress of Applied Mechanics and an International Congress every four years, and we have umpteen journals as outlets for our research publications. So why worry?

I have almost persuaded myself to adopt the Panglossian view that everything has happened for the best – but not quite. First, and maybe foremost, greater visibility would obviously attract more talented young people to applied mechanics, and I know that most of you share my belief that this is very much needed. Next, greater autonomy for groups in applied mechanics could enhance interfield communication, and spark the effective spread of applied mechanics into new areas. (The models for this are the spectacular rise of biomechanics in the last few decades, and the vigorous growth of mechanics in materials science and geophysics.) There’s more: applied mechanics and applied mathematics have gone hand in hand for a long time, with applied mechanics people taking major responsibility for university instruction in applied math. Weaken applied mechanics and you weaken applied mathematics, and this has been happening. In connection with applied math, let me say a word about computing; our applied mechanics community has led, and continues to lead, the exploitation of computers in scientific and technological research. As a long-time addict, I am enthusiastically pro-computer, and I never used to take very seriously the gloomy prediction of some of my uncontaminated colleagues, who deplored the inanities of massive, mindless computations as substitutes for elegant classical analysis, and foresaw the loss of analytical skills that would be induced by excessive reliance on computers. But now I believe that the balance has finally tipped, that applied mathematics in the classical sense, needs rescuing and that strengthening applied mechanics may be the best way to do it. Finally, we need the extra power and freedom that would flow from greater visibility and prestige in order to secure the right to do what I would call pure applied mechanics. Such research is intended to nourish the heart and soul of applied mechanics, and is not particularly meant to be “useful” in any prosaic sense. Its virtues – something funding agencies would, of course, have to judge – would be measured on the basis of depth, beauty, and truth, the same graces that characterize and justify good pure mathematics. Incidentally, I have no patience with the widespread myth that pure math, done without applications in mind inevitably turns out to be “useful”; sometimes it does, but more often, it doesn’t. However, the phony promise of ultimate utility is not necessary to justify support of pure math, and I demand equal treatment for a certain amount of pure applied mechanics!

So if we agree that we should burst the bonds of anonymity, perhaps we should begin by coming to grips with the question of our job description. I could live with either “applied mechanicist” or “applied mechanician”. Why not boldly start using one or the other at every opportunity, and let the better one survive! Then – let’s lobby scientific and technical societies, honorary or otherwise, that have not yet seen the light, to establish applied mechanics divisions! In universities, reverse the slide into oblivion and recommend that establishment of applied mechanics committees across standard departmental lines, maybe empowered to grant degrees as well as give courses! Preach to funding agencies about the merits of interdisciplinary sections of applied mechanics! Give interview, or write popular articles, about applied mechanics and its practitioners! Run for Congress!

Well, enough agitation, which does not fall within my area of expertise, anyhow. To conclude these reflections, I would like to flip quickly though some verbal snapshots of a few of the people who have enriched my professional life. I had a remarkable trio of bosses in my first job at the Structures Research Division of NACA in 1944; Pai-Chuan Hu, a fresh Ph.D. in Engineering Mechanics from the University of Michigan, whose knowledge and intellect were awesome; Sam Batdorf, a renegade physicist, whose insightful way of thinking about problems in applied mechanics has been an enduring inspiration; and the big boss, the Chief of Structures Gene Lundquist, a great pioneer of structures research, whose legacy as a research leader has been enduring. It was an exciting time at NACA, in those pre-space days of aeronautical research, and my experience there has left me fiercely supportive of scientific civil servants, who are at least as smart and hard-working as those in the private sector, but often are slandered by invidious comparisons. I was lucky to meet and even interact with some famous people at NACA outside my field of structures, like Ed Garrick, Carl Kaplan, and the great aerodynamicists Robert T. Jones and Adolph Busemann, who had independently conceived of swept wings for high-speed flight – Jones in America, Busemann in Germany. Jones told me how to calculate the lift on a swept wing, so that I could go on to study its aeroelasticity. Busemann got sufficiently interested in plasticity to join Lyell Sanders, John Hedgepeth and me in many happy hours of exploration of 6-dimensional stress space. Busemann had a marvelous, infectious technical vocabulary in English; an eavesdropper would have heard us earnestly discussing Humpty-Dumpties, meaning hyperspheres; stalactites, meaning hypervectors; and stalagmites, vectors pointing the other way! When I went to Brown University for graduate study in applied math, what an extraordinary group of professors I had: Prager, Drucker, Carrier, Lee, Handelman, Greenberg, Diaz – all of whom taught me much more than simply the material in their courses. During those early post-war years, Brown attracted a fantastic international brigade of graduate students: among my special buddies were Frithiof Niordsen, Carl Pearson, Jean Kestens, Pei-ping Chen, and Hirsch Cohen – respectively, from Stockholm, Vancouver, Brussels, Peking and Milwaukee. (As you see, I am name-dropping shamelessly.) It has become a cliché that one learns as much from fellow students in graduate school as from faculty – and was this ever true in my case! As I look back over my life in applied mechanics during the decades that followed, I realize that I always think first of people rather than problems. (If this be introspection, make the most of it.) I suppose I love applied mechanikers as well as applied mechanics, and I had better start rationing my sentimental recollections. But I particularly want to mention Eli Sternberg, sadly gone now, our pre-eminent elastician, whose extraordinary charm, wit, and intelligence brightened and blessed us all, and whose friendship I cherished for over forty years; and the incomparable Max Krook, astrophysicist, applied mathematician, and certainly applied mechaniker, who actually knew everything. I have been enormously influenced, instructed and encouraged by Warner Koiter, the sage of Delft; and now, for over a decade, by Tony Evans, the ceramics guru of the western world. A little more introspection, despite by vow: there are many styles of research, none intrinsically superior, but I have to be able to exchange ideas freely, and talk things out, face-to-face with others. Recently, I was stopped by a camera crew doing snap interviews on campus, and was asked what I liked best about Harvard. Without any chance to reflect, I popped out the answer: colleagues. And so it is, even after reflection. How very fortunate I have been to enjoy the company of such a splendid group of kindred spirits in applied mechanics. I owe them more than they would be willing to believe, and here’s who they are: George Carrier and Howard Emmons, recently inducted into the ranks of the emeritus professors; and the remaining hardy band of applied mechanikers Fred Abernathy, John Hutchinson, Dick Kronauer, Tom McMahon, Jim Rice, Lyell Sanders, and Howard Stone. We will do our best to keep and promulgate the faith, and I hope you will too! Thank you.

USNC/TAM Report on Research Fluid Dynamics

2006-04-05T10:46:00.000-07:00

Carl Herakovich, the secretary of the US National Committee on Theoretical and Applied Mechanics (USNC/TAM), has posted the following entry in the Applied Mechanics Google Group today:

The USNC/TAM has just released a report by a Subcommittee on Research Directions in Mechanics, entitled Research in Fluid Dynamics: Meeting National Needs.

1985 Timoshenko Medal Lecture by Eli Sternberg

2006-04-01T01:15:00.000-08:00

Rumination of a Reclusive Elastician

By Eli Sternberg

Delivered at the Applied Mechanics Dinner of the 1985 Annual ASME Meeting in Miami Beach, Florida

Ladies and Gentlemen: As you know, medals - much like arthritis - are a common symptom of advancing years. Be this as it may, I am grateful for the recognition implied by this award.

Every medal has a proverbial reverse side. The reverse side of the Timoshenko Medal is the requirement that the recipient must make a speech. In view of my lifelong allergy to after-dinner speeches, the thought of having to give one has been rather unsettling. To make matters worse, I was asked over two months ago to submit a title for my talk.

Since a technical topic seemed inappropriate for the occasion, I tried hard to think of a suitably broad and vacuous subject: something with a sexy title, like "Applied Mechanics - Past, Present, and Future." I abandoned this idea, first, because I always feel a little uneasy in making pronouncements about the future of anything and, second, because I am not sure I know what is meant by "Applied Mechanics".

I had been in a similar quandary as to the meaning of "Applied Mathematics" until a good many years ago, when Lester Ford, who was then chairman of the mathematics department at the Illinois Institute of Technology, called me into his office to show me a letter he had just received from an inmate of Alcatraz Prison. It read: "Dear Professor Ford, I am serving a life sentence at Alcatraz and am studying calculus on my own. I don't know how to solve Problem No. 3 on p. 275 of the calculus book by Granville, Smith, and Longley. Can you help me?" I allowed that this was an amusing letter, at which point Professor Ford handed me a copy of the book. Problem No. 3 on p. 275 started with the sentence: "A tunnel is to be drilled." If this isn't Applied Mathematics, what is?

Anyway, under duress to supply a title for this talk well in advance, I attempted to concoct one sufficiently noncommittal to permit me to hold forth on just about anything that might eventually come to my mind. I think you will agree that I succeeded admirably in choosing such a title.

Having spent all of my professional life in mechanics at academia, I finally decided to take advantage of a predominantly academic, captive audience and dwell on certain developments that have detracted from my favorite environment. Although some of what I intend to say applies to the contemporary academic scene in general, a more communicative heading for my remarks this evening might be: "Mechanics - an Apprehensive View from the Ivory Tower."

To begin with, there is the undeniable observation that mechanics, as an independent academic discipline, has suffered worrisome setbacks during the past twenty years or so. This fact is reflected in the demise of several mechanics departments at major American universities, the erosion of existing mechanics faculties, and the decline of the student population in mechanics. There are various and diverse reasons for this trend. Among them is the not uncommon perception of mechanics as an essentially stagnant field. After all, some of my physicist friends still regard the discovery of Hooke's law in the seventeenth century as the last noteworthy event in the history of the theory of elasticity.

Another, related circumstance is the need to cultivate important emerging disciplines. Given the financial limitations on university budget, as well as the inevitable time constraints on academic curricula, engineering schools are apt to look for compensatory cutbacks in traditional activities and at times see in mechanics a natural victim of such efforts toward modernization.

As far as the furtherance of computer science is concerned - and here I speak out of the richest store of ignorance conceivable - no one would earnestly question the enormous value of computing to applied mechanics and indeed to all of applied science. Yet computing without a proper theoretical background can be hazardous to the public health. Thus there are grounds to worry about the rising traffic in finite element codes for stress analysis, which are often secret codes (in the sense that their theoretical basis remains a closely guarded secret) and the authors of which are occasionally uninhibited by a more than cursory acquaintance with the theory governing the problems they purport to solve.

For this reason alone a serious background in mechanics is hardly a luxury safely to be done away with. But mechanics need not rely on such a tenuous defense. Not only has it provided unparalleled inspiration for far-reaching scientific achievements in the past, it has made impressive strides in more recent times that have illuminated its foundations, enlarged its scope, and encompassed new technological applications.

Even elasticity theory, which (to my unbiased mind) is the very model of a mathematically sound and physically successful theory – though declared dead in some premature obituaries, has not stood idle. Nor is it likely to become obsolete in the future. I am rather confident that the theory of elasticity will be around and useful long after some of the more glamorous additions to engineering curricula have joined the company of fading fads and discarded fashions.

By and large teaching has been one of my favorite preoccupations over the years. In fact, trying to make things clear, whether in lecturing or in writing, is an ultimately rewarding, if often painful, obsession of mine. And, incidentally, whenever I have particular trouble in explaining something to others, I usually find that it is not clear to me either.

My enthusiasm for teaching has been somewhat dampened by a no longer novel phenomenon that has, in my view, contaminated the academic teaching atmosphere. I am alluding to the teaching-quality surveys conducted by students, which are firmly entrenched at most universities and enjoy a blissful immunity from criticism: any faculty member venturing to question the merits of this ritual can count on having his own motives questioned in turn. Now this is hardly an issue to become exercised about, but it is cause for some legitimate concern. Let me start with a few truisms.

First, these surveys evidently serve a useful purpose: for example, in making teachers aware of distracting mannerism and bad habits, like speaking too fast, writing illegibly on the blackboard, or standing in front of what has been written.

Next, as the husband of a psychologist, I know that polls of this kind are conducive to the mental health of students in enabling them to vent their resentment against a teacher by taking anonymous potshots at him or her. I still remember from my own undergraduate days being handed a questionnaire at the end of an explosively dull course. It called for the usual ratings of the instructor for "mastery of subject," "clarity of presentation," "fairness," and so on. In addition, it asked for an overall grade for his performance: A, B, C, etc. In a fit of mischievous inspiration, I gave the man an "Incomplete." I doubt if he enjoyed the joke nearly as much as I did at the time.

Lastly, nobody can prevent students from carrying out and publicizing the results of such surveys.

My misgivings pertain to the official sanctioning of this sort of enterprise by university administrations and the weight assigned to its outcome in connection with faculty promotions. At my own university the annual teaching-quality evaluation is undertaken with the cooperation of the Registrar and reported on in a publication funded by the Office of the Vice-President for Student Affairs.

Why misgivings? Because such evaluations tend to inflate the importance of the most superficial aspects of teaching; because they invite a popularity contest among the faculty that may favor glib and facile efforts over more demanding expositions in depth. Further, it seems to me that students - even graduate students -may not be in a position to assess the true competence of an instructor or the permanent value of the material presented. Perhaps the most memorable teacher I ever had was a notoriously poor lecturer, and I failed to appreciate fully the influence of my exposure to him until later in life.

I might add my surmise that there is little of substance that can be taught about teaching at the university level and - Schools of Education notwithstanding - even less on a level of generality that divorces teaching from the subject to be taught.

Along with teaching, most universities place considerable emphasis on scholarly accomplishments of their faculty. I am glad to say that the old chestnut about an inherent antagonism between teaching and research has largely been put to rest nowadays.

But the dangers arising from an indiscriminate reliance on the number of publications as a criterion for academic advancement are too self-evident to be belabored. One way of coping with the perennial academic dilemma of "Publish or Perish!" is to publish perishables. There is a natural temptation, especially among younger people, to pad one's list of publications with minor spin-offs of earlier work, and an understandable reluctance to invest the time needed to learn something new.

Such pressures are in part responsible for the current avalanche of papers on mechanics, the number of authors of which threatens to exceed the number of their readers. Moreover, this state of affairs has led to a proliferation of ever more specialized journals catering to mechanics of one kind or another: any day now I expect to receive notice of a new International Journal of Shear Stresses.

Let me move on to some troubling trends in the role played by sponsored research at our universities. It is a fact - a regrettable fact, but a fact of life just the same - that American universities depend on sponsored research for their survival. As a consequence professors are expected to cover a substantial portion of their salaries through outside support. This, in turn, compels them to spend an appreciable portion of their time on entrepreneurial chores, such as the composition of seductive proposals - hardly the most appealing genre of creative writing.

More disturbing is the spreading practice of making new academic appointments explicitly contingent upon the faculty member's ability to attract a specified percentage of outside support. This practice is particularly burdensome for younger faculty, and especially so in a field such as mechanics, where funding is increasingly difficult to come by. It seems to be easier to obtain a multi-million dollar grant for an accelerator or a giant telescope then to secure relatively modest support for a study of, say, the foundations of the theory of elastic instability.

A major share of the support for the university-based research has come from various federal agencies and from the different branches of the Department of Defense. The policies governing such federal funding have on the whole been enlightened in recognizing the specific nature of academic, as distinct from industrial research. One of the most significant functions of government research grants and contracts has been to sustain the advanced education of scientists and engineers, which is of equally crucial and obvious benefit to the country as a whole.

I personally owe a large and lasting debt to the Office of Naval Research, which for a period of over thirty years allowed me to pursue my research interests and to contribute to the training of graduate students, with essentially no interference and with a minimum of bureaucratic harassment.

Of late, however, federal support for academic research in engineering has taken a rather ominous turn. Apparently, while physicists or chemists remain free to do their own thing, engineers are to be held to delivering the goods. In particular, I gather that according to some recent edicts, research in applied mechanics is "to be made relevant to national defense" and is "to impact the competitive vitality of the economy" - if I may use some in-language. Since the National Science Foundation is presumably a guardian of fundamental research, I was all the more taken aback by a list of ten recommended research areas, which was distributed at an NSF conference on "Future Directions in Solid Mechanics Research", about a year ago.

My first qualms concerning this manifesto were aroused on noting that it comprised exactly ten items, "ten" being a conspicuously round number. I always suspected that the committee charged with drafting the Ten Commandments initially arrived at only nine and then added "Thou shalt not commit adultery" for good measure. I will not bore you by quoting the complete list of suggested research areas to which I am referring. Suffice it to mention that one of the categories listed is the "Mechanics of Modern Manufacturing", while another is headed "Mechanics in Strategic and Conventional Military Systems"; here "missile systems", "tube-launch systems", and "warhead design" are cited as representative examples.

I realize of course that this document originated in response to new government directives and that it is intended to make research in solid mechanics more attractive to those in control of funds. Yet if this is a vision of the future role of such research, I cannot help feeling that it is at best a vision impaired by a well-intentioned myopia.

There is a general consensus that research conducted at universities ought to be basic research. Admittedly, everyone has his own definition of "basic research", tailored to include his own work. But I cannot conceive of any acceptable definition that would accommodate the design of warheads.

Nor am I making a plea for the license to do irrelevant work. Bent on platitudes, I ought to remind you, however, that "relevance" is a slippery notion and that what is irrelevant or even frivolous work to some, may be regarded to be of fundamental worth by others. Finally, it is well to keep in mind that many of the most enduring and consequential contributions to applied science and engineering stem from research that was prompted by sheer intellectual curiosity and unencumbered by an insistence on its immediate applicability.

I must not test your patience by prolonging these opinionated and rambling ruminations. Otherwise I might suffer the fate of the speaker who apologized for having carried on interminably on the grounds that there was no clock within his view, only to provoke a member of his audience into pointing out a calendar on a wall of the lecture room.

Review articles on Flexible Electronics

2006-03-30T07:06:00.000-08:00

The cover story of the April 2006 issue of Materials Today features Flexible Electronics. This issue also includes two review articles in this emerging field of research. Access to full text articles is free of charge at http://www.materialstoday.com.

Review Article:
Material challenge for flexible organic devices, by Jay Lewis (My favorite)

Review Article:
Organic and polymer transistors for electronics, by Ananth Dodabalapur

Cover Story:
Jet printing flexible displays, by R.A. Street et al.

Enjoy.

Elements of Continnuum Mechanics by Romesh Batra

2006-03-30T04:59:00.000-08:00

Romesh Batra has recenly published a textbook entitled Elements of Continnuum Mechanics.

Learning from the dragonfly to engineer better flight

2006-03-28T04:25:00.000-08:00

Can the ability of the dragonfly to hover and maneuver provide insight for designing aircraft of the future? Read more.

1996 Timoshenko Medal Lecture by J. TINSLEY ODEN

2006-03-24T22:40:00.000-08:00

The Revolution in Applied Mechanics from Timoshenko to Computation

J. TINSLEY ODEN

The Applied Mechanics Division of the ASME established the Timoshenko Medal in 1957 to recognize distinguished work in the field. The first recipient was Stephen P. Timoshenko himself, an individual who contributed enormously to the prestige and strength of mechanics in this country and a legend whom I, as a young student in mechanics, looked upon as a special hero, one to be admired and emulated. To be honored by being awarded the Timoshenko Medal by the AMD is a very special event for me and one for which I will be eternally grateful. I will do my utmost to uphold the honor of the award and to live up to the high standard exemplified by its past recipients.

I begin this presentation with the somewhat conspicuous observation that during my career in applied mechanics, a special revolution has taken place which will forever change the subject and which will affect the way all science is done for rest of time. It is, of course, the emergence of the computer: computation providing a third pillar to the classical two pillars of the scientific method, theory and experiment, a pillar overlapping the traditional two but expanding each in ways never dreamed of in the days of Timoshenko’s work.

Before I comment further on this revolution, and my role in it, I will, as is customary in these events, first interject a few personal things that lay out the path that led me here. When I was young, a bout with pneumonia put me a year behind in school. When I got to college, I vowed to catch up, and so I finished a five-year program (154 semester hours) in three years, and a PhD in three more. So at the age of twenty five I began a career in research in mechanics and engineering computation. My own initiation into the modern computational side of mechanics came in the early 1960s. Equipped with a new PhD in traditional engineering mechanics from Oklahoma State, I joined the Research and Development Division of General Dynamics, Fort Worth in 1963, and was assigned to work with Gilbert C. Best to develop a computer program based on the finite element method, a promising new technology that GD thought might be of value in aircraft structural analysis and design. To work with Gil was an honor few had within the “bomber plant.” A completely self-educated man with a superior intellect, he quietly included me in his work on the grand project that, we thought, would revolutionize structural mechanics in the company. Though both of us had only a meager knowledge of FORTRAN in the beginning, we launched into a project that today I would not start without a team of ten or so collaborators, with PhDs in three or four fields. In around ten months, working long hours, we developed C-28, one of the first general-purpose finite element programs developed in the aircraft industry in the 1960s. It was a trial by fire; working many hours each week, we developed a long catalogue of finite elements for plates, shells, three-dimensional bodies, laminated composites, for modal analysis in structural vibrations, transient structural dynamics, for structural optimization, hybrid elements based on complementary energy principles and Reissner principles, many of these representing results which would not appear in literature for another fifteen years. We received a bit of internal acclaim and rewards for our work, but I, and I think Gil also, were perplexed about the fact that some of our schemes simply didn’t work. Convergence rates were impossible to predict, and the real mathematical bases of our schemes were obscure to us. We needed to learn more about the underlying mathematics, which at that time was unknown.

In 1964, I joined the Research Institute of the University of Alabama at Huntsville, home of the Marshall Space Flight Center, the Army Missile Command, and a hotbed of science and technology, with a new graduate program in engineering mechanics. There was no undergraduate program, eleven hundred excellent graduate students who had to learn enough to get a man on the moon in five years, and a graduate engineering faculty of around twenty five to thirty people. I taught virtually everything, from partial differential equations to complex analysis to continuum mechanics, to the beginnings of functional analysis and approximation theory, including a first full course, with personal notes, on finite elements, and another on finite element methods applied to nonlinear continuum mechanics. Gerry Wempner was a colleague there, and he provided counsel and criticism of my work, for which I am forever grateful. It was then that I began to understand and unravel the mathematical properties underlying finite element methods, and to apply them to problems in nonlinear continuum mechanics, particularly in finite elasticity, and beginning in around 1970, incompressible viscous flows. I moved to Texas in 1973, and have worked there on these and related subjects ever since, but my early inquiries into the mathematical basis of the computations led me to also venture into the mathematical side of theoretical mechanics.

But with the explosion in computational mechanics, beginning the 1960s, came an era in which computation was viewed with suspicion and mistrust by some of the mechanics community; the new methodologies and computing devices, put into the hands of inexperienced and untrained practitioners powerful tools that are easily misused and which, at first glance, could reduce the dignity and importance of the science. But, while abuses are always possible, a more mature appraisal reveals that computation has extended the vistas of mechanics to boundaries far beyond those of yesteryear to limits not yet known or well defined. I should say that the Applied Mechanics Divisoin has always appreciated the value of computation to mechanics; indeed, other computational mechanicians have been recognized as Timoshenko Medalists: Sir Richard Southwell in 1959, John Argyris in 1981, and perhaps others.

I think it is quite clear that computational mechanics has created a much more basic and fundamental view of mechanics than was traditionally thought possible. It has forced the mechanics community to reappraise the foundations of the subject as an engineering tool and to be conscious of the greater role played by mathematical modeling in engineering practice. Aside from some sentimental value, many of the approximate theories of mechanics, cherished when you and I were students, are reduced in their importance compared to a couple of decades ago, if not quickly becoming obsolete.

The successful engineering mechanician, these days, must have a more fundamental knowledge of basic mechanics than did his predecessors. Today, practitioners must understand and often deal with daily the fundamental concepts of kinematics, deformation, strain, stress, material behavior, thermal effects, etc.; and, they must have the mathematical machinery to characterize and cope with these concepts and to construct reliable numerical approximation. Thus, computation, this new tool, has forced us to develop a better, clearer idea of the processes we must use to do mechanics. The theory of the mechanical behavior of solids and fluids provides the basis for the development of mathematical models, and the understanding of the qualitative properties of these models and their numerical approximation has understandably exerted a greater demand on our use of mathematics and, perhaps surprisingly, has heightened rather than suppressed the need for deeper mathematics and more rigid adherence to mathematical rigor.

Timoshenko frequently expounded on the importance of mathematics as an inseparable thread interwoven into the fabric of mechanics. His work demonstrated time and again the interplay of mathematical modeling of mechanical events and the use of mathematics, not only as a language to communicate scientific thought, but also as a guide to physical experiments for measuring the behavior of material bodies under the actions of forces.

In my own experience, mathematics has transcended its classical role of merely the language used to describe models of nature; it has been elevated to a strange metascience, emerging in an almost spiritual way, that can provide insight into the very rules that nature imposes on the way physical events occur. I have experienced this phenomena many times. I am constantly amazed by it; but, find it difficult to explain or rationalize. How can these physical events that manifest themselves around us and which depend on the forces and material make-up of the physical universe be subordinate in any way to abstract rules of mathematics which are purely products of the human mind? This question, you see, elevates the role of mathematics far beyond that of a script we use to translate mental concoctions of how we expect nature to behave into models, but to a much more important role of actually dictating the features of models that are necessary to correctly depict physical events.

Perhaps this is because theoretical mechanics has itself influenced mathematics. This was certainly true a century ago and more, but the influence is less conspicuous today than it was in the days of early natural philosophy when mechanics and mathematics were so closely intertwined as to be almost indistinguishable. The fundamentally sound theories of mechanics, those which survived debate, study, scrutiny, testing, those which formed the foundations of the subject and were passed on to later generations, form the measuring stick against which good mathematics is measured. The interesting and often unexpected thing is that once the mathematics is established, it, in turn, provides a framework into which new mechanical theories must fit.

This idea of the role of mathematics is, as far as I know, a relatively new thing, but it may be ancient. I can cite many examples, but one that frequently comes to mind emerged in my work on friction models for dynamic contact in solid mechanics. The Signorini problem of linear elasticity, for example, provides a quite reasonable classical model of frictional contact of an elastic body with a rigid foundation. This is a perfectly satisfactory model for studying a variety of contact phenomena and has proved to be useful for more than a half century. But, when you add to the picture frictional phenomena governed by Columb’s law, an extension quite natural to beginning students of classical mechanics, the model completely degenerates! The very existence of solutions comes into question and was an open mathematical problem for 25 years. We know now that for certain ideal boundary and loading conditions, most of the solutions of frictional contact problems with Columb’s law found in the literature are probably correct, albeit not physically realistic, but we now also have concrete nonexistence results: solutions actually do not exist in some cases that, on the surface, might appear physically realistic, and this fact underscores that the crude characterization afforded by Columb should, in general, be used with great care or not at all.

To develop a model of frictional contact that is covered by a tractable existence theory, the mathematical characterization of friction and contact themselves had to be changed. I will never forget the excitement that came over me when I realized that the modifications of the model sufficient to allow existence of solutions and, in a sense, the well-posedness of the mathematical theory, were precisely those observed in many laboratory experiments. The physical parameters, for example, characterizing compliant interfaces were precisely those characterizing function spaces of traces of the stress vector on contact surfaces. This revealed an eerie and, to me, a special connection between the issues of modeling and the physical behavior observed in laboratory tests. Once this connection was observed, of course, the entire mechanics underlying the concept of dynamic frictional contact on elastic interfaces unraveled and became openly exposed and understood: physical insight, or hindsight as it may be, prevailed and old paradoxes and conflicts between theory and experiment were resolved, everything consistent with so-called engineering judgment; but the resolution of the paradoxes were uncovered by starting from a largely mathematical argument.

By the way, don’t confuse what I am saying about mathematical mechanics as any endorsement of the goal to axiomatize mechanics, a goal dating back to Aristotle and passionately followed during the 1960’s and an enterprise which some say failed. While I do not necessarily agree with that appraisal, here I am merely pointing to the fact that theoretical mechanics, indeed all of theoretical physics, is based on theories which are generally described in the mathematical framework that permits the construction of so-called mathematical models. These are mathematical abstractions that mimic idealizations of physical phenomena. This modeling, which again is a product of purely man’s intellect, of the human mind, has produced untold benefit to modern science and technology and has helped mankind exercise its control of its environment and its understanding of some of the secrets of nature. There is, in applying these models, a definite set of rules, a rigid dogma that must be followed if these models are to work, and this dogma itself is founded in mathematics.

Nowadays, there is a growing literature on methods to actually select the mathematical model itself. I view this as one of the most important developments in mechanics this century. It embodies a scientific method that addresses head on the most fundamental questions in applied mechanics—indeed in mathematical physics: what mathematical model must one choose in order to effectively study a well-defined class of mechanical phenomena? What spatial and temporal scales in the micromechanics affect the observed results in a substantial way? How do these subscale phenomena interact to produce meso or macro scale observations?

The resolution of these questions resides in the notion of hierarchical modeling, of a posteriori modeling error estimation, and of adaptive modeling, mathematical notions that arise naturally in proper mathematical frameworks of important problems in theoretical and applied mechanics, but which, when properly implemented, will require cutting-edge computational science as well. It is a subject that, for example, will revise completely the way we deal with composite materials, multi-phase flows, damage mechanics, and eventually even turbulence. It is a subject of great interest to me and one I am convinced will have a fundamental impact on theoretical and applied mechanics in the future.

As I reflect on this event, I share the sentiments of a recent Timoshenko Medalist, John Lumley, who said, “As I have gotten older, I have found that more and more I am a research administrator. I am sure I am not unique-this happens to all of us, but it is a bit sad. That is, I have less and less opportunities to do things for myself. I am supervising others who have all the fun.” Nevertheless, there is too much new, exciting, worthwhile, and challenging opportunities to let others have all the fun. I plan to find time to be in on some of the great things in store for Applied Mechanics in the future.

Once again, I thank the Applied Mechanics Division for this singular honor. I know that such awards do not happen accidentally, but require the generous support of friends and individuals in the mechanics community, and for these unnamed supporters, I give my most sincere thanks. I reiterate my promise to steadfastly uphold the honor of this award, and to hold it with the dignity exemplified in its namesake, Stephen P. Timoshenko. Thank you all for your generosity and, to all, my best wishes.

The MacTutor History of Mathematics archive

2006-03-23T12:33:00.000-08:00

This archive, developed by two professors of mathematics, hosted by the University of St Andrews, Scotland, contains biographies of many mathematicians. It also contains biographies of quite a few mechanicians, including

George Keith Batchelor (1920-2000)
Michael James Lighthill (1924-1998)
Sydney Goldstein (1903-1989)
William Prager (1903-1980)
Geoffrey Ingram Taylor (1886-1975)
Theodore von Kármán (1881-1963)
Richard von Mises (1883-1953)

All but Mises in the above list won the Timoshenko Medal.

Response/Feedback requested: Journal Club?

2006-03-21T12:09:00.000-08:00

Hello everyone,

I would like to solicit feedback and comments on an idea to further enhance the role and utility of this blog.

This inspiration comes from Bell labs and the physics community.....

They started a journal club (year 2003). Each month ONLY 2-3 already published recent journal papers are reviewed and commentary posted in the form of a newsletter. Since only 2-3 papers are reviewed, the selection is much more stringent and careful. The contribution is regular and periodic (monthly). Hence, this newsletter is take very seriously by physicists.

In our case, this can be done within our blog. I suspect we could achieve the same kind of interest if we restrict "notable" papers to 1-3 per month and make it a regular monthly feature. In principle anyone could submit a commentary but the blog moderators will select the top 2-3.

Please leave your comments below. Thank you.

A Tribute to Professor T.H. Lin’s Most Distinguished Career

2006-03-20T16:14:00.000-08:00

In conjunction with

The 2006 Seventh World Congress on Computational Mechanics
Century City, Los Angeles, California
July 16—22, 2006

By Woody Ju

To honor the 95th birthday and the most distinguished lifetime career of Prof. T.H. Lin, we are organizing a very special symposium, entitled “T.H. Lin 95th Birthday Symposium on Computational Mechanics and Materials”, to be held on July 16-22, 2006, at the Hyatt Regency Century Plaza Hotel, in conjunction with the 2006 7th World Congress on Computational Mechanics.

Professor Lin was born in China in Year 1911. He was among the first groups of Chinese students and scholars to study in the U.S., arriving at MIT in Year 1934 after a historic selection process. During the World War II, Professor Lin decided to join the war against Japan by returning to China, and he built the very first airplane in China under the sponsorship of the Nationalist Government during WWII. Since no test pilot was willing to test fly his first-ever Chinese designed and manufactured twin-engine “China Transport No. 1” airplane at the time, Professor Lin risked his own life being a passenger with the test pilot on the successful virgin test flight in Year 1944. Professor Lin is truly the father of aviation in China. After WWII, Professor Lin returned to the U.S., pursued his Ph.D. degree at the University of Michigan, and worked as an Associate/Full Professor at the University of Detroit. In 1955, he joined UCLA and became (most likely) the first Asian-American professor on campus.

Professor Lin has made seminal and most important contributions to the field of solid mechanics and materials science, particularly involving crystal plasticity, dislocations, persistent slip bands (PSB) in metals, and micromechanics of creep and fatigue microcrack initiation in metals. Plastic deformation in metal requires the motion of dislocations. As they move through materials, screw dislocations cross-glide from one glide plane to another, and back again, leaving edge dislocation dipoles in their wakes. These dislocation dipoles are persistent since they can only be removed through diffusion. They cause strain-hardening and degradation of the strength of the material, leading to the initiation of fatigue micro-cracks, and eventually to fatigue failure. Among his other prominent scholarly work, Professor Lin has made historic landmark contributions in the above research field. His 1968 book on “Theory of Inelastic Structures” carried monumental influences for plastic analysis of solids and structures. Professor retired from UCLA in 1978, but he continues his active research in plasticity to this day (at the age of 95).

Professor Lin has received numerous awards and honors in his seven-decade most distinguished career, including the 1988 ASCE Theodore von Karman Award and the 1990 election to the U.S. National Academy of Engineering.

Professor J. Woody Ju (UCLA) and Professor George J. Weng (Rutgers University) organized a memorable special T.H. Lin 90th Birthday Symposium on Mechanics and Materials in June 2001, in connection with the 2001 Joint ASCE-ASME-SES Mechanics and Materials Conference at San Diego, California. A special Ginkgo tree was planted in front of the UCLA Boelter Hall (School of Engineering) on June 29, 2001, to honor Professor Lin’s distinguished career and life long contributions to UCLA and the field of mechanics and materials; see Photo 1. This time, Professor J. Woody Ju and J.S. Chen (UCLA) and Professor Lizhi Sun (UC Irvine) are truly honored to organize this historic T.H. Lin 95th Birthday Symposium on Computational Mechanics and Materials in July 2006 at Los Angeles. We sincerely and respectfully wish Prof. Lin a very special and happy birthday at age 95, and offer our best wishes for many more good years to come for Professor Lin!

Professors T.H. Lin and J. Woody Ju (Author) in front of the special Ginkgo tree in honor of Professor Lin’s distinguished career and contributions, in front of UCLA Boelter Hall, after the tree-planting ceremony on June 29, 2001.

Is rest of the world catching up with us? Perspective from Physical Review Letters...

2006-03-19T13:52:00.000-08:00

Recently I attended the annual American Physical Society conference held in Baltimore (during the week of March 13th). One of the non-technical sessions included presentations by the APS journal editors--Physical Review A/B/C/D/E and Letters---and a panel discussion related to these journals. Since many of our mechanics and materials colleagues nowadays are interested in publishing in these journals, I thought I should post a link to some of the slides (from the editors presentation) that I found interesting. Many of the slides presented at APS are in the linked pdf file that also includes additional (humorous slides!) regarding reviewer issues.

Essentially, the graphs in the presentation depict a telling trend regarding globalization of research. Until 1995, US submissions to PRL dominated with western Europe and rest of the world following (in that order). In 1995, western Europe overtook US. Since last year, the rest of the world has overtaken BOTH western Europe and US. By the "rest of the world", the editor is essentially referring largely to China, and partly to India and eastern Europe.

2002 Timoshenko Medal Lecture by John W. Hutchinson

2006-03-19T08:43:00.000-08:00

LIFE AS A MECHANICIAN: 1956-

John W. Hutchinson

This is a great honor for me; I know that I am undeserving. Nevertheless, I will gladly accept the medal. Several weeks ago, the NPR journalist, Daniel Schor, was elected to the American Academy of Arts and Sciences, and in his acceptance speech he remarked that he had learned how to be gracious about undeserved honors from Henry Kissinger. Shortly after Kissinger received his Nobel Peace Prize, a reception in his honor was held at the State Department. An elderly woman approached Kissinger, grasped his hand, and thanked him from the bottom of her heart for saving the world. Following one of his heavy pauses, Kissinger replied, “you’re welcome”. In my case, I can thank you because, in addition to recognizing whatever contributions I have made to mechanics, the medal recognizes contributions of the teachers, colleagues and students with whom I have had the pleasure to interact over many years. In fact, I have always felt that the Timoshenko Medal is above all else a celebration of mechanics as a wonderful field. We have the great luxury to work in a field where basic math and science mix side by side with engineering applications. In any given day it is not unusual for our thoughts to range from the highly theoretical to very practical. I’d like to use my twenty minutes before you tonight to give a few randomly selected, personal reminiscences about some of the subjects on which I have worked with asides on a few the people in our field that I have had the pleasure to know. Speaking of this, I must mention that, although I cannot claim to have known Timoshenko, I did have the pleasure of meeting him briefly very early in my career. I’m not sure how much longer our Timoshenko Medalists will be able to make this claim. I will also say that I pick up one of his books on the average about once a month.

For me professionally, mechanics has been structures, fracture and materials. If you think back to 1956 when I started college, you will recall that computers were just beginning to be used to solve structural problems, fracture was just beginning to develop as an engineering science, and the mechanicians working on materials could be counted on the fingers of one hand. How things have changed! Those of us here over fifty or so have all been at the center of this revolution, most of the time without realizing that a revolution was underway. I will not be putting special emphasis on the role of computers in mechanics, even though this is like ignoring a bull in the china shop. The computer has transformed not only our field, but most fields of engineering and science. We can be proud that it is our colleagues in mechanics who led the way in developing the some of the most powerful numerical methods for engineering problems. In recent years the Timoshenko Medal has gone to some of the pioneers of the finite element method. I’ve been a user of computers, but not a developer of numerical methods, per se, so I am happy to leave it to future colleagues to tell us more about the ongoing developments on the computational side.

When pressed to state what I regard as the most remarkable single contribution of an individual in solid mechanics in my lifetime, I am inclined to say that it was Warner Koiter’s Ph.D. thesis, “On the stability of elastic equilibrium”, published in Amsterdam in 1945. The thesis developed the theory of elastic buckling and post-buckling behavior, the effect of initial geometric imperfections on buckling, and applied this theory to columns, plates and shells. But that was not all, most of Koiter’s subsequent seminal contributions to shells, both linear and nonlinear, had their beginnings in his thesis, and many aspects were already well developed there. I take pride in the fact that Bernie Budiansky and I were among the first to discover Koiter’s thesis, and that was not until 1963. Incidentally, the thesis work was carried out during the war in occupied Holland. Koiter later told me he did much of the work in a closet by the light of a candle—he may have been exaggerating. The thesis was published in Dutch. Budiansky and I relied on our astrophysics colleague, Max Krook, who knew Afrikaans and, therefore, a little Dutch to provide us translations of critical sections. Some years later, after Koiter’s approach was widely appreciated, I naively asked Koiter why he had never published his work on stability. He looked at me down his long nose and informed me it had been published! In Dutch, as his thesis! Shell buckling was one of the hot areas in the 60’s, motivated by rockets and other aerospace structures. The perplexing aspect everyone was trying to come to terms with at the time was the notorious discrepancy between the collapse load of actual shells and what was predicted theoretically for buckling of a perfect shell. Thin cylindrical shells under axial compression were observed to collapsed at loads as small as 20% of the theoretical prediction in contrast to columns and plate structures which showed good agreement between experiment and theory for the perfect structures. The key to understanding the discrepancy was the highly nonlinear post-buckling behavior and the extreme sensitivity to imperfections, which were related and clarified by Koiter’s thesis. Skeptics at the time thought that the basic theory for the perfect shell was intrinsically flawed, but it wasn’t. In fact, in the late 60’s, Rod Tennyson at the University of Toronto succeeded in making shells so nearly perfect that they buckled within 95% of the prediction for the perfect shell. All that is now history. Buckling problems of all kinds arise continually in many areas of technology. Sometimes I wonder where the expertise on buckling will reside when all of us aging bucklers cross the bar. ABAQUS can solve buckling problems, but it can’t pose or understand them. I’m afraid it would not take long to count the number of courses on buckling now taught in this country. On that somewhat pessimistic note, I’ll move on to fracture.

I was born a few years after Griffith wrote his landmark paper on the fracture of glass, but all the other developments of fracture mechanics occurred during my lifetime and most of them occurred during my lifetime as a mechanician. It is worth extolling fracture mechanics since to me it represents mechanics at its best: mathematical theory and problem solving (analytical and numerical), strong experimental underpinning, test method development, and, last but not least, engineering applications and materials characterization. All these are mixed together in an essential and rich manner. Fracture mechanics is going strong after fifty years of development. Fracture problems also arise every day in many areas of technology, and fundamental connections to microscopic and atomistic failure processes will continue to challenge some of us for many years to come. The chief limitation of fracture mechanics is simultaneously its great strength—namely, the details of the failure process are all swept under the rug as a critical parameter to be measured by experiment. Thus, crack mechanics provides a framework for carrying out macroscopic measurement and application of behavior that is controlled at much smaller scales, even at the atomic scale in some instances. Tests are designed to measure material toughness, or crack growth rate, and then this data could be applied to predict the integrity of a structure. I think I am correct in saying that after fifty years of measuring toughness and fatigue crack growth rates experimentally, there is probably not a single instance where a critical application has made use of toughness that has been predicted theoretically. You have to give the earlier developers a great deal of credit for understanding this from the start—I’ll single out George Irwin and Paul Paris as two of many of our colleagues who had the great insight to set this in motion. Paris’s early contribution was not the Paris Law (Paris, himself, is always the first to say it is no law at all). Along with Irwin, his contribution was the recognition that a truly esoteric quantity from elasticity theory, the stress intensity factor, could be used to develop a framework to measure crack growth and predict structural integrity.

Two motivations drove the development of nonlinear fracture mechanics. One was the quest to characterize behavior nearer the tip where the fracture process occurs. But equally important was the more practical problem of the huge specimens required for measuring fracture toughness based on linear fracture mechanics of the tough, ductile steels used in the nuclear reactor industry. In the late 60’s and early 70’s, engineers at Westinghouse were using specimens the size of a large file cabinet and weighing several tons to determine the toughness of pressure vessel steels. For every set of conditions, several specimens must be tested. Even for the most important applications, this was untenable. Thus, Jim Begley and John Landis at Westinghouse had plenty of motivation to see if they could make use of Jim Rice’s J-integral theory when extensive plasticity occurs, in analog to the way the stress intensity factor is employed when the deformation is elastic. It worked, not immediately, of course, but after the usual hard work. Now the fracture toughness of very tough steels can be measured using small specimens, thanks to a healthy mix of theory and experimentation. It has to be emphasized that this approach is still phenomenological—just like the linear approach it makes no pretense at incorporating a description of the microscopic fracture process. A computational approach to crack growth in ductile alloys based on the mechanics of the fracture process began to emerge in the early 70’s, motivated by problems in the nuclear power industry. Just when progress started to be made, the Nuclear Regulatory Commission and EPRI, who were supporting most of this work, stopped the funding. It took almost a whole decade before groups working independently in France, Germany, the UK and America moved ahead on this more fundamental approach. While much remains to be done on the nucleation and propagation of cracks in tough, ductile alloys, the approach appears to be the first computational method based on microscopic fracture processes that is ready as an engineering tool. I would be remiss if I did not emphasize that this approach still requires experimental calibration. As I said in the beginning of my remarks on fracture mechanics, toughness is measured not predicted, and I suspect this will just as true ten years from now.

Fracture mechanics remains a remarkably vital subject, and I’ve only scratched the surface of the history. Nevertheless, it is time to expand into my last period, materials, which is an even larger subject and which I will treat even more cursorily. The mechanics of materials has been around a long time, but back in the early 1960’s mechanicians working on fundamental aspects of material behavior were few and far between. Certainly, Frank McClintock deserves special mention as one of the earliest of the modern generation. As an undergraduate applying to graduate school, I recall being told by C.C. Lin, an eminent fluid mechanician at MIT, that materials (not plastics, incidentally!) were the future for a young man. Indeed, by the mid¬1970’s, structures had definitely lost out to materials as far as attracting the attention of many of us. Looking back, one can see that the emerging interest in materials had an enormously energizing effect on solid mechanics. So much so, that I remember friends in fluids wistfully envying our great source of problems. There is an enormously rich set of physical phenomena at many length scales associated with materials, and mechanics seems to be uniquely suited to organizing the interplay among the multitude of influential factors. Incidentally, color is not necessarily one of the influential factors, as this story will relate. I had worked on the transformation toughening of a ceramic, zirconia, for over a year and was giving a talk on the subject, when someone in the audience had the audacity to ask me for the color of zirconia. I hadn’t a clue, of course. For about the last twenty years, I’ve had the great fortune to work closely with Tony Evans on many different materials engineering problems. Evans knows that too much information will confuse any mechanician, and he has always been very selective about the facts he feeds me. Needless to say, the color of zirconia was not one of them.

The subject of materials is too big for an after dinner talk, apart from some light hearted remarks. I’ll repeat the advise that Rod Clifton gave to young mechanicians when he was up here a couple of years ago-- young man or young woman, its biological materials.

I’ve already remarked on the wonderful mix of theory, experiment and application comprising mechanics: a veritable melting pot of engineering, mathematics and physics. Lying at the crossroads of such intellectually diverse fields can create tensions. When I was a young fellow, there was a decided tension between colleagues who viewed mechanics as rightfully belonging to the field of mathematics and those who saw mechanics as part of engineering science. One of the first technical meetings I attended was the US National Congress of Theoretical and Applied Mechanics at the University of Minnesota. For the opening general lecture, Clifford Truesdale gave a lecture with a distinctly mathematical tilt on nonlinear continuum mechanics. George Carrier, a colleague of mine in fluid mechanics from Harvard, gave his general lecture on oceanography the following day. To the great amusement of his audience, he spent the first few minutes of his lecture mimicking Truesdale by giving an overly formal mathematical definition of an ocean. Without slighting the contributions of our former colleagues on either side of the fence on this issue, I think nearly all of us here will agree on how this tension has played out. Leaving aside who foots the bills for our research, mechanics is rightfully part of engineering and science. The fact that mechanics abounds with so many wonderful mathematical problems is a seductive added bonus.

Colleagues of my generation owe much gratitude to the Russians for stimulating the flow of research funds and university expansion in engineering and science. I was a sophomore in college when Sputnik went up, and it is only a slight exaggeration to say that I surfed the wave that Sputnik generated for many years afterward. The high flying years in the 1960’s in engineering and science funding contributed to unrealistic expectations in later years, which haven’t completely faded away. I’m going to resist the temptation to speak on the erosion of funding for mechanics in the current environment, which provides grist for many a Timoshenko after dinner talk. The idea of funding for research in mechanics, as if it were a basic science or mathematics, is a product of the two trends of the 60’s that I just mentioned. That is, mechanics as mathematics rather than engineering science, and the overly flush period in the 60’s when funding could be had for almost any reasonable research project in the physical sciences. My younger colleagues here may regret not experiencing the largess of those earlier years, but at least you are spared from forming habits that are hard to shed. On the positive side, we in mechanics work on a vast array of subjects within engineering and science, and we draw our support form an equally broad range of sources, even if we have to scramble to do it. As a community, our interests are much more diverse than in the “good old days”, which of course presents both benefits and difficulties to the field of mechanics per se.

In closing I want to pay special tribute to the extraordinary colleagues with whom I have had the great fortune to share this profession, colleagues at Harvard and at many Universities in the US and abroad. Among these colleagues have been many exceptional graduate students. Indeed, some have been so exceptional that they needed almost no help from me at all, and I hardly remember them setting foot in my office. As I said at the start, the Timoshenko Medal is the recognition that means the most to me. From here on out, I’m happy and no further recognition is necessary. I’ll be working purely for the pleasure of mechanics itself. Some of you probably saw the interview with Duke Ellington in the Ken Burns series on American Jazz, held near the end of Ellington’s career when he was in his eighties. Ellington was asked, which of all the songs he had composed did he like the best. “The one I am working on at the moment”, Ellington replied. And so it is in mechanics!

2006 Gordon Research Conference

2006-03-18T12:12:00.000-08:00

Registration is now open for the 2006 Gordon Research Conference on Thin Film and Small Scale Mechanical Behavior.

Bernard Budiansky (1925 - 1999)

2006-03-18T04:59:00.000-08:00

Bernard Budiansky was an unabashed enthusiast about his profession, family, friends, and many other good things in life. He made innovative contributions to nearly every subfield of solid mechanics — the science of how materials and structures stretch, shake, buckle and break. His work as an applied mathematician and mechanical engineer strongly influenced structural engineering and materials technology, and even seismology and biomechanics. Read more...

Journal of Mechanics of Materials and Structures

2006-03-17T05:54:00.000-08:00

Launched in January 2006, this journal takes a fresh approach to disseminate innovative and consequential research in mechanics of materials and structures of all types. Read more.

Cosmic 'DNA': Double Helix Spotted in Space

2006-03-15T19:13:00.000-08:00

I came cross this headline in Yahoo news. It's amazing! check it out.

Dynamic Shear Rupture in Frictional Interfaces: Speeds, Directionality and Modes

2006-03-15T16:52:00.000-08:00

By Ares J. Rosakis, et al, California Institute of Technology

The goal in designing dynamic frictional experiments simulating earthquake rupture has been to create a testing environment or platform which could reproduce some of the basic physics governing the rupture dynamics of crustal earthquakes while preserving enough simplicity so that clear conclusions can be obtained by pure observation. In this article we first review past and recent experimental work on dynamic shear rupture propagation along frictional interfaces. The early experimental techniques are discussed in relation to recent experimental simulations of earthquakes which feature advanced diagnostics of high temporal and spatial resolution. The high-resolution instrumentation enables direct
comparison between the experiments and data recorded during natural earthquakes. The experimental results presented in this review are examined in light of seismological observations related to various natural large rupture events and of recent theoretical and numerical development in the understanding of frictional rupture. In particular, the physics and conditions leading to phenomena such as supershear rupture growth, sub- Rayleigh to supershear rupture transition and rupture directionality in inhomogeneous systems, are discussed in detail. Finally, experiments demonstrating the attainability of various rupture modes (crack-like, pulse-like and mixed) are presented and discussed in relation to theoretical and numerical predictions (the complete article).

Notes of AMR administrator: Dr. Ares J. Rosakis, Theodore von Karman Professor of Aeronautic and Mechanical Engineering at Caltech, and his colleagues have recently made siginificant contributions to earthquake dynamics and supersonic wave propagations in solids (e.g. Science 29 April, 2005; Science, 19 March, 2004).
The above article is a review article by Prof. Rosakis and his colleagues, which will be published in the Treatise of Geophysics.
For more information about Professor Rosakis' recent research on earthquake dynamics, you can visit this website.

Continuum Mechanics books, Abramowitz and Stegun, downloadable

2006-03-15T14:30:00.000-08:00

Books on continuum mechanics freely available on the web. Of particular note,

"Introduction to Continuum Mechanics for Engineers" by Ray M. Bowen
http://www1.mengr.tamu.edu/rbowen

"Continuum Mechanics" by George Backus
"Continuum Mechanics" by Brian Kennett
both at http://samizdat.mines.edu
The samizdat site has links to many other texts, particularly in geophysical applications.

Not continuum mechanics but useful if you have ever used the hard copy:
"Abramowitz and Stegun: Handbook of Mathematical Functions"
The copyright is in the public domain. The book can be downloaded from http://www.math.sfu.ca/~cbm/aands
Keep the html version on your PC and you can get that Bessel function relation in no time.

AMR will be more useful if we recommend papers from all sources

2006-03-14T08:06:00.000-08:00

From time to time, the contributors of Applied Mechanics Research and Researchers (AMR) recommend papers that people in our community may appreciate. So far most recommended papers are those recently published in popular journals (e.g., Science, Nature, PRL and PNAS), or prominent journals in our own field (e.g., MRS Bulletin and JMPS). I believe that AMR will lose much of its utility if we keep recommending papers from well-known sources. These papers need little recommendation, and by doing so we do not provide much value to our community. How about a remarkable preprint, or a paper published in a less known journal, or an obscure old paper that deserves our attention now?

I believe that another practice has restricted the utility of AMR. To avoid self-promotion, initial contributors of AMR agreed that we would not post any entries of our own work. Now this unwritten rule has turned into a practice. Perhaps we should reexamine this rule for a very simple fact: most researchers are at their best when articulating their own work. Furthermore, it has been a long tradition in our field to place our own work in the context of works of others.

How about we simply let our contributors recommend any paper, regardless of its source, so long as the paper is remarkable and is of interest to the community of Applied Mechanics? I believe that our contributors, when posting an entry of their own work, will go out of their way to credit other people.

That’s the thought of the day. Please feel free to leave your comments below.

2004 Timoshenko Medal Lecture by Morton E. Gurtin

2006-03-10T18:24:00.001-08:00

Confessions of a slightly frayed continuum mechanician

by Morton E. Gurtin , November, 2004

This award is a great honor: although I’m a mathematician, my career began as a mechanical engineer. After graduating from RPI with a Bachelor’s degree in Mechanical Engineering, I worked as a structures engineer for Douglas Aircraft and for General Electric, where I spent many hours studying Timoshenko’s books on vibration analysis and plates and shells.

My third year at General Electric was in a consulting group concerned with structures and vibrations. My work was interesting: during one period I worked on a problem involving a vibrating washing machine and at the same time performed a vibration analysis of a nuclear aircraft-engine. Our group consisted almost entirely of Ph.D.’s, and I wrote a few papers on topics related to my work. I was greatly influenced by two colleagues, Bob Plunkett and Paul Paslay, who strongly suggested that I go back to school. Under their counseling I applied to Stanford and MIT in Engineering Mechanics and to Brown University in Applied Mathematics. My first choice was MIT, but because of my college-grades (which is another story for another time) MIT offered me a probationary assistantship, but Brown ignored my grades and offered me a National Defense Fellowship, which I accepted.

I wrote my thesis with Eli Sternberg and remained on the faculty for five more years. During my last few years at Brown the department became factionalized, with Ronald Rivlin on one side and the remaining senior faculty on the other. Midafternoon the faculty would have coffee at a nearby delicatessen. This could be unpleasant, as it was necessary to decide with whom to sit. I solved this problem by going to coffee with Jack Pipkin, another young faculty member, and sitting with him. I’ve heard all sides of the story behind the split, and to this day don’t understand what happened; all I know is that it made my last few years at Brown very difficult. Things were so bad that almost the entire senior faculty left within a three year period.

The direction of my scientific career was changed by Clifford Truesdell’s classic 1952 paper on nonlinear continuum mechanics and Walter Noll’s thesis, written in 1955. These papers and a course I sat in on by Albert Green introduced me to the rational study of nonlinear continuum mechanics, a subject I have pursued ever since. A scientist who had great influence on my work was Bernard Coleman. His papers, partly in collaboration with Noll, made thermodynamics understandable, at least to me. I had detested this subject since my undergraduate days at RPI, where thermodynamics was synonymous with steam tables. Coleman had a marvelous knowledge of the physical world and worked with great intensity. We would discuss work over the telephone, usually after midnight. One problem with Coleman is that he loves to talk and hates to end a conversation. Often I would put the phone down and work until I stopped hearing his voice; I would then pick up the phone and say; ``Bernard, I agree completely''.

As a young faculty member I was asked by Josef Meixner and Joseph Kestin, who were thermodynamicists, and Rivlin to present some lectures for the faculty on the thermodynamics developed by Coleman and Noll. Meixner, Kestin, and Rivlin despised this work, as did most senior people working in thermodynamics and continuum mechanics. They did not like the idea of defining temperature outside of equilibrium, they did not like the idea of entropy as a primitive quantity, and they did not like abandoning the classical ideas of state. I was attacked continually during these lectures, with Rivlin, who has a great sense of humor, continually making jokes, mostly at me expense, but I do believe I held my own. Today the Coleman-Noll view of thermodynamics is generally accepted by workers in continuum mechanics, most often without acknowledgment, but a generation of scientists had to be replaced.

I have had more angry discussions about thermodynamics than about any other scientific topic. Thermodynamics is a strange, almost mystical subject. It is at the same time both abstract and practical. It’s been my experience that engineers and applied scientists don’t often understand the nature of primitive objects in a physical theory: in books on thermodynamics one often finds temperature defined in terms of entropy on one page and entropy defined in terms of temperature a few pages later. This type of circular reasoning along with pseudomathematical definitions of standard mathematical objects lead students to either reject the subject or to accept it with an almost religious zeal.

In the midsixties Coleman and I, in partial collaboration with Ismael Herrera, wrote a series of papers on wave propagation in materials with fading memory, which is a fancy way of saying viscoelastic materials. When I presented this work at Brown I was attacked by many of the faculty who said that, because of dissipation, the waves of discontinuity that our theory predicts could never exist. Jack Pipkin agreed with this point of view, and told me that he was going to use a simple model to show that our theory was flawed. A few days later Jack came to my office and said that we were correct; his model established the actual existence of these waves. Later we found an earlier paper by Lee and Kanter that did the same.

Through the years I have learned that in physics intuition can often be misleading: it’s an excellent guide but a poor leader. During a visit to Brazil I worked on the thermodynamics of diffusing, chemically reacting materials with a chemical engineer to whom I will refer as V. Thermodynamics often leads to an inequality involving the relevant fields. When I showed V the inequality I had derived he became very excited and lectured me for an hour on how this inequality, as interpreted term by term, made perfect physical sense. That night I discovered that the inequality went the other way. The next day V gave me another lecture demonstrating the physical correctness of the reversed inequality.

By the Fall of 1965 all of my continuum mechanics colleagues except Pipkin and Rivlin had left Brown, and I left in 1966. My departure from Brown made me very sad, as I really loved the place. I always felt I would return, but that never happened.

This is the approximate midpoint of my talk and it reminds me of a workshop chaired by L. C. Young, a great mathematician and the originator of Young measures, a mathematical tool central to the study of phase transitions. Young, then approximately 80 years of age, was asleep at the front of the room. The speaker was midway through the talk and a question from someone in the audience resulted in an animated discussion with the speaker. The discussion woke up Young who sat quietly listening and when the discussion ended Young stood up and said: ``Well, if there is no further discussion, let’s give our speaker a great big hand and retire for lunch.”

And, while we’re in a nonserious mood, let me add a quote from the writer Frederick Raphael about awards: Awards are like hemorrhoids; in the end every asshole gets one.

The early years at Carnegie Mellon were wonderful. We were possibly the best place in the world for nonlinear continuum mechanics. The 60’s, driven by the research of Toupin, Ericksen, Noll, and Coleman, saw the solution of many of the conceptual problems that had plagued continuum physics, and much of this work was carried out at Carnegie Mellon.

One of the main things I learned during this period is the importance of concepts, of ideas. There are many levels of understanding: a theory generally has a few major ideas that form its backbone, and these are usually discovered first, but the real understanding lies in the interconnections that arise when layer after layer of extraneous material is removed. I learned most of this from Walter Noll, who is the deepest mathematician I have known.

Because the basic framework of continuum physics was not well understood prior to the 60’s, the work during the 60’s was often axiomatic. Unfortunately, the insistence on axiomatics later became a disease in which ideas of little depth were flowered with trivial demonstrations of rigor; also, unfortunately, I was one of those stricken with this disease.

In 1975 Jerry Ericksen wrote a paper on the equilibrium of bars that instituted phase transitions as a branch of continuum mechanics. Ericksen, who was central to the 60’s renaissance of continuum mechanics and well known for his pioneering work on liquid crystals, began in the mid 70’s applying continuum mechanics in situations for which behavior at microscopic scales becomes important. Concurrently materials scientists such as Cahn, Eshelby, Frank, Larchie, and Mullins, among others, were developing theories of multiphase systems based on ideas of Gibbs and Herring. A central outcome of this work was the realization that problems involving phase transitions with sharp interfaces generally result in an interface condition over and above those that follow from the classical balances for forces, moments, mass, and energy. Granted equilibrium, this extra balance may be derived variationally, but such a variational paradigm is not available for dynamics; even so, materials scientists typically use, for dynamics, the variationally-derived interface condition for the system at equilibrium. In studying this body of work one is left trying to ascertain the status of the resulting interface condition: is it a balance, is it a constitutive equation, or is it neither? Successful theories of continuum mechanics are typically based on a clear separation of balance laws and constitutive equations, the former describing large classes of materials, the latter describing particular materials.

That additional configurational forces may be needed to describe phenomena associated with the material itself is clear from the seminal work of Eshelby, Peach and Koehler, and Herring on lattice defects. But, again, these studies are based on variational arguments, arguments that, by their very nature, cannot characterize dissipation. A completely different point of view was taken by Allan Struthers and me in 1990; using an argument based on invariance under observer changes, we concluded that a configurational force balance should join the standard (Newtonian) force balance as a basic law of continuum physics.

Over the past ten years of so — partially in collaboration with Paolo Cermelli, Eliot Fried, and Paolo Podio-Guidugli — I have used configurational forces, with its peculiar balance, to discuss a variety of phenomena, examples being solid-state phase-transitions, solidification, grain-boundary motion, and epitaxy. In a forthcoming study, Cermelli, Fried, Dan Anderson, Jeff Mcfadden, and I discuss fluid-fluid phase-transitions; here the extra interface condition, being viscous, cannot be determined using a variational paradigm.

As a graduate student I was strongly influenced by a point of view — of my advisor and of others working in nonlinear continuum mechanics — that plasticity was not a field worthy of study because of its `` rotten foundations''. This view was strengthened by an undecipherable course taught by a major name in plasticity theory. But time has taught me that such a view is snobbish and unintellectual: if a theory that predicts well the qualitative behavior of real materials has questionable foundations, then, for a person interested in the foundations of continuum mechanics, that is all the more reason to study it.

Based in part on work of Aifantis, Anand, Asaro, Fleck, Hutchinson, Mandel, Needleman, and Rice, in part on my own work on phase interfaces, and in part on discussions with Lallit Anand, Alan Needleman, and Erik Van der Geissen, from which I have gained much, I have become interested in the description of crystalline and isotropic plasticity at small length-scales via dependences on strain gradients. Underlying my work is an accounting for the power expended by microstresses conjugate to plastic strain-rate and plastic strain-rate gradient, an accounting that leads naturally to a microforce balance for the microstresses that, with thermodynamically consistent constitutive equations, forms a flow rule in the form of a nonstandard partial-differential equation requiring boundary conditions. The resulting theories are shown to exhibit two distinct physical phenomena:

(1) energetic hardening associated with plastic-strain gradients and resulting in a size-dependent back-stress as well as boundary-layer effects;

(2) dissipative strengthening associated with plastic strain-rate gradients and resulting in a size-dependent increase in yield strength, with smaller being stronger.

The work on energetic hardening is in partial collaboration with Bittencourt, Cermelli, Needleman, and Van der Geissen; the work on dissipative strengthening is joint with Anand, Lele, and Gething; the strenghening phenomenon was discovered independently by Fredricksson and Gudmundson.

This recent excursion into plasticity has demonstrated to me, once again, the power of continuum mechanics and the importance of collaborations between continuum mechanicians of my ilk and engineers more interested in applications. But, unfortunately, at a time when technology requires sound models of exotic materials and of materials applied at smaller and smaller length scales, continuum mechanics is dying. This subject, with its focus on the rational formulation of theories and on the unification of disparate theories, is being dropped from engineering curricula in favor of separate sometimes archaic courses in solids and fluids — and this at a time when materials whose underlying structure is neither solely solid nor solely fluid are being developed and utilized. Ironically, physicists in droves are now turning to the use of continuum models, but are doing so without even a minimal understanding of the underlying mechanics. I am deeply saddened by this situation, and I don’t see it improving in the near future.

In discussions regarding life-choices I am often asked if I enjoy being a mathematician. My answer is always the same: I’m a lucky person; I can’t believe I get paid to do what I do. It’s diffcult to describe to a lay person that wonderful, almost magical moment of revelation in the solution of a problem or in the understanding of a concept. The problem or concept need not be grandiose, or even important, and often it is forgotten the next day.But that seems unimportant.

I try to frame rational theories of continuum physics. Once in a while I am successful, most often I am not. And the work is very painful. But the successful theories are worlds, exciting worlds through which I can roam, perhaps for just moments, but those moments, like no other, are free of the ambiguity, confusion, and meaninglessness that pervade most of everyday life.

Good theoretical science is done by a few dedicated people working alone or with one or two colleagues; this science does not need the large grants that have made prostitutes of most of us, including me. The need to be relevant, the need to be applicable to industry; these are not forces that lead to advances; what leads to advances, often spectacular, is simply the curiosity of the individual scientist, just as Einstein’s curiosity about the structure of space-time led to the theory of relativity. Big science is a driving force for mediocrity.

But I don’t know the answer. Perhaps we can one day return to the times of small individual grants for summer salary and occasional trips to meetings. Perhaps we can return to the times when one’s university salary was tied to quality of research and teaching, rather than to the amount of government support.

In many respects this diatribe is hypocritical, as I have received large amounts of government support, but often there is a dichotomy between what one does and what one believes would be best for society as a whole.

In closing let me thank you so very much for the Timoshenko medal, for your time, and for your interest. THANKS.

Towards A Regularized Dislocation Dynamics

2006-03-10T15:19:00.000-08:00

Professor Wei Cai of Stanford University and his colleagues have recently developed a non-singular continuum theory of dislocation, which could lead to a regulized dislocation dynamics.
One of the major problems of the current dislocation dynamics is its ill conditioning and convergence problem, which is rooted in the continuum dislocation theory itself, because of its singular core. Dr. Wei Cai and his co-workers cleverly uitlize the idea of the Peierls-Nabarro model and extended it to three-dimensional space to formulate a non-singular continuum theory of dislocation, which may lead to a regularized dislocation dynamics.
Their paper is published in a recent issue of Journal of Mechanics and Physics of Solids (Vol. 54, 561-587).

Finite Element Modeling of Polymers

2006-03-09T10:15:00.000-08:00

If you are working on finite element modeling of hyperelastic or viscoplastic behavior of polymers and would like to make user material subroutines for ABAQUS, you may want to look at the following website. It provides lots of very helpful information.

http://polymerfem.com/

TWELVE STEPS TO A WINNING RESEARCH PROPOSAL

2006-03-06T10:40:00.000-08:00

By George A. Hazelrigg, National Science Foundation

I have been an NSF program director for 18 years. During this time, I have personally administered the review of some 3,000 proposals and been involved in the review of perhaps another 10,000. Through this experience, I have come to see that often there are real differences between winning proposals and losing proposals. The differences are clear. Largely, they are not subjective differences or differences of quality; to a large extent, losing proposals are just plain missing elements that are found in winning proposals. Although I have known this for some time, a recent experience reinforced it.

I was having lunch with a young faculty person who had come to NSF to sit on her first proposal review panel. I asked her what she had learned from the process. She quickly rattled off six or eight lessons she could take home. And they were all good lessons. My response was, “Good, just learn from this experience and don’t make the mistakes that the losing proposals made.” You can do the same, and vastly improve your chance of success in proposal writing. Just follow these twelve simple steps.

1. Know yourself: Know your area of expertise, what are your strengths and what are your weaknesses. Play to your strengths, not to your weaknesses. Do not assume that, because you do not understand an area, no one understands it or that there has been no previous research conducted in the area. If you want to get into a new area of research, learn something about the area before you write a proposal. Research previous work. Be a scholar.

2. Know the program from which you seek support: You are responsible for finding the appropriate program for support of your research. Don’t leave this task up to someone else. If you are not absolutely certain which program is appropriate, call the program officer to find out. Never submit a proposal to a program if you are not certain that it is the correct program to support your area of research. Proposals submitted inappropriately to programs may be returned without review, transferred to other programs where they are likely to be declined, or simply trashed in the program to which you submit. In any case, you have wasted your time writing a proposal that has no chance of success from the get-go.

3. Read the program announcement: Programs and special activities have specific goals and specific requirements. If you don’t meet those goals and requirements, you have thrown out your chance of success. Read the announcement for what it says, not for what you want it to say. If your research does not fit easily within the scope of the topic areas outlined, your chance of success is nil.

4. Formulate an appropriate research objective: A research proposal is a proposal to conduct research, not to conduct development or design or some other activity. Research is a methodical process of building upon previous knowledge to derive or discover new knowledge, that is, something that isn’t known before the research is conducted. In formulating a research objective, be sure that it hasn’t been proven impossible (for example, “My research objective is to find a geometric construction to trisect an angle”), that it is doable within a reasonable budget and in a reasonable time, that you can do it, and that it is research, not development.

5. Develop a viable research plan: A viable research plan is a plan to accomplish your research objective that has a non-zero probability of success. The focus of the plan must be to accomplish the research objective. In some cases, it is appropriate to validate your results. In such cases, a valid validation plan should be part of your research plan. If there are potential difficulties lurking in your plan, do not hide from them, but make them clear and, if possible, suggest alternative approaches to achieving your objective. A good research plan lays out step-by-step the approach to accomplishment of the research objective. It does not gloss over difficult areas with statements like, “We will use computers to accomplish this solution.”

6. State your research objective clearly in your proposal: A good research proposal includes a clear statement of the research objective. Early in the proposal is better than later in the proposal. The first sentence of the proposal is a good place. A good first sentence might be, “The research objective of this proposal is...” Do not use the word “develop” in the statement of your research objective. It is, after all, supposed to be a research objective, not a development objective. Many proposals include no statement of the research objective whatsoever. The vast majority of these are not funded. Remember that a research proposal is not a research paper. Do not spend the first 10 pages building up suspense over what is the research objective.

7. Frame your project around the work of others: Remember that research builds on the extant knowledge base, that is, upon the work of others. Be sure to frame your project appropriately, acknowledging the current limits of knowledge and making clear your contribution to the extension of these limits. Be sure that you include references to the extant work of others. Proposals that include references only to the work of the principle investigator stand a negligible probability of success. Also frame your project in terms of its broader impact to the field and to society. Describe the benefit to society if your project is successful. A good statement is, “If successful, the benefits of this research will be...”

8. Grammar and spelling count: Proposals are not graded on grammar. But if the grammar is not perfect, the result is ambiguities left to the reviewer to resolve. Ambiguities make the proposal difficult to read and often impossible to understand, and often result in low ratings. Be sure your grammar is perfect. Also be sure every word is correctly spelled. If the word you want to use is not in the spell checker, consider carefully its use. Not in the spell checker usually means that most people won’t understand it. With only very special exceptions, it is not advisable to use words that are not in the spell checker. Reviewers used to say, “He’s just an engineer. Don’t mind the fact that he can’t spell.” Now they say, “He’s proposing to do complex computer modeling, but he doesn’t know how to use the spell checker...”

9. Format and brevity are important: Do not feel that your proposal is rated based on its weight. Do not do your best to be as verbose as possible, to cover every conceivable detail, to use the smallest permissible fonts, and to get the absolute most out of each sheet of paper. Reviewers hate being challenged to read densely prepared text or to read obtusely prepared matter. Use 12-point fonts, use easily legible fonts, and use generous margins. Take pity on the reviewers. Make your proposal a pleasant reading experience that puts important concepts up front and makes them clear. Use figures appropriately to make and clarify points, but not as filler. Remember, you are writing this proposal to the reviewers, not to yourself. Remember that exceeding page limits or other format criteria, even marginally, can disqualify your proposal from consideration.

10. Know the review process: Know how your proposal will be reviewed before you write it. Proposals that are reviewed by panels must be written to a broader audience than proposals that will be reviewed by mail. Mail review can seek out reviewers with very specific expertise in very narrow disciplines. This is not possible in panels. Know approximately how many proposals will be reviewed with yours and plan not to overburden the reviewers with minutia. Keep in mind that, the more proposals a panel considers, the more difficult it will be for panelists to remember specific details of your proposal. Remember, the main objective here is to write your proposal to get it through the review process successfully. It is not the objective of your proposal to brag about yourself or your research, nor is it the objective to seek to publish your proposal. Again, your proposal is a proposal; it is not a research paper.

11. Proof read your proposal before it is sent: Many proposals are sent out with idiotic mistakes, omissions, and errors of all sorts. NSF program managers have seen proposals come in with research schedules pasted in from other proposals unchanged, with dates referring to the stone age and irrelevant research tasks. Proposals have been submitted with the list of references omitted and with the references not referred to. Proposals have been submitted to the wrong program. Proposals have been submitted with misspellings in the title. These proposals were not successful. Stupid things like this kill a proposal. It is easy to catch them with a simple, but careful, proof reading. Don’t spend six or eight weeks writing a proposal just to kill it with stupid mistakes that are easily prevented.

12. Submit your proposal on time: Duh? Why work for two months on a proposal just to have it disqualified for being late? Remember, fairness dictates that proposal submission rules must apply to everyone. It is not up to the discretion of the program officer to grant you dispensation on deadlines. That would be unfair to everyone else, and it could invalidate the entire competition. Equipment failures, power outages, hurricanes and tornadoes, and even internal problems at your institution are not valid excuses. As adults, you are responsible for getting your proposal in on time. If misfortune befalls you, it’s tough luck. Don’t take chances. Get your proposal in two or three days before the deadline.

These twelve steps are nothing more than common sense. They are so obvious that they hardly bear mention. What is more, they are all necessary conditions. If you fail on any one of these steps, you will reduce your chance of success to practically nothing. Think about it. If you were a reviewer, would you recommend for funding a proposal that doesn’t meet these criteria? So why then do fully half the proposals submitted flagrantly omit them? It’s a fact. Most proposals do not follow these simple steps for success. Therein lies your opportunity. If you take the time to follow these steps, your proposal will be that much better by comparison, and you will vastly increase your chance of success. There is a dark side and a bright side to this. On the dark side, it is not easy to write a good proposal. It takes time and effort to assure that all the above steps are met. Indeed, it can take several months to prepare a good proposal. But, on the bright side, if you do take the time to write good proposals, you will have a much higher success rate, and overall you will spend a much smaller fraction of your life writing proposals. Taking the time to do it right really pays off. There are two more things that you can do to vastly improve your prospects for success as an academic researcher. First, you have to know yourself as well as you can. Who are you ? Where are you going ? Where do you want to go ? I strongly urge people, especially young faculty just starting their careers, to write a strategic plan for their life. Where are you today? Where do you want to be in five years, ten years, and twenty years? Then create a roadmap of how to get from where you are to where you want to be in the future. The focus of this roadmap should be the things over which you have control, and it should acknowledge the things over which you have no control. If you can’t write such a plan, then your goals for the future are not realistic. You can revise the plan as often as you wish. But the fact that the plan exists will influence your proposal in a very positive way, as it will place the research project you propose into the broad context of your life plan. Finally, no matter how much sense the above steps seem to make, everyone retains a bit of skepticism. “Hey, if this guy really knew what he was talking about, wouldn’t he be doing it rather than teaching it?” There is nothing quite like being on the other side of the fence to change your opinion of the process. Volunteer to be a reviewer yourself. It’s easy. Just volunteer. Then you will see how you judge proposals. You will see that your opinions are pretty much identical to the other reviewers, and that you rate proposals pretty much the same as everyone else. Then you will see for yourself that these twelve steps provide nothing more or less than what you would be looking for in someone else’s proposal that you are reviewing.

Researchers Eye Self-assembling Nanotube Networks

2006-03-05T23:49:00.000-08:00

A team from Lawrence Berkeley National Laboratory (LBNL) and University of Kiel (Germany) discovered a process (Physical Review Letter, 96, 086401, [2006]) for forming complex networks of nanotubes in less than a second on a layered crystal, resulting in extensive hexagonal networks, with branches and connections (Read more for details).

Professor Mike Ashby's booklet on "How to Write a Paper"

2006-03-05T16:28:00.000-08:00

pdf download