Applied Mechanics Research and Researchers

We are migrating to iMechanica.Org

noreply@blogger.com (Zhigang Suo) — Sat, 09 Sep 2006 16:24:00 +0000

Making Sense of the Web's Structure

noreply@blogger.com (Shaofan Li) — Fri, 08 Sep 2006 17:52:00 +0000

Scientists in Britain report baldness breakthrough

noreply@blogger.com (Shaofan Li) — Sun, 03 Sep 2006 21:51:00 +0000

Should anyone write a Wiki textbook on Mechanics of Materials ?

noreply@blogger.com (Shaofan Li) — Sat, 02 Sep 2006 17:48:00 +0000

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

noreply@blogger.com (Shaofan Li) — Sat, 02 Sep 2006 17:40:00 +0000

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

noreply@blogger.com (Xiaodong Li) — Wed, 30 Aug 2006 00:12:00 +0000

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

noreply@blogger.com (Rui Huang) — Tue, 29 Aug 2006 18:44:00 +0000

The drama of a mathematical proof

noreply@blogger.com (Zhigang Suo) — Sat, 26 Aug 2006 22:03:00 +0000

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

noreply@blogger.com (Shaofan Li) — Tue, 15 Aug 2006 14:00:00 +0000

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

noreply@blogger.com (Shaofan Li) — Tue, 15 Aug 2006 13:58:00 +0000

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)

noreply@blogger.com (Shaofan Li) — Tue, 15 Aug 2006 13:56:00 +0000

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

noreply@blogger.com (Shaofan Li) — Sat, 12 Aug 2006 23:40:00 +0000

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)

noreply@blogger.com (Shaofan Li) — Wed, 09 Aug 2006 03:24:00 +0000

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

noreply@blogger.com (John D) — Thu, 03 Aug 2006 22:53:00 +0000

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

noreply@blogger.com (Shaofan Li) — Fri, 28 Jul 2006 22:33:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Mon, 17 Jul 2006 17:23:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Thu, 13 Jul 2006 15:06:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Tue, 11 Jul 2006 01:56:00 +0000

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

noreply@blogger.com (Shaofan Li) — Sun, 09 Jul 2006 06:02:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Sat, 08 Jul 2006 20:48:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Sat, 08 Jul 2006 12:59:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Sat, 01 Jul 2006 12:49:00 +0000

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

noreply@blogger.com (Xiaodong Li) — Wed, 28 Jun 2006 18:06:00 +0000

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

noreply@blogger.com (Zhigang Suo) — Sat, 24 Jun 2006 13:59:00 +0000

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

noreply@blogger.com (Shaofan Li) — Tue, 20 Jun 2006 23:31:00 +0000

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 ...)