Thursday, March 30, 2006

Review articles on Flexible Electronics


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

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

Tuesday, March 28, 2006

Learning from the dragonfly to engineer better flight

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

Friday, March 24, 2006

1996 Timoshenko Medal Lecture by J. TINSLEY ODEN

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.

Thursday, March 23, 2006

The MacTutor History of Mathematics archive

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

Tuesday, March 21, 2006

Response/Feedback requested: Journal Club?

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.

Monday, March 20, 2006

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

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.

Sunday, March 19, 2006

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

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

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!

Saturday, March 18, 2006

2006 Gordon Research Conference

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

Bernard Budiansky (1925 - 1999)

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...

Friday, March 17, 2006

Journal of Mechanics of Materials and Structures

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.

Wednesday, March 15, 2006

Cosmic 'DNA': Double Helix Spotted in Space

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

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

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

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.

Tuesday, March 14, 2006

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

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.

Friday, March 10, 2006

2004 Timoshenko Medal Lecture by Morton E. Gurtin

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

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).

Thursday, March 09, 2006

Finite Element Modeling of Polymers

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/

Monday, March 06, 2006

TWELVE STEPS TO A WINNING RESEARCH PROPOSAL

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.

Sunday, March 05, 2006

Researchers Eye Self-assembling Nanotube Networks

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"

pdf download

Researcher Spotlight: Professor Lambert Ben Freund (LBF)

Notes of AMR Administrators: This article is an adapation of a biography that appeared in the Journal of Mechanics and Physics of Solids, 51, (2003), the proceedings of a symposium, held at Caltech and organized by Ares Rosakis, G. Ravichandran and Subra Suresh, on the occasion of the 60th birthday of Professor L.B. Freund.


Lambert Ben Freund (LBF) was born on November 23, 1942, in Johnsburg, Illinois, a tiny rural community of a few hundred people in the northeast corner of the state. This part of the Midwest was opened to European settlement by the Black Hawk War of the 1830s. A small delegation of his ancestors arrived in the area in 1841. The enthusiastic letters they wrote to relatives waiting in Bavaria and the Rhineland resulted in rapid settlement of the area by immigrant families in the mid-1800s. The farm that would become the Freund family farm was deeded to one of the settlers through an 1820 Act of Congress for the sale of public lands by the government. It was subsequently purchased by LBF's great-grandfather who passed on one quarter section (160 acres) to each of four sons, one of whom was LBF's grandfather. The land was then passed on to the only surviving son, Bernard Freund. The third of four children, LBF was raised by his parents, Bernard and Anita Freund, on the family dairy farm. The responsibilities for managing a dairy farm took precedence over social activities and school sports. At the same time, it provided a vigorous outdoor life with exposure to the cycles of nature, the art of breeding livestock and an appreciation for the value of hard work. He attended St. John the Baptist Elementary School and the McHenry Consolidated High School where he demonstrated a talent for mathematics and science.

Upon graduation from secondary school, LBF followed the advice of his father to continue his education in order to qualify for a good job. In 1960, he enrolled at the University of Illinois at Urbana-Champaign in order to study electrical engineering. The standard curriculum of the day included a required course on statics and dynamics, taught in the Department of Theoretical and Applied Mechanics, in the second year. Through this course, he discovered a natural interest and appreciation for the field of mechanics. Consequently, he changed his major area of study to a relatively new program at the U. of I. in Engineering Mechanics. In addition to broad exposure to the branches of mechanics, the program offered the opportunity to study to some depth in mathematics. The program also required a sequence of courses in the practice of engineering and, to fulfill the latter objective, he followed the sequence of courses in machine design in the Department of Mechanical Engineering. The mechanics program also required a senior thesis, and this turned out to be an entirely experimental project on creep rate acceleration in lead subjected to cyclic loading. The experience of experimental work and study of machine design proved to be useful in the course of four summers and university holidays spent in the research and development division of the Frank G. Hough Co. of Libertyville, Illinois, manufacturer of rubber tired earth moving equipment. This practical work experience provided the opportunity to do experimental instrumentation, data reduction from field testing and management of testing programs to certify new designs of transmission clutches or axles, for example. In the course of this work, he also learned the rudiments of operating heavy equipment.

LBF receive the Bachelor of Science and Engineering Mechanics in 1964 from the University of Illinois. In order to become eligible for more attractive professional opportunities in engineering, he decided to continue his studies toward a master's degree at the same institution. It was during this period that graduate courses on energy methods in applied mechanics and wave motion provided the inspiration to pursue the subject of mechanics much more deeply. In 1965, he enrolled in the program in theoretical and applied mechanics within the Department of Civil Engineering at Northwestern University as a National Defense Education Act fellow. Many fellowships of this kind had been created in response to the launching of the Sputnik satellite in 1957 by the Soviet Union. He was assigned to work with a relatively new faculty member at Northwestern, Professor Jan D. Achenbach, who proved to be a superb research advisor. The association was productive and it resulted in a lifelong professional friendship.

While an undergraduate at the University of Illinois, LBF was introduced to Colleen Hehl, an undergraduate art student at Illinois State University in Normal, Illinois, by a mutual friend. Following completion of his master's degree at Illinois and her bachelor's degree at Illinois State, LBF and Colleen were married in 1965. As they began their new life together in Evanston, Illinois, Colleen taught art in secondary school in Wheeling, Illinois, while LBF pursued his graduate study at Northwestern. He also participated actively on the Civil Engineering intramural basketball team.

LBF finished his Ph.D. research at Northwestern in less than two years, with a thesis entitled Diffraction of Elastic Waves by Semi-Infinite Plane Barriers at the Interface of Elastic Media. Based on the advice of faculty members at Northwestern, LBF decided to pursue postdoctoral research in order to gain exposure to branches of mechanics not included in his graduate education. In 1967, an opportunity for relatively unrestricted research became available within the Materials Research Laboratory at Brown University, and he elected to pursue that possibility without hesitation. The position offered the opportunity to study plasticity and the mechanics of large deformation phenomena. In 1969, he was invited to join the regular faculty as Assistant Professor in the Division of Engineering at Brown University.

The year 1969 also marked a major change in the personal lives of LBF and his wife Colleen, namely, the birth of their first son, Jonathan. Thereafter, family became a central focus for them, a perspective that provided strength and motivation throughout their lives. The family expanded again four years later with the birth of twin sons, Jeffrey and Stephen, in 1973.

By 1970, the research area of dynamic fracture mechanics was emerging throughout the international research community. By this time, Elizabeth Yoffe in the United Kingdom and Bertram Broberg in Sweden had publish their pioneering mathematical solutions of problems in fracture dynamics, and others were beginning to devote their attention to the subject. Significant work was produced at a time by J. D. Eshelby, Jan Achenbach and others. With research funding provided by The Office of Naval Research and the National Science Foundation, LBF undertook a program of research focused on several fundamental issues in the area of fracture dynamics. The field was given major impetus by a series of his papers, published in the Journal of the Mechanics and Physics of Solids between 1972 and 1974. This work provided, for the first time, a complete mechanics of elastodynamic crack growth that could be applied without a priori assumptions on the nature of that growth. Through that work, equations of motion for growth of tensile and shear fractures became available for interpretation of laboratory experiments and field failures. The work stimulated an international research effort focused on the study of fracture initiation, crack propagation and crack arrest under dynamic conditions. Over the next 30 years, this work and its consequences inspired a number of breakthroughs in both theory and experiment and it broadened the scope of fracture mechanics through the active involvement of his former students, postdoctoral researchers and other coworkers.

In addition to his fundamental scientific contributions to dynamic fracture mechanics, LBF's work has had a profound impact on a broad range of other areas within the area of fracture mechanics. On the side of practical applications, his work on elastic-plastic fracture of pipelines and pressure vessels contributed to the understanding of failures in practice, the interpretation of field experiments intended to improve the quality of pipelines steels, the design of mechanical crack arresters for buried pipelines and the design and interpretation of laboratory experiments on characterizing the dynamic fracture behavior of engineering materials. More recently, he has pursued an understanding of the observed fragmentation of ductile materials when deformed at very high rates. Explanation of this phenomenon had remained an open problem in the field for half a century until it was resolved through its treatment as a dynamic plastic bifurcation phenomenon by LBF and postdoctoral associates Vijay Shenoy and Pradeep Guduru. His work has also shown how the addition of a relatively soft, light-weight material to the surface of a ductile structural material can have a marked effect in suppressing the onset of ductile fracture.

In the areas of seismology and seismic source modeling within geophysics, LBF's work on dynamic shear provided timely quantitative guidance toward the understanding of the ruptures in the crust of the earth that give rise to earthquakes. In particular, his prophetic papers on intersonic shear rupture examined the theoretical possibility of such highly dynamic scenarios. Thirty years later, laboratory experiments and geophysical field evidence verified his theoretical predictions to a surprising degree of accuracy through the work of his former student Ares Rosakis and others. His contributions on dynamic failure of materials culminated with publication of a monograph by Cambridge University Press in 1990. This book, entitled Dynamic Fracture Mechanics, continues to be the major reference on the subject, not only within the engineering sciences but also in other branches of physical science which have developed an interest in dynamic fracture phenomena.

While still deeply involved in work on dynamic fracture, LBF became interested in the subject of deformation and failure of thin film materials. He began his pursuit of this area, which was new not only to him but to the mechanics community, with the characteristic enthusiasm and rigor that has governed his entire research career. Indeed, for the years that followed much of his research effort was devoted to various aspects of thin-film research. His work in the area began with development of an understanding at a basic mechanistic level of the nucleation, propagation and blocking of threading dislocations in thin films. His series of papers on the subject forms the foundation of understanding the micromechanics governing this complex phenomenon which is crucial to the fabrication of high quality semiconductor films for microelectronic devices. His research further led to the study of diffusion assisted roughness evolution on film surfaces and on the analysis of morphology evolution of semiconductor islands, or quantum dots, during deposition under high vacuum conditions. He also provided insights into the failure of thin-film conducting materials, particularly through the modeling of void nucleation and stress-driven void growth in passivated interconnect lines in microelectronic devices and the modeling of electromigration failure of conducting lines.

LBF and his students provided the first integration of quantum mechanics into mechanical deformation to assess the role of residual strain fields on charge carrier transport in quantum devices. This work, which evolved in parallel with an experimental study of the problem at Brown University, added a new dimension to the field of mechanics and has inspired a number of young people to pursue similar studies spanning the domains of traditional mechanics and modern electronics. In very recent work, LBF and Vivek Shenoy have established a connection between surface energy of small single crystals of semiconductor materials and mechanical strain that arises naturally in the fabrication of small semiconductor heterostructures. This discovery has provided the means to understand experimental observations that defied interpretation for years, particularly the persistence of the surface orientations not regarded as low-energy orientations. The stabilization of these surface orientations is due solely to mechanical strain. In addition, through this study, a new variational approach for analyzing the evolution of surfaces of small strain structures in during their formation was introduced. The new methodology provides an effective and efficient way to analyze these systems.

This body of work, spanning the scale from wafer curvature methods for stress measurement, through fracture and buckling of stressed thin films, down to surface phenomena on the nanoscale, was summarized in a book entitled Thin Film Materials, co-authored with Subra Suresh of the Massachusetts Institute of Technology and published by Cambridge University Press in 2003.

Although a significant number of LBF's research papers have been solely authored, he has also pursued productive collaborations with many graduate students, postdoctoral researchers, Brown University colleagues and colleagues at other institutions. He has spent sabbatical/research leaves at Stanford University (1974-75 and again in 1995), Harvard University (1983-84), California Institute of Technology (1988, 1999 and again in 2003), University of California at Berkeley (1995) and the University of Illinois (2003).

LBF's impact on the engineering sciences has been significant and permanent. He has served as the nucleus for the evolution of new fields and as a source of inspiration for an entire generation of scientists and engineers. While these new areas of research have sustained a life of their own outside of his direct involvement, LBF has continued to find new ways to use his sense of opportunity and need to shape the field of mechanics for the future. He is currently cultivating an interest in the adhesion of biological materials and the generation of intermolecular interaction forces related to such processes. Among the goals of work in this area is to understand cell motility in biological functions and, further, to develop strategies for modifying that motility.

LBF has taken seriously his responsibilities as teacher and mentor throughout his career. His lecturing skills and classroom presentations are legendary among Brown graduates. The clarity and transparency of underlying thought processes, as well as an acute sense of organization of course material, makes his teaching style an experience to remember.

In addition to being an accomplished teacher and researcher, LBF has another side to his professional persona that is devoted to the service of the community. He has served as chairman of the Division of Engineering at Brown University, as Treasurer of the International Union of Theoretical and Applied Mechanics (IUTAM), currently as President of IUTAM and as Chairman of the Applied Mechanics Division of the American Society of Mechanical Engineers (ASME). He has also had long and successful tenures as technical editor of the Journal of Applied Mechanics, as coeditor (with John Willis) of the Journal of the Mechanics and Physics of Solids, and as associate editor of the Proceedings of the National Academy of Sciences. Service in these positions reflects a desire to foster a high standard for the field, to guide the development of younger researchers, and to encourage broad interaction within the engineering and scientific communities. Aptly recognized for his contributions by many professional societies, LBF has been the recipient of a number of principal awards in the field, including the George R. Irwin Medal (American Society for Testing and Materials), the William Prager Medal (Society of Engineering Science) and the Stephen P. Timoshenko Medal (American Society of Mechanical Engineers). He has also been elected to membership in the American Academy of Arts and Sciences (1993), the National Academy of Engineering (1994) and the National Academy of Sciences (1997).

LBF has pursued a number of interests beyond scholarly and professional activities. He has found relaxation in playing the guitar since his undergraduate student days, an interest that has been passed on to his eldest son. He enjoys a large collection of recorded music containing mostly baroque and classical works of the Masters of those periods, as well as a selection of blues and American folk music. He is an avid reader with particular interests in biography and American history, particularly the eras of the US Civil War and World War II. He is a lifelong admirer of Abraham Lincoln and an interested student of Lincoln's published speeches and correspondence.

At the time of this writing, LBF and Colleen, his spouse of more than 40 years, reside in Barrington, Rhode Island. Their family continues to be a focal point in their lives. The eldest son Jonathan is a professor of mechanical and aeronautical engineering at the University of Illinois; he and his wife Amy have contributed four grandchildren to the family. Jeffrey is the cofounder and chief technology officer of the small company Clickability, based in San Francisco and a developer of Internet software; he and his wife Megan will be contributing a grandchild of their own to the family in the near future. Jeffrey's twin brother Stephen is a professor of computer science at Williams College in Massachusetts.