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Speech of Acceptance of the 1979 Timoshenko Medal by Jerry L. Ericksen

ericksenNew York, 6 December 1979.  First of all, I am flattered and pleased to have the association with the proud name of Timoshenko. Over the years, my respect for him has grown, as I have gained appreciation of how much he did to upgrade the education of mechanics, in engineering. The trend which he helped initiate has continued so that, today, his works seem rather naive and unsophisticated. In part, this is naturally associated with growth on the subject. It might also reflect some good judgment on his part. There are limits to kinds of changes which rather conservative professions will accept. Such need some prodding, if they are to avoid becoming obsolete. Collectively, those of us here represent a kind of activity which we call Applied Mechanics. Like social clubs, it has a kind of formal structure of organization, or we would not be here tonight. At least some like to think of it as more than a club, a profession or some­thing like it. As a profession, it has some responsibility to pinpoint or generate the interesting and important problems, and to find ways to bring to bear the best talent to solve these. Where it fails, the profession will lose ground to another which is more effective. Times have become harder, so we can ill-afford to lose ground, and we should be more aggressive in finding new turf. I would like to reminisce about personal experiences, to illustrate these points.

Particularly, I remember two previous occasions when Ronald Rivlin served to introduce me. One was for a lecture which I gave at an ASME meeting in Atlanta. Afterward, he opined that it would be a good idea if my next performance took the form of mime. Tonight, I shall ignore this sage advice to keep my mouth shut. The other goes back many years, when I was a graduate student in mathematics, at Indiana University. Then, it was not him personally, but his research which was involved. I was not so interested in mathematics, per se, but in what could be done with it. Available courses in continuum mechanics interested me more, but didn't quite fit the bill. During my last year, Clifford Truesdell joined the faculty, and gave a course on general continuum mechanics, covering about what was later published in his now well-known article, "The Mechanical Foundations of Elasticity and Fluid Dynamics". I was excited by Rivlin's imaginative work on rubber elasticity and non-Newtonian fluids, becoming hooked on the subject. I then moved to the Naval Research Laboratory which was, for a time, a center of the activity. It is still pleasant to remember the heated but friendly arguments concerning the foundations of continuum physics, with Rivlin and Richard Toupin, particularly. Imaginative work can induce young people to enter into a field, if they learn of it. Rivlin's work got me involved but, except for Truesdell, I might not have encountered it.

At that time, the Applied Mechanics community was too conservative to be much interested in things so esoteric as the three-dimensional nonlinear theories of elasticity and viscoelasticity, so we made contacts elsewhere.

At the time, practical interest in these subjects was associated mainly with problems arising in the production and use of high polymers. Classical theories of fluids fail to describe the behavior observed in the melts or solutions used to spin synthetic fibers. In the rubbery solids, the deformations of interest are too large to be described by the theories of infinitesimal deformation which were the stock in trade, in Applied Mechanics. In earlier times, the well-known slogan "Better Living Through Chemistry" applied rather well. Most of the research had been done by chemists or chemical engineers, with little training in mechanics. They had real problems, of a complicated nature in mechanics, applied mechanics, in the literal sense. Those in Applied Mechanics might have created a new set of jobs for this establishment; had they been more aggressive. Instead, those primarily involved worked with us. I helped some of them learn about mechanics, and they shared their knowledge with me. As a visiting professor of chemical engineering at Delaware, I gave one of the first courses on general continuum mechanics, for this profession. However, most of the mutual education was accomplished by much less formal means. There were groups outside universities which played an important role in fostering such cooperation, like the Mellon Institute and the Rheology Section at the National Bureau of Standards. Gradually, various universities evolved more formal training programs, helping to bridge the gaps. It has been years since I worked on viscoelasticity theory, but I still communicate with those in polymer rheology, for example. Gradually, such theory has become more accepted in Applied Mechanics, but it would not be fair to say that the center of activity is now here.

I have not lost my love for the nonlinear theories of elasticity and thermoelasticity. I do enjoy the kinds of mathematical problems which they suggest, so it pleases me to see new uses for them. For a long time, it has been recognized that they are useful for the rubbers, and for analyses of typical buckling phenomena. I have become more excited about a different area of application, which is serving to illuminate some misconceptions about such theory. I refer to phase transitions in solids. One type of phenomenon is encountered in a material which you might have used, or seen advertised, the heat-shrink insulation material. Raise the temperature enough, and it shrinks. Similar kinds of things happen in various polymers, also in the so-called memory alloys, like Nitinol. Rather commonly, crystals undergo changes of symmetry, as temperatures change. Presently, we do not know how to properly analyze such effects. When I first began to think about them, I thought that, surely, the answers were to be found in works on classical physics. I soon found that they are not, and that parts of the theory are in a controversial state. Somehow, existing concepts are not quite right, and we need to find proper modifications. I rather like to try my hand at this kind of activity.

Nowadays, we are all familiar with some of the devices employing liquid crystals. There are the digital displays found in watches or small calculators. There are the coasters which evolve pretty color patterns, when a cold drink is set upon them, similar things being encountered in devices sometimes used for non-destructive testing of people, as well as inanimate objects. At first glance, it might seem that it is optics or electronics which is involved, rather than mechanics. Actually, the changes in optical behavior, etc. are associated with changes in orientation. In turn, these are produced by couples. Very roughly, it is similar to bending a wire, by applying couples.

At least in part, I am being honored for my contributions to the theory of these. Thus I will ask you to indulge me, while I recount some more personal history. Shortly after coming to Hopkins, I began to do research on liquid crystals, before I knew that they existed. Studies of the foundations had made clear that remarks about anisotropic fluids in the fluid mechanics literature were based on erroneous concepts. I was teaching a course on continuum mechanics, and thought it would be instructive to present a simple theory of anisotropic fluids, consistent with basic principles, so I did this. It was a theory of structured continua, reminiscent of old theories I had read about in the work of the Cosserats and others. I thought it would be worthwhile in developing a theory of this kind which really worked, for some real material. Chemists are likely to know of good prospects, so I sought advice at an ACS meeting. I was told that my ideas suggested liquid crystals; I had now learned of their existence. I soon became fascinated with their beauty and unusual behavior, soon realized that familiar theories of fluids would not work. Gradually, I plugged away at the theory, to understand how it operated and to make the modifications which seemed to be needed. Almost a decade later, Frank Leslie came to work with me, putting together the final version. Almost immediately, the theory passed its first real test, correctly describing the unusual scaling behavior in Poiseuille flow observed by Fisher and Frederickson. For a long time, this has been an activity in pure science, largely chemistry, but the scene was beginning to change. I had encountered and had fruitful exchanges of ideas with one physicist interested in developing practical devices, James Fergason, then at Westinghouse. Rather suddenly, interest in possible applications perked up, and we began to see more such people. An influential theoretical physicist, Pierre de Gennes, became interested, and formed a very active group at Orsay. We corresponded a bit, about adaptation of theory to cover light scattering. Soon, they were using this to measure viscosities, branching out to cover the other aspects of basic physics, and interesting other physicists. From a selfish point of view, such efforts did much to speed up testing of the continuum theory, which is now well accepted. My original goal was attained, so my interest shifted to other questions. When I began, the basic concept of structured continua, Cosserat continua, or whatever you like to call it, was essentially unused, in Applied Mechanics. In the meantime, a number of others have tried out variations of the idea, on different areas of application, some with success. In liquid crystal research, there is room for those who like the kinds of problems which are encountered in ordinary viscous fluids, to analyze hydrodynamic instabilities, for example. Some such work has been done, mainly by physicists. There are numerous instabilities which occur at very low Reynold numbers, having no counterpart in ordinary fluids. Some have been analyzed fairly well. There are very detailed measurements, motion pictures, etc. of others, not yet analyzed. Liquid crystal research is beginning to overlap polymer research, in an important way. Highly oriented polymer fibers, of exceptionally high strength, are now being made and used commercially. These are spun from a liquid, a polymer solution. The trick is to prepare this so it is already well oriented. Qualitatively, this is, in effect, a liquid crystal. Some of the available data indicates that the theory will have to be modified somewhat, to cover these newer fluids, but we can make good use of some of the experience acquired, and the polymer workers are pursuing this.

My experiences suggest that Applied Mechanics has had two quite different meanings. First, it has served as a name for a kind of profession having rather narrow and fixed limits. Viscoelastic fluids do not belong in Fluid Mechanics, you know. As a young man, I found this kind of attitude too stodgy for me, and I still do. Second, we encounter numerous applications of mechanics to real problems. If the profession is too reluctant to provide expert help with these, it does not deserve the name; it is in fact a private club. In easy times, the profession might survive, but the last several years have not been so easy, and territory has been lost to other professions. Call the predators vultures, if you will, but ask whether a vulture prefers to attack healthy, vigorous prey.

In Mechanics, the scene is changing in other ways, at least partly because of economic pressures. Some see the whole subject shifting, to become much more concerned with immediate applications. I think that it may become both more and less applied at the same time, which is what I would prefer. As the mathematician or other pure scientist shifts, he may come in on the least applied end, and I see this happening. My experience in liquid crystal research, as well as polymer mechanics indicates that more real progress is made when people with diverse backgrounds mingle, stimulated by mutual interest in some problem. Nearest neighbors tend to think alike, to get stuck in a rut which might now be comfortable, but is headed into quicksand. As a group, we in Mechanics seem to have a reputation for being intolerant of those who do not see eye-to-eye with us. He who is stung by this will be glad to see us disappear into the mire. Perhaps it is wishful thinking, but I believe that we are changing for the better, on the whole.

I see more professionals venturing outside the stockade, finding the experience rewarding, and making contributions, in area quite different from those which I have mentioned. We still need to do more to help the best minds tackle the best problems. Fields start to move because someone gets a novel idea or technique, and others see ramifications which appear to be attractive. It is my own view that our own interests are best served by doing whatever we can to promote the best research. I do not know what can be done to create more of the spark plugs, but we can be alert for ways to help those which are firing. It is quite feasible to assess the talents of some bright young man, helping them to find the right plugs. It requires that we have some contact with them, and I would be happier if there were more such contacts. Like some of you, I have been thinking about and experimenting with ways to improve these situations. Perhaps, this is the time, but not the place, to assess the value of the efforts.

There comes a time when a speaker enthusiasm for talk must give way to concern for the listener's weary bottoms. Thank you for listening to my ramblings.

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Zhigang Suo's picture

The following emails record the sequence of events.  Michael Suo scanned the original text, and converted it into a Word file.  The HTML file posted here is identical to the original text, except for the correction of several typos.  Ericksen's Autobiography is available in "Mechanics and Mathematics of Crystals:  Selected Papers of J.L. Ericksen", editted by M.F. Beatty, J.L. Ericksen, M.A. Hayes.  Your may also read the Autobiography online at Google Books.

from Jerry Ericksen
to suo@seas.harvard.edu
date Mon, Jun 6, 2011 at 12:32 PM

Dear Prof. Suo,
I was the 1979 recipient of the Timoshenko medal. Some time ago, someone asked me for a copy of my acceptance speech. At the time, I could not find this. In going through some old files, I just found it. I will be glad to mail a copy, if you can send me an address.
Best Wishes,
Jerry Ericksen

 

from Richard D. James james@aem.umn.edu
to Zhigang Suo <suo@seas.harvard.edu>
date Sun, Nov 8, 2009 at 2:06 PM
subject [Fwd: Re: [Fwd: Jerald L. Ericksen's speech upon accepting the Timoshenko Medal]]

Dear Zhigang,  Too bad, no luck, see below.  I enjoyed seeing you in Vancouver and thanks for inviting me.  I'll always remember: a picture is worth 1000 words, but an equation is worth 1000 pictures!
Rick
--

Richard D. James
Russell J. Penrose Professor
Department of
Aerospace Engineering and Mechanics
University of Minnesota

Minneapolis,  MN  55455
tel. (612) 625-0706
fax  (612) 626-1558

james@umn.edu

Dear Dick,

Sorry, but I no longer have a copy of the Timoshenko speech. We are enjoying (?) winter storms, lots of rain here and snow piling up in the mountains.

Best Wishes,

Jerry

On Nov 8, 2009, at 10:04 AM, Richard D. James wrote:

Dear Jerry, I got a request, below, from Zhigang Suo for the text of your speech for the Timoshenko Medal. I wonder if you still have this? They would like to post it on the imechanica website, which has become quite popular. Some of the other ones are already posted, see http://imechanica.org/node/177

A late Indian summer here in Minneapolis.

Best wishes, Dick

from  zhigang suo suo@seas.harvard.edu
to  Rick James
<james@umn.edu>
date  Sat, Nov 7, 2009 at 6:18 PM
subject  Jerald L. Ericksen's speech upon accepting the Timoshenko Medal

Dear Rick: 
It was delightful to talk to you in Vancouver.  We talked about locating Jerald L. Ericksen's speech upon accepting the Timoshenko Medal.  It would be wonderful if you could ask him for it.  I have tried with ASME, and they don't have a file on record.  We would love to post it on iMechanica, along with the speeches of other medalists.  See http://imechanica.org/node/177
Thank you.
Zhigang

Dear Prof. Suo,

Thank you so much for these Timoshenko lectures. What a great deal of benefit it has done for young people like me. It has given a rich perspective into the field of Mechanics. These lectures have brought alive the giants in the field, and the feeling while reading them, is as if one were present during the ceremony itself. One cannnot hope to meet most of these greats during this lifetime, but atleast through these lectures, one gets to know their rich experience which is for us to revel and ponder upon.

Waiting for Prof. Needleman's speech... 

Thank you very much!

Vineet Nair 

 

Zhigang Suo's picture

Dear Vineet:  Many thanks for the kind words.  You may also wish to read Ericksen's Autobiography, published in "Mechanics and Mathematics of
Crystals:  Selected Papers of J.L. Ericksen", editted by M.F. Beatty,
J.L. Ericksen, M.A. Hayes.  The full text of the autobiography is free online.

Many thanks for the suggestion. Infact, I had read certain parts of his autibiography some time back from the same book. I was quite eager to learn about him and his work. Furthermore, my masters advisor (Dr. Chakradhar Iyyunni) is the doctoral student of Prof. Yi chao Chen, who as we all know, is Prof. Ericksen's doctoral student.

I think, Prof. Ericksen's and Prof. Rivlin's autobiographical accounts are two very good sources that give an account of the early years of the nonlinear continuum mechanics and its subsequent development. Ofcourse, they also lay bare certain disagreements among people involved, in their approach towards to doing mechanics. But I guess, as in any other field of endeavour, disagreements are welcome, more so when they are based upon facts. For then, the search for the truth becomes all the more exciting, fulfilling and a rewarding exercise.

Thank you once again,
Vineet Nair

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