Saturday, July 08, 2006

1990 Timoshenko Medal Lecture by Stephen H. Crandall

The Joy of Applying Mechanics

Stephen H. Crandall, Massachusetts Institute of Technology

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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