Downloaded from rsbm.royalsocietypublishing.org on December 26.2010 STEPHEN PROKOFIEVITCH TIMOSHENKO 1878-1972 Elected For.Mem.R.S.1944 BY E.H.MANSFIELD,F.R.S.AND D.H.YOUNG INTRODUCTION STEPHEN PROKOFIEVITCH TIMOSHENKO will long be remembered as an out- standing scientist,distinguished engineer,and a great and inspiring teacher. His long and active career extended from Czarist Russia,across Europe,and finally to America.The events of his interesting and often exciting life can be read in his most delightfully written autobiography,As I remember. Throughout his career,Timoshenko held steadfastly to one goal.This was to further the advancement of mechanics as a science and to promote its application to practical engineering problems.He strove always to bring mathematical theory and engineering practice into closer harmony.In attaining this goal he had singular success.His scientific papers,which taken collectively represent a monumental contribution to applied mechanics,were always aimed at solving real problems.His world-famous engineering textbooks put the most recent theoretical results into usable form for practising engineers.As a teacher,he was able to pass on to his students not only knowledge but much of his enthusiasm for mechanics.He was much loved and admired by all of his students and can never be forgotten by those who were fortunate enough to come under his influence. Stephen Timoshenko really had two careers:one in Russia before the Revolution and one in America after the first world war.Each of these careers divides itself rather naturally into three periods.The first period in Russia, representing his early childhood and formal education,begins with his birth in 1878 and ends with his graduation from the Institute of Engineers of Ways of Communication in St Petersburg in 1901.The second,representing his early years as a professor,his graduate study in Germany and the beginnings of his creative scientific work,ended abruptly with dismissal from his university post for political reasons in 1911.The third,covering the years from 1911 to 1922, represent the impact of the Revolution on his life.They represented for him and his family a period of great uncertainty and danger during which they wandered all over Russia,then into Western Europe,and finally to America. 679 The Royal Society is collaborating with JSTOR to digitize,preserve,and extend access to Biographical Memoirs of Fellows of the Royal Society. www.jstor.org
The Royal Society is collaborating with JSTOR to digitize, preserve, and extend access to Biographical Memoirs of Fellows of the Royal Society. www.jstor.org ® Downloaded from rsbm.royalsocietypublishing.org on December 26, 2010
Downloaded from rsbm.royalsocietypublishing.org on December 26.2010 盒A✉A 5.]万mo-hmk和
Downloaded from rsbm.royalsocietypublishing.org on December 26, 2010
Downloaded from rsbm.royalsocietypublishing.org on December 26,2010 680 Biographical Memoirs The first period in America finds Timoshenko in the role of research engineer, first in Philadelphia and then with the Westinghouse Company in Pittsburgh. This period extended from 1922 to 1928.The second period (1928-36)consti- tutes his eight years at the University of Michigan and marks his return to academic life.Without doubt,these years represent the high point of his impact on American engineering education.The third period,which he spent at Stanford University,was the longest in his life.It extended from 1936 until 1965,at which time he returned to Europe to live with his daughter in West Germany.Except for summer trips to Switzerland and one to Russia,he remained there until his death on 29 May 1972,at the age of 93. THE RUSSIAN YEARS Period of formal education Stephen Timoshenko was born in the village of Shpotovka in Konotop County of Ukrainia on 23 December 1878.After early education at home, he entered the real-gymnasium in the town of Romni in 1889 and graduated in 1896 at the age of 18.He had prepared himself well for the competitive entrance examination to the Institute of Engineers of Ways of Communication and was admitted to this school in September 1896.Here he began his studies to become a railway structural engineer,a dream that he had held since early childhood.However,a trip to the International Exposition in Paris during the summer of 1900 convinced him that there were many new and more interesting subjects than railroads to be studied.In the section devoted to engineering structures were exhibited many models of different bridges,roofs, canals and harbour installations.Of particular interest to Timoshenko was a model of the big arch viaduct over the river Viaur near the town of Carmoux. This viaduct,which incorporated the biggest cantilever arch in the world,was in the process of being built and Timoshenko resolved to go and see it.He spent a fascinating three weeks at the site where the construction was under the supervision of a Monsieur Compagnon who had previously supervised the construction of the Eiffel Tower.On his return to the Institute a further year of studies was necessary before graduating in 1901.This was followed by a year of compulsory military training before Timoshenko was ready to start his professional career as a research worker and teacher of applied mechanics. In August 1902 Timoshenko married Alexandra Archangelskaya,a final-year medical school student whom he had known since his student days.They managed to make ends meet by renting a three-roomed apartment which they shared with Timoshenko's brothers. Period of scientific work Timoshenko's first job was that of laboratory instructor at the Institute's Mechanics Laboratory,which he began in the autumn of 1902 and for which he was paid 100 roubles per month.His duties consisted of making extensive experimental studies of strength of rails,structural steel and cement.He
Downloaded from rsbm.royalsocietypublishing.org on December 26, 2010
Downloaded from rsbm.royalsocietypublishing.org on December 26,2010 Stephen Prokofievitch Timoshenko 681 realized that to make progress in his chosen field he would require a greater knowledge of mathematics,but the mathematics courses available were of an abstract nature totally divorced from the realms of engineering application. It was A.N.Krylov who pointed out to Timoshenko that the engineer had to study the old books rather than the new in mathematics.The following year, he obtained an instructorship at the newly organized St Petersburg Polytechnical Institute.The years 1903 to 1906 which he spent there mark the beginning of Timoshenko's creative scientific work in the direction of utilizing mathematics to solve engineering problems.His summers were spent in Germany,where he studied under such men as August Foppl,Ludwig Prandtl and Felix Klein. After his return from Germany in 1904,he wrote his first paper on the subject of Various strength theories.Following this,in the spring of 1905,he published a paper On the phenomenon of resonance in shafts.This work took into account the effect of the distributed mass of the shaft which had never before been considered.It showed the influence on Timoshenko of Lord Rayleigh's books, Theory of sound,and represents the first time that Rayleigh's method'was applied to an engineering problem.His earlier interest in the theories of strength of materials led him naturally to study the theory of elasticity and,in particular, the book by A.E.H.Love.Not knowing the English language he spent several months translating Love's book with the aid of a dictionary,working at it for two hours a day.He soon acquired sufficient working knowledge of the language to enable him to understand the technical literature. In 1905,Timoshenko began work on lateral buckling of I-beams under Prandtl's direction in Germany.He soon found that in order to approach the problem of buckling,he had to know something about the torsion of an I-beam Obviously,the Saint-Venant theory of torsion was not applicable and he had to develop something new.He says that it took him about two weeks to figure out that instead of the usual torsion equation T=CΦ' he had to develop the equation T=CΦ'-DΦ where D is a constant depending on the bending rigidity of the flanges and the distance between them.This was the beginning of the concept of the warping constant used today in the discussion of torsion of prismatic bars of thin-walled open cross section. Timoshenko again went to Germany in the summer of 1906 and on this occasion he began some work on the buckling of plates.He was acquainted with the work of Bryan,who had found critical values of compressive stresses by strain energy considerations.Timoshenko,working directly with the differ- ential equation for the deflexion of the plate,succeeded in establishing critical values of the compressive stress from the boundary conditions.A paper describing this work was published in the spring of 1907.In later years,the tables and diagrams presented in this paper were widely used by ship-builders and by aircraft designers.Several other papers dealing with stability problems
Downloaded from rsbm.royalsocietypublishing.org on December 26, 2010
Downloaded from rsbm.royalsocietypublishing.org on December 26,2010 682 Biographical Memoirs followed in rapid succession,and this may well be regarded as one of the most productive periods in his career. All these investigations on elastic stability showed that only the simplest cases could be solved rigorously.This led Timoshenko to develop an approxi- mate method of solution based on a comparison of strain energies of a system in its initial and buckled shapes.The method was similar to that used by Rayleigh for approximate calculations of frequencies of natural vibration and again shows the influence of Rayleigh's book on Timoshenko's work.This was the first time that the so-called Rayleigh-Ritz method'had been applied to problems in the field of stability.This ability to see that certain ideas developed for work in one area could be transferred to another and made to yield rich results was characteristic of many of Timoshenko's contributions.The results of this work won Timoshenko the Jourawsky prize,awarded once every ten years for the best paper on structural mechanics.It was later translated into French and published in the Annales des Ponts et Chaussees in 1913.It had great influence on further developments in the field of elastic stability. In 1906,when he was only 28 years old,Timoshenko took part in the open competition for a professorship at Kiev Polytechnic.He received word in November that he had been selected to the professorship in strength of materials. He began his lectures in this subject in January 1907.It was at this time that he developed the technique of beginning a course with a discussion of the simplest cases and only gradually building up to full generalizations.This was contrary to the customary procedure of beginning with a general discussion of stress and strain in three dimensions and gradually working down to=P/A. It proved so successful that in subsequent years of teaching he always used this approach in his classes;it was much appreciated by students.After developing the course in strength of materials,Timoshenko expanded his notes into a textbook on the subject,which first appeared in 1911.This was the first of his many textbooks on applied mechanics. In addition to the work on the application of energy methods to stability problems already discussed,Timoshenko also developed at.this time some valuable applications of normal coordinates to the solution of problems of bending of beams and plates.This was also extended to cases of combined bending and compression or tension and to forced vibrations of beams.This work is described in a paper,Etude de la flexion des barres,Annales des Travaux de Belgigue,1914,and another,Erzwungene Schwingungen prismatischer Stabe,Zeitschrift fur Mathematik und Physik,1911. In 1909,Timoshenko was elected dean of the civil engineering school at Kiev Polytechnic.This promotion to administrative levels not only interfered with his teaching and scientific work but was also the forerunner of serious trouble for him.There had been considerable political unrest and student demonstra- tions some six years earlier which had necessitated the closure of all institutions of higher learning for several months.The institutions were reopened in the autumn of 1906 after various revolutionary demands had been met;these including the granting of a constitution,the convocation of a State Duma and a
Downloaded from rsbm.royalsocietypublishing.org on December 26, 2010