Edward Walter Hart, a theoretical and experimental physicist who was well known for developing the universal equation of state for mechanical deformation of solids, died on 22 December 2004 in Lancaster, Pennsylvania.
Born in Easton, Pennsylvania, on 14 January 1918, Ed graduated from the City College of New York in 1938 and then received MS and PhD degrees from the University of California, Berkeley. During World War II, he worked for the US Navy in Washington, DC, where he invented magnetic compass correctors and a better ship compass—work for which he received a Meritorious Civilian Award. He next spent 25 years at the General Electric Research and Development Laboratory in Schenectady, New York, before becoming a joint professor in the materials science and engineering department and in the theoretical and applied mechanics department at Cornell University in 1976. His research years at Cornell, from 1976 to 1988 when he became emeritus, were particularly productive.
Ed invested four decades of research on micromechanics of materials and, specifically, on the microscopic nature of failure and inelasticity. Beginning with his early research in 1952 on state-variable modeling of inelastic deformation, a tremendous amount of effort has been invested in linking a material’s microstructure (including grain-boundary and dislocation motion) and its mechanical properties. He is rightfully famous for his theoretical work in the modeling of inelasticity, fracture, precipitation hardening, dislocation motion, self-diffusion, grain-boundary motion, and the mechanics of superplasticity.
The typical senior-level textbook on the mechanical properties of materials has a detailed section on the generalized equation of state, which can be obtained from a tension test and then applied to plastic deformation processes for all time-independent combinations of stress and strain. The last two decades of Ed’s work were dedicated to adding time dependence to the equation-of-state approach. The input again was the tension test, but Ed added time as a variable along with the results from stress-relaxation tests at points of fixed generalized strain. His highly cited 1967 Acta Metallica paper “Theory of the Tensile Test” and numerous papers on load relaxation and creep led to a generalized time-dependent equation of state that could be obtained from experiments. A complement and challenge to those theorists who attempt to use atomic terms to describe point defects, dislocations, planar defects, second phase particles, and so on, the universal equation of state has led to enormous elucidation of time-dependent inelastic and permanent deformation. Ed was awarded an Alexander von Humboldt Senior Scientist Award by West Germany in 1982.
Ed was a Renaissance man. As a young man, he studied composition under Aaron Copland. He played guitar, viola, and piano and directed a choir and a chorus. He studied modern dance with Welland Lathrop, and he was a founder of the Schenectady Civic Ballet Co and served as its president from 1960 to 1963. A lover of nature, mountain climbing, and camping, he was a long-time member of the Adirondack Mountain Club. Ed enriched the lives of many, and he is sorely missed by his family and friends.
