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Walter Herrmann came to Sandia National Laboratories via the MIT Division of Sponsored Research, where he was developing his WAVE 1 finite-difference computer program for numerically calculating high-amplitude, nonlinear wave propagation in one-dimensional structures. Sandians C. Donald Lundergan and Charles F. Bild, then the director of materials and process development, along with others, recognized that computers were becoming powerful enough to realistically simulate shock-wave deformation of structures. Such deformation results from the detonation of explosives or high-velocity impact. Indeed, they were proven right; Herrmann was successful in building this capability at Sandia. During the Cold War between the United States and former Soviet Union, such capability was urgently needed for the development of new nuclear weapons.

Herrmann joined Sandia in early 1964 as supervisor of the Deformation of Structures Division. Initially, he had no staff, but he had management support to build a computer-code development team. WAVE 1 became the basis for the Sandia WONDY finite-difference computer program, which was soon used in nuclear weapons component development. Next, the Sandia TOODY computer program was developed, which enabled two-dimensional simulation and analyses of structures. Some of the important code developers included Herrmann (a formidable mathematician and computer scientist), Larry D. Bertholf, Darrell L. Hicks, R. Jeffry Lawrence, Samuel L. Thompson, Billy J. Thorne, and Robert J. Walsh. Thompson went on to develop a powerful three-dimensional code that included radiation transport.

These computer programs all required knowledge of nonlinear constitutive behavior of materials at the extreme stresses and strain rates induced by shock-wave loading. Building on Lundergan’s program of projectile plate impacts, along with data from other Sandia organizations and other laboratories, the experimental data for developing constitutive models of many types of materials—metals, ceramics, polymers, composites, foams, for example—were obtained. Names of some of the key staff members engaged in this

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