Measurement of the mechanical response of inelastic materials at high strain rates has challenged experimentalists for over fifty years. A principal difficulty in conducting and interpreting such experiments is that the dynamic loading applied to cause the high rates of deformation also introduces accelerations and consequently inertial stresses in the load measuring system and the sample. Two basic approaches have been pursued in overcoming these inertia-related difficulties. One involves simulating the stress wave propagation in the sample and using an iterative process to find a constitutive model of the material response for which simulated wave profiles agree with those monitored in the experiments. The other involves sandwiching thin samples between elastic bars or plates to determine the thickness-averaged response of the specimen from wave profiles monitored in the adjoining elastic bars or plates. This lecture will trace the development of these approaches and provide an overview of principal results that have been obtained for a wide variety of materials: metals, powders, polymers, shape-memory alloys, and biological tissues. Finally, new challenges will be addressed, e.g. miniaturization to provide direct connections with molecular dynamics simulations.

Professor Clifton received his B.S. in civil engineering from the University of Nebraska and his M.S. and Ph.D. degrees in civil engineering from Carnegie Institute of Technology, now Carnegie Mellon University. He is a fellow of the American Academy of Mechanics and the American Society of Mechanical Engineers (ASME) and a member of both the National Academy of Engineering and the American Academy of Arts and Sciences. He has spent his career at Brown University, where he was Chairman and Dean of the Division of Engineering from 1974-1979 and 1998-2003. He was also the founding Director of the NSF Materials Research Science and Engineering Center (MRSEC) at Brown. His research interests focus on the mechanical behavior of materials at high rates of deformation. He is probably best known for his development of the pressure-shear plate impact experiment and the application of this configuration to studies of plasticity, fracture, phase transformations, and friction at substantially higher rates than are accessible with more commonly used approaches. His research has been recognized by his receipt of the principal medals in his field: the Prager Medal of the Society of Engineering Science, the Murray Medal of the Society for Experimental Mechanics, and the Timoshenko Medal of the American Society of Mechanical Engineers. He has served as consultant to major firms and national laboratories, including Brookhaven National Laboratory and Sandia National Laboratories.