Inelastic Deformation of Metals Under Dynamic Loading.
Final rept. 1 Jul 73-30 Jun 76,
BROWN UNIV PROVIDENCE R I DIV OF ENGINEERING
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Torsional split-Hopkinson bar experiments, involving jumps in strain rate from 0.0001s to 1000s have been carried out on four metals 1100-0 aluminum, OFHC copper, zinc, AZ30B magnesium at temperatures ranging from -200C to 250C. In addition, the effect of annealing temperature on the strain rate sensitivity of the flow stress has been examined for OFHC copper and a tellurium-doped copper alloy, Amtel. Effects of strain rate and strain rate history observed in these experiments have been examined within the framework of a theory of thermally activated motion, multiplication and annihilation of dislocations. Wavefront and Late-time asymptotic solutions have been obtained for wave propagation in linear elastic and visco-elastic bilaminates. Plastic waves of combined stress have been analyzed using a self-consistent slip model to characterize the stress-strain behavior of polycrystalline aluminum. Solutions have been obtained for three hardening models in which slip on one slip system increases the yield stress on 1 that system only, 2 all systems equally, 3 to a greater degree on nonco-planar systems. Comparison of theory with experiment shows better agreement than when smooth yield surface constitutive models are used. Author