A unified approach for extracting strength information from nonsimple compression waves. Part I: Thermodynamics and numerical implementation

We describe a comprehensive method of extracting estimates of the complete plastic deformation behavior, including full deviatoric-stress/plastic-strain (τ − ψ) curves, from one-dimensional dynamic compression experiments at moderate pressures (up to ∼50 GPa). The method combines and extends selected aspects of previous approaches and features a second-order velocity interpolation function designed to accommodate highly rate-dependent phenomena. Assumptions, and the expected limitations thereof, are made explicit and kept to a minimum. In particular, we do not assume any particular plasticity model, nor do we assume that the wave propagation is either simple or steady. Instead, we allow the data themselves to constrain any such behavior. We develop generalizations of standard equation-of-state analyses that account for the effects of rate-dependent relaxation on wave speeds and paths through thermodynamic space and show the potential to extract a great deal of strength information from the details of wave propagation.