Pressure-shear stress wave analysis in plate impact experiments

Abstract

Numerical results are presented for the combined longitudinal and shear wave propagation in an elastic-viscoplastic solid as it occurs in high strain-rate plate impact experiments. Special attention is paid to the initial stage of the impact experiment and the effects of the specimen thickness, elastic impedances of flyer-anvil plates, and viscoplastic properties of materials on the time to reach a homogenous stress and deformation state within a specimen. The simple interpretation of experimental results which assumes a homogenous stress and deformation state within a specimen is found in general to be valid only at a much later time after impact. It is recommended that the measurement of the stress wave profiles should be made at the back face of the specimen rather than at its impact face, and that a pressure-shear stress wave analysis of the plate impact experiment should be performed to evaluate the inertial effects on the early part of experimental recordings. The comparison between measured stress wave profiles and the numerical simulation of the experiment provides a critical assessment of advanced viscoplastic models developed for applications under impact loading.