Developing methods to examine material constitutive response under dynamic compression and large plastic strain excursions

For understanding material performance under dynamic loading, there is significant interest in the strain-rate dependence of material response and in the degree to which high-rate response depends on initial material state. Experimental tests at high strain-rate (>10³/s) often use measurement of shape change to infer flow strength behavior and inferences are facilitated by comparisons with advanced simulations. Complementary mature techniques exist, such as the Taylor anvil, Richtmyer-Meshkov instability, and thick-walled cylinder tests, for addressing the gaps to fill in strain and strain-rate conditions accessed during high-rate loading scenarios. This talk will focus on a recently developed plate impact-based experimental test and place it in context with those other techniques. It consists of in-situ X-ray imaging to observe the closure of a cylindrical hole during the passage of a pressure pulse of controlled amplitude and duration as measured through time using multi-frame imaging. Experimental observations are compared with predictions from direct numerical simulations using flow strength models with a variety of complexity such as the Elastic-Perfectly-Plastic (EPP), Mechanical Threshold Stress (MTS), Preston-Tonks-Wallace (PTW), and Livermore Multiscale (LMS) models. The quantitative utility is in providing information about model parameters associated with high-rate hardening behavior. Additionally in such tests, severe deformation of materials can lead to inhomogeneous intense zones of localized strain, and we show this test can provide information on the onset of such competing physics.