Effects of anelasticity in high pressure shock-release experiments

Many in the shock physics community are interested in understanding material strength during extreme loading. This has led to the development of compression-release experiments where the release portion is sensitive to material strength. During the loading reversal, the dislocations associated with plastic flow change their direction and this provokes behaviors related to anelasticity. Additionally, anelasticity produces features that are distinct from those that would arise from studying material strength under fully-developed monotonic flow. These confounding anelastic effects lead to challenges in the interpretation of strength effects in gas-gun release wave measurements. Work here focuses on modeling high-pressure gas-gun experiments (about 100 to 300 GPa) where initial release wave features help distinguish material strength and potential anelastic effects. We employ a dislocation-density-based plasticity formulation coupled with a model of anelasticity. The goal is to simultaneously calibrate selected model parameters, including those related to the anelastic response. Our approach involves training computationally-efficient (i.e., fast-running) surrogate models to faithfully reproduce hydrocode outputs, which explicitly model the flyer/target impact. Additionally, the surrogate models are paired with Bayesian model calibration to estimate parameters, assess parameters correlations, and quantify their uncertainty using a Bayesian framework.