Grain structure dependence of spall dynamics in shock loaded tantalum

We perform a gas gun experiment with shock loaded tantalum samples of varying grain structures to assess the suitability of a numerical model for simulating spall behavior. The observed differences in spall strength, as well spallation and re-compression history, are not captured in uncalibrated hydrodynamic simulations. An optimization is performed on the Johnson spall model to determine the best parameters that fit the observed trends. Linear stability analysis is used to motivate bounds on those parameters. Overall, optimized simulations agree well with the experimental results, reproducing pullback depth and recompression timescales across the different samples tested. The findings demonstrate the model is suitable for reproducing spall-induced free surface behavior across various microstructures, but also points to caution in using model coefficients for unvalidated microstructures. The experimental evidence also suggests that microstructure orientation may play less of a role in spall strength than grain size.