A dislocation-based dynamic strength model for tantalum across a large range of strain rates

Abstract

We present a dislocation-based strength model for tantalum that captures the plastic deformation at high strain rates above 103s−1. The model has its origins in molecular dynamic simulations and it is implemented in a 3D continuum framework. We calibrate and validate the model using Split Hopkinson Pressure Bar, plate impact, and Richtmyer–Meshkov instability experiments. With the validated model, we can computationally generate stress–strain curves at strain rates of 103−107s−1 for samples with various initial dislocation densities. Based on the results, we show that the dynamic yield strength of annealed tantalum at high strain rates is followed by softening since mobile dislocation densities rapidly increase due to the high shear stress. This strain-softening is evident only at the high strain rate regime and it is much less pronounced in cold-worked Ta.