Material heterogeneity as the origin for quasi-elastic ramping and unloading

Plate impact experiments are widely used to study materials under high strain rates and pressures. However, discrepancies often arise when attempting to simulate the free surface velocity at the back of the target, even with modern and advanced material models. This work focuses on two key experimental features: the smooth rise in the elastic precursor wave and the smooth decay of the elastic release wave. We show, through mesoscopic simulations, that these features can be accurately reproduced when material strength heterogeneity is considered. To validate our model, we simulate polycrystalline metals—tantalum and copper—as well as a heterogeneous metallic composite, tungsten heavy alloy. Our results demonstrate that by incorporating mesoscopic strength variations, either due to grain orientation or a composite phase, the smoothed velocity profiles observed experimentally can be simulated while maintaining consistency with uniaxial stress compression tests.