The effect of vacancies on dynamic response of single crystal Cu to shock waves

Abstract

Using molecular dynamics (MD) simulations, we investigate the effect of vacancies on the dynamic response of single crystal Cu to [100] shock loading, including plasticity and spallation, for an initial vacancy concentration (cv) ranging from 0% to 2%. A fixed impact velocity is adopted, for which plasticity and spall do not occur in the defect-free Cu during compression or tension. We show that shear flow strength (compressional or tensile) and spall strength decrease with increasing cv. At the MD scales, the vacancy effect becomes pronounced for cv>0.25%, where heterogeneous nucleation of plasticity prevails. Tensile plasticity may play a key role in inducing local heating and the power-law reduction in spall strength. Void nucleation occurs preferentially at highly sheared (plastically deformed) sites.