Length Scales Associated with Dislocation Nucleation during Shock of Single-Crystalline Aluminum

Understanding the plastic response of metallic materials subjected to shock loading is critical to the development of advanced materials for aerospace and ballistics applications. The shock response of metals well over the Hugoniot elastic limit (HEL) is well documented in the literature. Less is understood about the shock response of metals slightly above the HEL where the region behind the shock front is dominated by dislocation nucleation-based plasticity. Thus, the objective of this work is to conduct non-equilibrium molecular dynamics (NEMD) simulations to provide insight into length scales for dislocation nucleation and dislocation network pattern evolution during shock of single-crystal aluminum. NEMD shock simulations with different piston velocities are conducted on single-crystal aluminum samples with select orientations that provide different dislocation slip activity. First, the elastic and plastic wave speeds are measured, which provides an understanding of the distance behind the shock wave where stable nucleation and growth of dislocation loops occurs for each crystal orientation. Second, NEMD simulation data is analyzed via spatial correlation functions to reveal length scales associated with the dislocation network evolution behind the shock front. Ultimately, this information is critical to faithfully include dislocation nucleation into mesoscale simulations of shock.