Spallation of single crystal nickel by void nucleation at shock induced grain junctions

Molecular dynamics (MD) simulations of spallation in single crystal nickel were performed for a range of system sizes and impact velocities. The initial compressive wave leaves a rich microstructure in its wake. The subsequent tensile waves create multiple grains and grain junctions between regions of differing crystal orientation. These grain junctions serve as void nucleation sites when the reflected tensile waves interact, leading to ductile failure. In this way, the mechanism for failure in an initially single-crystalline sample is similar to that seen experimentally in highpurity, poly-crystalline metals, in which grain boundaries are sites for void nucleation.