Atomic insights into shock-induced spallation of single-crystal aluminum through molecular dynamics modeling

Abstract

This study investigated on the spalling behavior of single-crystal aluminum under uniaxial impact loading at the micro-scale. Under the framework of non-equilibrium molecular dynamics, the influences of impact velocity on dynamic damage evolution were comprehensively studied. The radial distribution function revealed that the material melted or partially melted when Vp was greater than 2.0 km/s; thus, the impact velocity was used as an indicator to make a distinction between releasing melting (2.0 km/s < Vp < 4.0 km/s) and compression melting (Vp > 4.0 km/s). It was found that the spallation behavior could be characterized by void nucleation, growth, and coalescence. However, the mechanism of void nucleation and growth during classical spallation was completely different from that in micro-spallation. The former was mainly accompanied by the accumulation of countable void nucleation and growth, and consequently, the duration of the spalling process was longer. On the contrary, the micro-spallation of single-crystal aluminum was dependent on a substantial amount of void nucleations; thereby, the fracture time was less. In addition, the dependence of spallation on high strain-rate history was explored. Furthermore, the free surface velocity was determined to predict the spall strength, and it was observed that strain rate and temperature had significant effects on the spall strength. Therefore, the obtained results highlight the efficiency of the proposed analytical model for characterizing the spalling response of single-crystal aluminum induced under uniaxial impact loading.