Enhanced spall strength of single crystal aluminum by temperature rise mitigation and structural phase transition under shock pulse

Abstract

Investigating the spalling behavior is beneficial for the microscale modeling of impact failure. However, the correlation between pulse shape and spallation remains elusive due to limited experimental methods. Here, we simulate the shock deformation and spalling behavior of [100] single-crystal aluminum by Molecular Dynamics under equivalent ramp waves, square waves, and decaying shock waves. The synergistic effects of structural transition and thermodynamic path from the pulse shape affect the systems' fracture. Despite the intersecting influences of spall mechanisms like defects dominating heterogeneous void nucleation, pulse shape primarily affects the spall strength by influencing the compression temperature rise. Higher spall strength σsp and milder injuries in a wide range are achieved by the ramp wave loading pattern through gradual compression with subtle temperature softening. Additionally, pulse shape regulates the evolution of damage through wave propagation and applied tensile strain rates, in which a ramp wave causes rapid and a decaying shock wave delays the coalescence of voids. This study provides new insight for predicting the dynamic failure of metal materials.