Reloading and Unloading Response of Shocked Aluminum Single Crystals: Time-Dependent Anisotropic Material Description

To gain insight into the inelastic deformation mechanisms governing reloading and unloading of shocked Al, wave propagation simulations were performed for Al single crystals shocked to 13 GPa along [100], [110], and [111] directions. The simulations utilized a time-dependent anisotropic material model based on a dislocation dynamics description of shock- induced elastic-plastic deformation. The simulation results provide good qualitative agreement with the measured wave profile data [Huang and Asay, J. Appl. Phys. 101, 063550 (2007)], including reloading and unloading features previously identified with quasi-elastic response. Deviations from the ideal elastic-plastic response in shocked Al single crystals can be understood in terms of time-dependent material response. Therefore, a complete understanding of the reloading and unloading response of shocked polycrystalline solids may require consideration of both time-dependent response and material inhomogeneity (resulting in a distribution of shear stresses in the shocked state). Work supported by DOE/NNSA.