Simulation-based Study of Layered Aluminum Crystal Microstructures Subjected to Shock Loading

Abstract

A one-dimensional finite difference method allowing for anisotropic deformation is used in conjunction with a nonlinear thermoelastic-viscoplastic material model to compute the shock response of various microstructural instantiations of pure aluminum at peak stresses exceeding the Hugoniot Elastic Limit (HEL). Single crystals and layered bi-materials consisting of grains with alternating orientations relative to the direction of shock propagation -- specifically [100], [111], or low-symmetry orientations -- are impacted to peak shock stresses on the order of 5GPa. The [111] orientation [111] is observed to be stiffest both plastically and elastically, while the [100] orientation is found to be most compliant. Layered bi-materials that only demonstrate pure longitudinal waves exhibit average shock stresses, entropy production, and internal energy in between values computed for their single crystal constituents. Layered bi-materials that generate both quasi-longitudinal and quasi-transverse waves results in lower peak stresses and higher internal energy than their single crystal constituents. In bi-material systems, stress fluctuations decrease in frequency with increasing layer thickness, and peak stress amplitudes increase with layer thickness. Average dissipation depends on orientation but is relatively insensitive to layer thickness. Results of the computational method may ultimately be used to guide design of metallic systems with microstructures tailored for optimal impact resistance.