A one-dimensional two-phase approach to modeling graded density impact experiments

Here, we present a straightforward one-dimensional, two-phase methodology for modeling gas-gun-driven graded density impact (GDI) experiments. GDI experiments have the potential to probe a much larger range of thermodynamic space than single Hugoniot impact experiments. Previous modeling efforts (Aslam, McBride, Rai, Hooks, Stull and Jensen, Journal of Applied Physics, 2022) have demonstrated the potential of this approach for simulating atomically mixed GDI experiments. In that work, pressure and temperature equilibrium between the metallic phases was found to be a valid approximation, given the nanosecond timescales typical of modern diagnostics such as photon Doppler velocimetry (PDV). However, as length scales increase—such as in the bed-of-nails-type experiment (Goff, Lang, Markland, Aslam and Whitworth, AIP Conference Proceedings, vol. 2844, no. 1, 2023)—the timescales for thermal equilibrium lengthen, potentially invalidating previous assumptions. Additionally, prior work assumed that condensed-phase materials exhibited negligible strength within the studied range of impact velocities. In this study, we examine the implications of these modeling considerations and evaluate the two-phase modeling paradigm by validating it against experimental results.