Hydrodynamic Richtmyer-Meshkov Instability of Metallic Solids Used to Assess Material Deformation at High Strain-Rates

Abstract

Material strength properties for metals under shock loading conditions were investigated using high-fidelity, ultra-high-speed X-ray diagnostics. High-strain rate Richtmyer-Meshkov instability (RMI) experiments were performed with an explosive powder driven gas gun at the Advanced Photon Source (APS) located at Argonne National Laboratory. Metal targets (copper and aluminum) with a prescribed sinusoidal interface, were studied using photonic Doppler velocimetry (PDV) and X-ray phase contrast imaging (PCI). The metal targets were impacted at velocities up to ~2.25 mm/μs with subsequent maximum strain rates ranging between 107–108 s−1. The instability was recorded using X-ray PCI having a spatial resolution of 2–3 microns with sub-nanosecond exposures. Due to the constructive/destructive interference of X-rays and other challenges with artifacts associated with PCI, edge extraction must be robust against deviations in brightness, contrast, and noise. For the experimental images, a phase congruency feature detection algorithm outputs quantitative descriptors of edges for the metal jet size and shape. Computational hydrocode simulations were used to fit parameters for various strength models, with good agreement. The spatial and temporal resolution of our measurements allow validation and expansion of previously documented literature on these materials.