Examination of Metal Strength at High Strain Rates Using Richtmyer-Meshkov Instability Experiments at the Advanced Photon Source

Recent advances in ultra-high-speed x-ray diagnostics allow high-fidelity, in-situ investigation of material properties under extreme conditions. Richtmyer-Meshkov instability (RMI) experiments were performed with a gas gun in the Advanced Photon Source (APS) located at Argonne National Laboratory. Shock compressed metal targets (copper and aluminum) with a prescribed sinusoidal interface, were studied using photonic Doppler velocimetry and x-ray phase contrast imaging (PCI). These initial perturbations on the shocked metal interface evolve into jets and bubbles. The instability was recorded using x-ray PCI having a spatial resolution of 2-3 microns with sub-nanosecond exposures. Due to challenges with artifacts associated with PCI, a phase congruency feature detection was used to output quantitative descriptors of edges for the metal jet size and shape. This data is reduced systematically and reliably identifies points with impedance gradients. The jet shape and velocity provide details necessary for high-strain rate dependent strength models for shock compressed metals. While other experiments and models have been shown in literature, the added spatial and temporal resolution of our measurements allow validation and expansion of these works.