Pressure-shear plate impact experiments at very high pressures

Abstract

Recent modifications of a powder gun facility at Caltech have enabled pressure shear plate impact (PSPI) experiments on materials at very high strain rates (>10⁷ s⁻¹) and pressures (>20 GPa), that have not been reached before. The high strain rate/pressure regime expands significantly the advantages of this well-studied technique. However, it requires overcoming several challenges including requiring a new approach for analysis of the experimental measurements, to extract the material’s strength. At high pressures, standard anvils such as steel and tungsten carbide (WC) do not remain elastic, and their inelastic behavior needs to be accounted for in the analysis. The methodology presented here extracts the strength of the material using a hybrid method, combining numerical simulations to simultaneously match both the normal and transverse free surface velocity measurements. First, the inelastic response of the anvils is measured using symmetric PSPI experiments and a material model is calibrated to best match the experimental measurements. Then, measuring the response including the material of interest in a sandwich PSPI configuration, the anvil's material model is used for the analysis and the extraction of the strength of the material of interest. The methodology is demonstrated for soda-lime glass with WC anvils and pure magnesium with steel anvils. The proposed methodology has the potential to expand the PSPI experiments to higher pressures and strain rates.