Pressure-Shear Plate Impact Experiments at High Pressures

Abstract

The pressure shear plate impact (PSPI) experiment, developed over 40 years ago by R. J. Clifton at Brown University enables the study of the dynamic strength of materials at high pressures and strain rates. Traditional PSPI experiments were typically conducted at velocities and corresponding pressures, limiting the experimental conditions not to exceed the Hugoniot Elastic Limit (HEL) of the anvil materials, with typical values of 3–7 GPa. In this work, PSPI experiments are extended to higher pressures, significantly beyond the HEL, approaching 50 GPa, using a powder gun facility at Caltech. The high-pressure and high-velocity impact regimes introduce several experimental challenges which must be overcome: (1) the inelastic behavior of the anvils at high pressures precludes traditional elastic analysis to extract the material’s strength; (2) the potential for slip between impact faces as a result of elevated temperatures and shear forces on the impact surfaces due to higher velocities and pressures; and (3) accurate measurement of the transverse velocity at large normal displacements, resulting from the higher impact velocities. New experimental capabilities have been developed to overcome each of these technical challenges, which include a new all fiber-optic heterodyne transverse velocity interferometer system. New analysis methods that account for the inelastic response of the flyer and anvil plates have also been developed for the accurate extraction of material strength properties from PSPI experiments. Friction and slip were examined, pushing to the limits of their knowledge under these extreme conditions. The new PSPI capabilities have been demonstrated using tungsten carbide and D2 tool steel anvils for measuring the strength of soda–lime glass and magnesium.