Shockless compression and release behavior of beryllium to 110 GPa

Abstract

A magnetohydrodynamic loading technique was used to shocklessly compress beryllium to peak longitudinal stresses of 19-110 GPa and, subsequently, unload in order to determine both the compressive response and also the shear stress supported upon release. Loading strain rates were on the order of 10 6s-1, while the unloading rates were nearly constant at 3 × 105s-1. Velocimetry was used to monitor the ramp and release behavior of a beryllium/lithium fluoride window interface. After applying window corrections to infer in situ beryllium velocities, a Lagrangian analysis was employed to determine the material response. The Lagrangian wavespeed-particle velocity response is integrated to generate the stress-strain path, average change in shear stress over the elastic unloading, and estimates of the shear modulus at peak compression. These data are used to infer the pressure dependence of the flow strength at the unloading rate. Comparisons to several strength models reveal good agreement to 45 GPa, but the data indicate 20%-30% higher strength near 100 GPa. © 2014 AIP Publishing LLC.