Strength of Copper and Pure Iron under High Dynamic Pressures

Measurement of strength at high dynamic pressures is critical for developing material models for high-speed applications. In this study, experiments are conducted using the recently developed high-pressure shear plate impact (HPSPI) technique to investigate the strength of oxygen-free high-conductivity (OFHC) copper and pure ARMCO iron at pressures ranging from 10 to 43 GPa. In all the experiments, the strain rates are maintained on the order of 10⁵ s^-1 to extract strength as a sole function of pressure. Both copper and iron exhibit strong pressure-dependent hardening. Contrary to previous assumptions where the yield strength scales proportionally with the pressure-dependent shear modulus, experimental results for copper demonstrate that the scaling of shear strength with pressure exhibits a distinct behavior. In contrast, for iron, the scaling appears to be consistent with previous shear modulus scaling assumptions. The atomistic mechanisms responsible for pressure-dependent strength are explored using molecular dynamics simulations.