Inferring the high-pressure strength of copper by measurement of longitudinal sound speed in a symmetric impact and release experiment.

Plate-impact techniques are used to investigate the equation of state and constitutive relations of copper at high pressures. The parameters are inferred from the velocity history of the surface of a shocked and then released copper plate in contact with a window. The initial shock interacts with the window interface sending a release wave back into the copper, thus, delaying any subsequent shock or release waves traveling toward the window. A backwards-characteristics code is used to regenerate the in situ particle velocities and correct for the presence of the window material. Given these corrections, the Lagrangian sound speed, pressure, and volume (density) are found, and from the sound speed, the strength parameters of the copper are calculated. This investigation finds a shear modulus of ∼100 GPa and a yield strength of ∼1 GPa for copper, at impact pressures of ∼130 GPa. The inferred shear modulus is in excellent agreement with the work of Hayes et al. The yield estimates are in broad agreement with, but are distinct from, previous theoretical and experimental studies. [ABSTRACT FROM AUTHOR]