Response of copper to shock-wave loading at temperatures up to the melting point

Abstract

The evolution of elastic-plastic shock waves as a function of the propagation distance has been studied in 99.999% purity polycrystalline copper over the 300 to 1353 K temperature range. The free surface velocity histories of shock-loaded samples 0.1 to 2.0 mm in thickness have been recorded using the velocity interferometer. The measured decay of the elastic precursor waves has been converted into relationships between the shear stress at Hugoniot elastic limit and the initial plastic strain rate. Independently of the temperature, the initial densities of mobile dislocations in a range of 2.5×106 cm−2 to 5×108 cm−2 are required to provide observed initial strain rates varied from 2.3×103 s−1 to 2×106 s−1. Above 1100 K, the shape of the elastic precursor wave changes with the appearance of a sharp spike at its front part. This change is treated in terms of nucleation and multiplication of mobile dislocations. An analysis of the rise times of the plastic shock waves has shown that for the same level of shear stress, the plastic strain rates after a 2% compressive strain increase with respect to those just behind the elastic precursor front by a factor of 300 at 300 K and by a factor of 30 at 1353 K.