Electrical Resistance of Copper under Multiple Shock Compression and Generation of Crystal Structure Defects

The electrical resistance of copper foil under multiple shock compression to a pressure of 40 GPa is studied experimentally in several explosive systems: in a reflected shock wave, under compression in a rigid shell, and in a layered system generating a sequence of waves of increasing amplitude. An improved design of the measuring cell is proposed, which significantly reduces the influence of parasitic eddy currents on the recorded voltage. Under shock compression, the electrical resistance of copper increases monotonically, but the growth rate depends on the loading history. Under compression by a sequence of shock waves, the electrical resistance of the metal is lower than under compression by a single shock wave (at the same incident shock pressure in the dielectric shell). In this case, the main change in the electrical resistance of copper occurs in the first shock wave. In subsequent waves, the electrical resistance also increases, but the final value is lower than in a single shock wave. The crystal structure defect concentration in a copper sample under complex loading is estimated. Under multiple compression, the defect concentration is lower than in the case of single compression (at the same wave pressure or deformation). This implies that during complex shock loading, defects are mostly generated in the early stages of compression, and subsequently there is only a relatively small increase in the number of defects. Qualitatively, the defect concentration during complex shock loading is determined by the deformation in the first shock wave.