A Parameter Governing the Concentration of Crystal Lattice Defects in Shock-Compressed Copper

Experiments on measuring the electrical resistance of copper foil under shock compression are analyzed in order to calculate the key parameters governing the concentration of shock-induced defects in metal. The concentration of point defects in the crystal structure of copper samples placed in various sample holders (Plexiglas, Getinaks, and fluoropolymer) is estimated using the excess electrical resistance of metal. Evidently, the sample holder material affects the number of defects arising in shock-compressed metal. A sample holder with a higher shock impedance corresponds to a lower concentration of defects in the sample (at the same shock wave pressure in the sample holder). For the purpose of explaining the experimental results, a physical model of generation of crystal structure defects under shock-wave compression is formulated. According to the model, defects are formed when during material compression at the shock wave front and remain “frozen-in” upon unloading. The secondary compression of material yields a new batch of defects, leading to their accumulation. It is hypothesized that the key parameter for the number of defects arising during dynamic loading is the algebraic sum of metal deformations at each stage of shock compression. The data presented in terms of concentration of defects–deformation variables yield a relationship that compensates for differences in the sample holder material. The analysis suggests that the sum of deformations can be considered as a parameter determining the concentration of defects generated during the shock compression of copper.