Characterization of recompressed spall in copper gas gun targets

Complementary experiments and simulations are conducted to characterize the microstructure and mechanisms involved in recompression of spalled ductile metals. Soft capture experiments performed on copper targets in a gas gun include a dense secondary plate spaced behind the customary flyer to recompress the voids in the wake of the spall induced by the flyer. Control experiments are run without the secondary plate to obtain spall damage without recompression. The simulations feature explicit representation of void nucleating particles in a narrow strip of material spanning the flyer package and target. Analysis of the spall closure in the simulations reveals the void collapse mechanisms and the origin of features observed experimentally. The experiments and simulations show little trace of the prior voids, and a thin ribbon of highly strained material is the only readily observable remnant of the spall surface. (C) 2007 American Institute of Physics.