Spallation of single crystal nickel by void nucleation at shock induced grain junctions
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Molecular dynamics (MD) simulations of spallation in single crystal nickel were performed for a range of system sizes and impact velocities. The initial compressive wave leaves a rich microstructure in its wake. The subsequent tensile waves create multiple grains and grain junctions between regions of differing crystal orientation. These grain junctions serve as void nucleation sites when the reflected tensile waves interact, leading to ductile failure. In this way, the mechanism for failure in an initially single-crystalline sample is similar to that seen experimentally in high-purity, poly-crystalline metals, in which grain boundaries are sites for void nucleation.
KeywordsImpact Velocity Void Nucleation Spall Strength Free Surface Velocity Flyer Plate
This work was funded by the ASC program at the Los Alamos National Laboratory. Sandia is a multi program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DEAC04-94AL85000. Many of the calculations were performed on the LANL QSC parallel computer using a modified version of Warp, a molecular dynamics code originally developed by Steve Plimpton at Sandia.
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