Abstract. The response of metals to shock loading is affected by a number of factors, including the unit cell and properties that affect the motion and generation of dislocations such as stacking fault energy and the Peierls stress. In an effort to increase the understanding in this area, we have chosen to investigate the response of two near ideal materials; copper as an fcc and tantalum as a bcc. We have also investigated each material in both an annealed and cold worked to 50% reduction in thickness in an attempt to understand how differences in dislocation density affect response. Measurements have been made using standard diagnostics, including stress gauges and Photonic Doppler Velocimetry as well as analysis of the shocked microstructural and mechanical response through one-dimensional recovery.
The microstructural and mechanical response of materials to shock loading is of the utmost importance in the development of constitutive models for high strain-rate applications. However, unlike a purely mechanical response, to ensure that the microstructure has been generated under conditions of pure one dimensional strain, the target assembly requires both a complex array of momentum traps to prevent lateral releases entering the specimen location from the edges and spall plates to prevent tensile interactions (spall) affecting the microstructure. In this paper, we examine these effects by performing microhardness profiles of shock loaded copper and tantalum samples. In general, variations in hardness both parallel and perpendicular to the shock direction were small indicating successful momentum trapping. Variations in hardness at different locations relative to the impact face are discussed in terms of the initial degree of cold work and the ability to generate and move dislocations in the samples.
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