Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading

Shock loading obliquity is known to significantly alter the imposed stress tensor during shock loading-in particular the ratio of the spherical (hydrostatic) and deviatoric (shear stresses) components; this affects both shock hardening and damage evolution • Quantification of the effects of shock prestraining on the post-shock mechanical behavior, structure evolution, and damage evolution must therefore quantify the influence of all aspects of shock loading: • Shockwave profile shape (square, triangle, ramp, sweeping det. wave) • Shockwave parameters (peak stress, pulse duration, rarefaction rate) • Shockwave obliquity • Material properties (chemistry, texture, microstructure, etc.) • Twin formation during shock loading in Ta is seen to be a strong function of shockwave obliquity consistent with the effect of obliquity on the stress tensor. • Electron Backscatter Diffraction (EBSD) data can only provide valuable information on twin volume fractions. Coupling with 3-D reconstruction will facilitate quantitative volume fractions. • The concept of a "critical twinning pressure" is shown to be relevant to only pure 1-D shock loading and provides minimal insight to modeling shock effects in materials.