A two-wave shock structure-elastic precursor followed by an inelastic compression wave-is observed in single crystal and polycrystalline diamond laser shock compressed to peak stresses as high as 800 GPa. The Hugoniot elastic limits are measured to be 80 (+/-12), 81 (+/-6), and 60 (+/-3) GPa for the <100 >, <110 >, and <111 > orientations of single crystals with the directional dependence attributable to the relative increase in strength under confining stress. These values imply a single crystal yield strength approximately 1/3 of theoretical predictions. The measurements reveal clear deviations from an elastic-plastic response upon dynamic yielding with significant relaxation toward an isotropic stress state for shock stresses of at least 160 GPa. Previously reported signatures of melting at 700-800 GPa along the diamond Hugoniot may be related to the transition from a two-wave to a single-wave structure, supporting the interpretation that melting begins at lower stresses (similar to 600 GPa) with the appearance of an optically reflecting phase of carbon.
|Number of pages||19|
|Journal||Physical review B: Condensed matter and materials physics|
|Publication status||Published - Jan 2010|
- THEORETICAL STRENGTH
- DYNAMIC COMPRESSION
- WAVE COMPRESSION