Dislocation-drag contribution to high-rate plastic deformation in shock-loaded tantalum
Time-resolved plastic waves in plate-impact experiments give information on relation between applied shear stress and plastic strain rate at low plastic strain. This information is different from that obtained at intermediate strain rates using Hopkinson bar techniques, because the material deformation state is driven briefly into the regime dominated by dislocation drag. Two VISAR records of particle velocity at the tantalum/sapphire (window) interface are obtained for symmetric impact producing peak in-situ longitudinal stresses of 75 and 111 kbar. Rise-times of plastic waves are about l00 and 50 ns, respectively, with peak strain rates of about 2 {times} l0{sup 5} and 8.5 {times} l0{sup 5}/s, respectively, as determined by weak-shock analysis. These data show a much stronger dependence of plastic strain rate on applied shear stress than predicted by linear viscous drag models in combination with thermal activation through a large Peierls barrier. The data also show complex evolution of the mobile dislocation density during early stages of high-rate plastic flow. This measurement and corresponding analysis aid significantly in establishing the fundamental picture of dynamic deformation of metals and the evolution of the internal material state at early times following shock compression.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10177645
- Report Number(s):
- LA-UR-93-2799; CONF-930676-29; ON: DE93018286
- Resource Relation:
- Conference: 14. international conference of the International Association for the Advancement of High Pressure Science and Technology,Colorado Springs, CO (United States),27 Jun - 2 Jul 1993; Other Information: PBD: [1993]
- Country of Publication:
- United States
- Language:
- English
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