Pressure-shear impact and the dynamic viscoplastic response of metals

Modeling dynamic plasticity and spall fracture in high density polycrystalline alloys

“…1, and sgn(x) = x/jxj, with sgn(0) = 1. Thermal softening attributed to increased dislocation mobility at high temperatures is incorporated via the power-law form (Klopp et al, 1985) g ðaÞ ¼ g…”

Rise time in shock consolidation of materials

“…Existing experimental evidence indicates that the flow strength remains relatively high and strongly rate dependent under these conditions. 10,11,15,16 Figure 2 summarizes the variation of flow stress with shear strain rate for copper over a wide range of strain rates. The prediction of Eq.…”

“…Table I lists the viscoplastic parameters defined above and the melting point m for selected materials. 10,11 Heat conduction during compaction has been neglected in our analyses. This approximation is valid for large powder particles on the order of tens of microns, where the thermal diffusion distance, is small compared with the characteristic length of the microstructure which is the average pore size.…”

“…Experimental evidence indicates that flow strength of most metals is strongly rate dependent at these strain rates. 10,11 Tong and Ravichandran 12 have recently reexamined the dynamic pore collapse problem by considering the finite elastic/viscoplastic deformation of a spherical shell. Their results indicated that strain rate, strain hardening, thermal softening, dynamic loading rate, pore size, and initial relative density play a significant role in pore collapse.…”

“…Their results indicated that strain rate, strain hardening, thermal softening, dynamic loading rate, pore size, and initial relative density play a significant role in pore collapse. In particular, a viscoplastic material model including strain-rate sensitivity, strain hardening, and thermal softening is assumed to be of the form [10][11][12] …”