ИСТИНА

Experimental data on the resistance to inelastic deformation and fracture of several metals and alloys under shock-wave loading at normal and elevated temperatures are systematized. The data include last measurements with micron and submicron samples where realized shear and tensile stresses are comparable with their ultimate (“ideal”) values. Results of measurements of the decay of elastic precursor waves have been transformed into dependences of initial plastic strain rate on the shear stress over the strain rate range up to 109 s-1. In some cases, anomalous growth of the Hugoniot elastic limit with heating was recorded. An analysis of the rise times of plastic shock waves shows by order of magnitude faster plastic strain rates at corresponding shear stresses than that at the HEL. Results of measurements of the resistance to high-rate fracture (“spall strength”) show gradual increase of the later with increasing rate of tension and approaching the “ideal” strength in a picosecond time range. The spall strength usually decreases with heating although in less degree than the strength at low strain rates does. In general, the temperature dependences of the spall strength do not correlate with dependences of the yield stress that points on larger contribution of the fracture nucleation processes as compared to the void growth. Requirements to constitutive models for high-rate plastic deformation and fracture are formulated on the base of experimental observations. It was found the effects of work hardening and annealing on the material response at high strain rates are usually less or even may have opposite sign than that at low and moderate strain rates.