ИСТИНА

The shock-wave techniques provide unique capabilities to study mechanical behavior of materials at extremely high strain rates. The latest results of investigations into high-rate inelastic deformation, fracture and polymorphous transformations of solids under shock-wave loading are reviewed from the view point of real and potential capabilities of the method. Recent experimental data on the elastic precursor decay and rise times of plastic shock waves in several metals and alloys in various structural states at normal and elevated temperatures are discussed and systematized. The data on precursor decay include measurements at micron and submicron distances where realized shear stresses are comparable with their ultimate (“ideal”) values. Results of measurements have been transformed into dependences of initial plastic strain rate on the shear stress. The strong non-linearity of these dependences is treated as an evidence of nucleation of dislocations under applied stresses. 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 that is treated as an evidence of intense multiplication of dislocations. The multiplication processes may change the shape of the elastic precursor wave with appearance of a sharp spike at its front part as it was observed in vanadium after annealing and in copper at increasing test temperature. The experiments revealed also unexpected unusual oscillating regime of the elastic precursor decay in vanadium. 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 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.