ИСТИНА

Introduction. The shock-wave techniques present a powerful tool for studying the properties of materials at extremely high strain rates with well-controllable loading conditions. Progress in investigations into high-rate deformation, fracture, and physico-chemical transformations in shock waves has been provided by the development of techniques for measuring wave profiles with a high spatial and temporal resolution. Modern methods for the recording of pressure and particle velocity histories made it possible to take into consideration the structural details of compression and rarefaction waves and their evolution, thereby making available the information about a material response to intense dynamic loads. At the present time there exists extensive experimental information on the elastic-plastic and strength properties of technical metals and alloys, geological materials, ceramics, glasses, polymers and elastomers, ductile and brittle single crystals in the microsecond and nanosecond time ranges. The time range available for shock-wave measurements has been recently expanded to picoseconds and approaching the ultimate tensile and shear strength values becomes real. The experimental data form the basis for developing constitutive equations and models of high-rate inelastic deformation and fracturing, as well as macrokinetic models of physico-chemical transformations, which are required to calculate explosions, high-speed impacts, and the interaction of high-power radiation pulses with matter. New data on high-rate deformation and fracture. In the presentation, processes and phenomena of different scale which are associated with extremely high pressures, temperatures and exceedingly high rates of their variations are discussed. We present new and, in some cases, unexpected results of investigations into the strength properties of ductile and brittle materials, phase transitions and polymorphous transformations under submicrosecond-long shock-wave loading. Approaching the ultimate (“ideal”) shear and tensile strength values has been realized in experiments with femtosecond pulse laser. Available for measurements range of strain rates has been expanded last years up to 109 s-1. Whereas response of hard alloys to the shock-wave loading at elevated temperatures does not much differ from their behavior at low and moderate strain rates, an anomalous growth of the dynamic yield stress with increasing the temperature was observed in some ductile metals. The effects of superheating of metal single crystals and pre-melting of polycrystalline metals under dynamic tension were discovered in shock-wave experiments. During the last decade, much attention has been given to the behavior of brittle materials. Presented in our review are some new data on the behavior of glasses, hard single crystals and ceramics under shock compression. Shock compression of silicate glass may be accompanied by formation of a failure wave which is a network of cracks that are nucleated on the surface and propagate into the elastically stressed body. The failure wave is a mode of catastrophic fracture in an elastically stressed media whose relevance is not limited to impact events. The high pressure and temperature attainable in the shock compression of solids may give rise to phase transitions and polymorphous transformations in them. Examples of investigations of such transformations of carbon, iron, and Ni-Ti shape memory alloy are discussed in the presentation.