Properties of metals at high rates of strain

Abstract

The literature concerning the behaviour of metals at strain rates from quasi-static to ultrahigh is reviewed. Deformation mechanisms that are operative include twinning and adiabatic shear banding. These are functions of material strength, composition and microstructure. Behaviour of metals at ultra-high strain rates can be determined from the examination of soft captured shaped charge jets, as well as plate and hypervelocity impacts where shock pressures can be tens of GPa. Fracture phenomena seen at high strain rates include fragmentation and spalling. For brittle materials fragmentation is a function of material fracture toughness, as well as strain rate, while for ductile metals, material fracture strength and fracture strain appear to be important. The spall strength of metals appears to be very structure sensitive with small changes in thermomechanical processing or impurity content changing spall strength markedly.