On thermal softening and adiabatic shear failure of dynamically compressed metallic specimens in the Kolsky bar system

The issues of thermal softening and adiabatic shear failure, in dynamically compressed metals, are revisited through experiments in the Kolsky bar system. Various materials were compressed by single- and multi-step loadings and the results were analysed through a new approach to the issue of instability strain, which is based on the temperatures existing in the specimens just prior to the onset of instability. These temperatures are compared with the threshold temperatures, which mark the steep decrease in the strength-temperature curves. This approach accounts for most of the materials we tested. However, the brittle behaviour of the titanium and magnesium alloys, which fail at a very low strain, should be treated by a different approach.