DYNAMIC FAILURE - MECHANICAL AND MICROSTRUCTURAL ASPECTS

Dynamic failure can be divided into three classes: failure in tension, in compression, and in shear. The principal physical phenomena involved in dynamic failure are identified, and the mechanical models which incorporate them are reviewed. Dynamic failure of ductile metals in tension takes place by the nucleation, growth, and coalescence of voids. For brittle materials, it takes place by the nucleation, growth, and coalescence of cracks. In dynamic failure by shear, adiabatic shear bands play a key role, and their evolution in a number of materials is reviewed. Microstructural elements affect both the initiation and propagation of shear bands, which are precursors to shear and tensile failure. Compressive failure is very important in brittle materials and occurs by the activation of existing flaws in the microstructure. Compressive failure in rocks and ceramics is described. The effects of grain size, phase transformations, heat treatments, second-phase particles, porosity and existing flaws on dynamic failure are discussed.