5 - Dynamic shear failure: The underlying physics

Abstract

High strain rate deformation often includes adiabatic heating, which increases the temperature of the deforming material. Adiabatic heating can influence the plastic deformation, fracture, microstructural evolution, and the overall physical and chemical processes that govern the dynamic deformation process. The amount of heating is a complex function of at least the structure of the material, loading mode and rate, as well as the acting microplasticity mechanisms. Localization of shear deformation, in particular, can lead to the formation of narrow and highly intense deformation bands where the adiabatic temperature increase can be significant. Dynamic shear fracture is often the result of complex interplay between plastic deformation, strain and strain rate hardening, thermal softening caused by adiabatic heating, dynamic recovery and recrystallization, as well as imperfections in the material. This chapter presents the fundamental principles of adiabatic heating and dynamic shear failure. Heat conversion during plastic deformation of metals is discussed in detail along with the current interpretations of the Taylor-Quinney coefficient. This chapter also describes selected models and theories describing dynamic shear failure with special focus and attention to how the microstructural effects are described in the current literature.