Studies in brittle and ductile failure

Chapters I and II present a fracture mechanics framework for quantifying crack tip constraint. The application of fracture mechanics based on the J-integral is limited to conditions of high crack tip constraint. The two parameter ;Under low constraint conditions ductile failure by hole growth is a primary fracture mechanism. Chapter III examines hole growth and coalescence. It is seen that the level of stress triaxiality required for rapid hole growth is considerably greater than the maximum levels generated ahead of a crack tip. This suggests that additional mechanisms are required to explain the growth and coalescence of voids ahead of a crack.;Chapters IV and V deal with interfacial failure. Metal/ceramic interfaces are found in many advanced material systems. In these materials interfacial fracture is common and may determine the overall mechanical response. Chapter IV reviews the theory of interfacial fracture mechanics and presents specimens for determining interfacial fracture toughness. The specimens presented can be used to investigate interfacial fracture toughness over a range of mode mixities. Chapter V presents fracture data for a niobium/alumina pair obtained from the four point bend bar. Interfacial fracture toughness increases significantly as the ratio of shear to normal tractions along the interface is increased.