FUNDAMENTALS OF FRACTURE AND FATIGUE: A BASIS FOR ALLOY DESIGN.

Micro-mechanics and mechanisms describing fundamental aspects of failure by fatigue and fracture are examined from the perspective of alloy design of superior engineering metals and alloys. First, the physical basis for intrinsic fracture toughness in materials is derived through several micro-mechanical models for both brittle and ductile fracture, specifically for cleavage, microvoid coalescence and transitional fracture modes. Second, factors governing the rate of growth of fatigue cracks are described, with emphasis on the role of crack tip shielding mechanisms such as crack closure. Examples of the design of microstructures giving optimum resistance to fatigue crack propagation are presented, with emphasis on high temperature behavior.