Fracture mechanics is a multidisciplinary engineering topic that has foundations in both mechanics and materials science. This article summarizes the microstructural aspect of fracture resistance in structural materials. It provides a discussion on basic fracture principles and schematically illustrates the mechanism of crack propagation. The article describes the fracture resistance of high-strength steels, aluminum alloys, titanium alloys, and composites such as brittle matrix-ductile phase composites and metal-matrix composites. It also lists the effects of microstructural variables on fracture toughness of steels, aluminum alloys, and titanium alloys.
This article summarizes the aspects of crack shape and irregularity that are relevant to fatigue and fracture of surface cracks. It discusses the nature of three-dimensional surface cracks and variables that influence crack shape. These variables include the grain size, residual stresses, texture, loading mode, environment, and crack coalescence. Measurement of crack shapes or aspect ratios during fatigue crack growth can be performed by a number of techniques. The article describes the estimation of the stress-intensity factor for arbitrarily-shaped cracks and failure prediction methods for arbitrarily-shaped flaws.