Professor, Lehigh University, Bethlehem, PA
Pages: 32 Published: Jan 1987
The macroscopic and microscopic features of fracture surfaces in metal alloys, polymeric solids, and their composites are examined with particular attention given to the appearance of fatigue damage micromorphology. Macroscopic features such as chevron markings, shear lips, and fatigue clam shell bands and ratchet lines are observed in metal and polymer alloys and are useful in identifying the crack origin, direction of crack growth, and stress state. Certain micromechanisms are common to both metals and plastics (for example, microvoid coalescence, interfacial separation, river markings, and fatigue striations), whereas other fracture markings are unique to a particular material as a result of different microstructures and deformation processes (for example, craze fracture markings and discontinuous growth bands). In general, fracture surface features are seen to depend on the magnitude of the crack driving force, scale of the microstructure relative to the crack tip plastic zone size, and the viscoelastic state of the material.
fractography, fatigue, polymers, metals, composites, microstructure, deformation mechanisms, crazing
Paper ID: STP25613S