OVERVIEW NO 111 - CONCEPTS FOR BRIDGED CRACKS IN FRACTURE AND FATIGUE

Some recent work on length scales in bridged crack problems is reviewe d and enlarged upon. Fundamental differences are highlighted between t he solutions obtainable from bridged crack models (nonvanishing crack tip stress intensity factor; K-tip) and traditional cohesive zone mode ls (vanishing K-tip); and from models for which the bridging tractions are nonincreasing (softening) and increasing (hardening) functions of the crack opening displacement. The roles of length scales in determi ning ductility, notch sensitivity, and whether failure is catastrophic or noncatastrophic are discussed. Length scales for monotonic loading are extended to cyclic loading.