Crack-Growth Resistance Characteristics of High-Strength Sheet Alloys

摘要

Crack propagation in a metal sheet is impeded by the inherent resistance to fracture of the alloy. This resistance is manifested by the requirement that crack growth will occur only under a rising load up to an instability load at which unstable fracture commences. If the fracture resistance curve which designates the load-crack extension relationship to instability has a unique shape for each material and is independent of most specimen dimensions, it can be a valuable tool in failure-safe design. The fracture resistance curves (R-curves) have been obtained for six high-strength sheet alloys which fractured under elastic loads. The influence of three specimen geometric variables and yield strength on the shape of the R-curve and the critical stress-intensity factor K sub c was investigated. On several alloys a comparison was made between the R-curve and K sub c value generated with a center-cracked tension (CCT) specimen and data derived from a crack-line loaded (CLL) specimen used at Armco Steel Corporation. (Author)