RELATING CLOSURE DEVELOPMENT IN LONG CRACKS TO THE SHORT-CRACK REGIME

Crack closure mechanisms require some finite amount of crack growth to become fully operative, and this appears to be a major reason for the existence of short-crack behaviour. Although such behaviour is not always explicable in terms of an effective, closure-free, stress intensity range, there is some evidence to indicate that short-crack effects end once a closure value representative of long cracks is obtained. If the closure development distance is an 'intrinsic' property of a material, under given conditions, it should be feasible to link the extent of the short-crack regime to the closure development distance of long cracks. This paper examines such a possibility for the aluminium alloy 7017 and relates the experimental results to a simple analytical closure model developed by Jira et al.