Statistical distribution of times to crack initiation in service using C-130 inspection data

Abstract

Methods by which in-service crack inspection data may be reduced to yield meaningful time to crack initiation and initial flaw size data are examined. A method is developed by which inspection data consisting of time of inspection and crack length can be used to determine. crack growth constants. By using fracture mechanics the inspection data of any crack size can be normalized to an arbitrary crack size considered to be the size at which the crack initiates. Thus, the times to crack initiation and initial flaw sizes were derived.

Several statistical distributions were fitted to the times to crack initiation and to initial flaw sizes in order to describe analytically their expected behavior at each location.