An assessment of failure probability in elastic-plastic conditions where stable tearing has occurred

Abstract

An analysis is presented for calculating the failure probability of a structure subject to general elastic-plastic loading and where the fracture mode is ductile. The main statistical variables considered are fracture toughness, flow stress and defect size. The analysis is based on a development of the R6 methodology of defect assessment. The concept of a maximum load locus is developed from the failure assessment line. The maximum load locus is used to predict those combinations of materials properties and defect size that might combine to predict structural failure after some stable crack growth. The method of determining the maximum load locus is described and some examples presented. The maximum load locus is used to estimate the failure probability on the first loading of a structure. It is also shown that the maximum load locus can be used to estimate the failure probability of a proof loaded structure where, in general, there may be a change in the dominant failure mode between proof and fault loadings. Detailed examples are presented to illustrate the analysis.