Ductile tearing tests of 316 stainless steel wide plates containing weldments

Abstract

Twelve wide plate tests have been performed in recent years, as part of the European Fast Reactor development programme, to examine the influence of residual stresses on the fracture behaviour of Type 316 stainless steel plates and weldments. The first ten tests consisted of a study of through-thickness cracks and the last two tests addressed the behaviour of surface cracks. Results obtained from this series of tests are summarised and the ability of the R6 fracture assessment procedure to predict the results is reviewed. Significant amounts of ductile tearing under increasing applied load was shown to have occurred in both the plain plate and weldment through-thickness crack tests, prior to instability conditions being attained. R6 calculations were shown to conservatively underpredict instability applied loads for all through-thickness cracks tested. The through-thickness crack weldment tests indicated that residual stresses should be included in predicting initiation and the earliest stages of crack growth, but that they may be excluded in predicting the later stages of crack growth leading to instability. There was some evidence to suggest however that having to include residual stresses or not may depend on whether the section containing the crack is in contained yield or not. A wide plate test of a semi-elliptical crack in parent material, loaded in tension, indicated that the global limit load, although being slightly overpredictive in terms of applied load, was significantly more accurate than the local limit load approach.