Fracture mechanical analyses concerning the load-bearing capacity of dissimilar welds in piping with circumferential cracks

In power plants numerous dissimilar welds exist between ferritic and austenitic components. The evaluation of the influence of real or postulated flaws to the load bearing and failure behaviour in the area of dissimilar welded joints, e. g. in piping of the primary circuit of nuclear power plants, is an essential part of the safety assessment of these plants. The fracture assessment of dissimilar welds containing flaws is therefore an important issue of structural integrity considerations. During the past decades several assessment procedures for the evaluation of flaws in welds have been developed mainly based on methods originally developed for homogenous materials. The main difficulties in applying these methods are that they are restricted to two different materials and the very limited experimental evaluation especially by component tests. To improve the general understanding of the influence of flaws in piping systems with dissimilar welds and to have a more reliable basis for the assessment of the fracture behaviour, full scale tests on pipes containing a weld between ferritic and austenitic steel have been performed. The test results of these tests are summarised and used for the evaluation of analytical and numerical assessment procedures. (orig.)