Within the EU 7th framework programme, STYLE, a number of large-scale tests have been performed. One of these tests, Mock-Up 2 (MU-2), was performed on a through wall crack located at a repair weld adjacent to a multi-pass girth weld. The aim of MU-2 was to investigate ductile crack growth under conditions with significant levels of welding residual stress.
Post-test analysis of these tests has been presented by different partners within the programme. This has led to some differences in the interpretation of the results and a degree of scatter in the resulting predictions. The post-test analyses performed at the different UK establishments indicated that the ductile initiation may have been influenced by the presence of the residual stress field. However, the different investigations do not provide consistent estimates of the magnitude of this effect, nor do they provide equivalent results when considering the load-deformation of the pipe. It was therefore agreed that it would be beneficial to understand the source of these differences in order to provide an improved prediction.
Further post-test finite element analyses of the MU-2 test have therefore been performed to consider: 1) potential variations in material properties adopted, 2) the approach to better include the predicted residual stress field, and 3) the introduction of the defect into the stress field. This range of analyses has helped clarify the differences in the analyses performed and has provided further insight to the test results.