Residual stresses in austenitic thin-walled pipe girth welds: Manufacture and measurements

Determining residual stresses in thin-walled pipes is challenging. They are potentially difficult targets for simulation, because they may not behave as simple axisymmetric structures during welding. Thin-walled pipes are more sensitive to changes in the welding heat input than thick-walled pipes. They are also under-represented in the existing population of residual stress measurements used to generate upper bound residual stress profiles for structural integrity assessments. In this paper, residual stress characterisation of two thin-walled austenitic girth welded pipes is presented. The overall geometries of the two mock-up designs were the same; they differed in the linear heat input per pass and the total number of weld passes. The residual stress characterisation was carried out using two independent measurement techniques; the contour method and neutron diffraction. The multiple-cut contour strategy was implemented to measure the cross-sectional maps of hoop and axial stresses on axial-radial and hoop-radial planes respectively. The contour method results are compared with stresses measured using neutron diffraction and specific residual stress distribution signatures observed are discussed.