Welding residual stresses in a strip of a pipe

Residual stress was measured through the thickness of a strip sample of a girth welded pipe. The motivation behind this measurement was to investigate whether the segment test, commonly used in validation of Engineering Critical Assessment results, is representative of full girth welds in terms of the welding residual stress. A major rationale was to try to understand how much residual stress will be relieved due to the removal of the strip sample from the pipe. The reported results in this paper are based on aJoint Industry Project (JIP) led by DNV GL on the treatment of residual stress on pipes undergoing high plastic deformation. The paper presents measured residual stresses data in the hoop and axial direction of the pipe. In the current study, the measured residual stresses in the segment sample are found to be similar to those at similar full girth welds but showed more compressive stresses in the weld cap, more tensile stresses in the weld root, and a similar profile through the thickness. This re-distribution of residual stress can be attributed to the release of the “far field” bending stresses when the pipe was sectioned into the strip in both the hoop and axial directions.