Welding stress predictions have been used in the failure assessment of multi-pass girth welds of a ferritic ASTM SA 516 steel pipe. Applying the predicted welding stresses in the failure analysis leads to less conservative results than basing the assessment on the current industrial practice of assuming residual stresses equal to the yield stress.

• A 3D WeldsimS simulation (Figure 1) is carried out using adaptive re-meshing to enable a graded mesh with sufficient spatial resolution in the fusion zone and the HAZ.
• Stresses and mechanical properties are then exported to ABAQUS by which an axis-symmetrical 2D analysis on the cross-sectional plane (Figure 2) is carried out. A significantly denser mesh is used than in the residual stress analysis.
• A crack is introduced in the critical area to initiate the failure assessment analysis.

Results (Figure3):

• Using residual stresses predicted by WeldsimS in failure analyses (Case 2), leads to a significantly  lower driving force for the failure (CTOD), than when the driving force is established from standard procedures such as the BS 7910 Level 3B (case 3).
• Integrity assessment based on residual stresses from WeldsimS will give more accurate integrity assessment of welded structures since overly conservative assumptions regarding the residual stresses can be avoided.