Coupled thermomechanical FE analysis of multi-pass welding in thick pipe

This study investigates the mechanical principles that dictate the changes in stress and strain during the welding of pipes, and presents the findings of a thermal-structural analysis of multi-pass welding. The deep-grooved thick pipe is considered to join with MIG welding. These joints need time consuming slow multi-pass welding processes, so, before beginning welding, it is crucial to have a comprehensive plan in place. The existing ANN-based trained data is adopted in FE analysis to maximize the sectional area of the weld bead in order to minimize the number of weld passes. The 3D welding mesh model was developed using Hypermesh and further simulated using Simufact. Data on thermal history, residual stresses, and strain were gathered during the welding process at the outer and inner surfaces of the thick pipe. The results show that the inner surface of welded pipes endures much more axial and hoop compressive plastic strain than the outer surface. After welding the hoop plastic strain experiences significant growth due to thermal shrinkage, while the axial plastic strain on the inner surface increases gradually. Results also demonstrate that the axial stresses are tensile in nature on the inner surface and compressive on the outer surface. The heat-affected zone displays the highest residual stresses, posing a risk of potential weld failure in this area.