Numerical Simulation and Experimental Investigation of Residual Stresses in the Circumferential Butt GTAW of Incoloy 800H Pipes

The residual stresses developed during the circumferential butt gas tungsten arc welding (GTAW) process of Incoloy 800H pipes were simulated using the finite element method. A decoupled thermostructural model was developed in three dimensions. The element birth and death technique was used for the addition of filler material in the weld pool. The Goldak double ellipsoidal model was used to simulate the distribution of arc heat during welding. The plastic behavior of the material was described by Von Mises yield function and the bilinear kinematics hardening was assumed. To validate the thermostructural model, both temperature and residual stress distributions within the pipes were measured using thermocouples and strain gages, respectively. Good agreements were found between the experimental and simulation results. The model was then used to predict distribution of residual stresses during the GTAW of Incoloy 800H pipes and to study effects of process parameters on the residual stresses.