Welding processes are widely used in different industries. Due to the high speed and efficiency, the submerged arc welding (SAW), on welding of thick plates is widely used for manufacturing of pipes, ships, etc. This process causes stress and strain in different pieces that is necessary to know them for determining work piece life time. The main goal of this dissertation is to simulate three-dimensional model of submerge arc welding spiral pipes by using ANSYS commercial software developing related ANSYS codes (macros) in order to estimate residual stresses after the process. The simulation process is done uncouple thermal-mechanical. First thermal finite element model was analyzed and the results of the thermal solution was used to load on mechanical model and then by the finite element analysis of the mechanical model, the residual stresses was computed. The temperature distributions were predicted by using the thermal simulation such as the temperature history was calculated from the thermal model. In this analysis, the weld heat source model based on the Goldak’s double-ellipsoid power density distribution was presented. After the thermal model was analyzed and the temperature history was achieved, the mechanical model was investigated. Finally the welding residual stress distributions were calculated. It was seen from the 1st principal stress that there was a huge tensile residual stress near the welding zone. It was necessary to decrease the residual stresses in the welding process, In order to avoid the welding cracks. The huge tensile residual stresses have to be reduced. One of the industrial solutions is to apply very high internal pressure which is named hydrostatic test process. Finally residual stress distributions after welding process were compared with the residual stresses after hydrostatic test process. Due to perform hydrostatic test process, the residual stress was decreased. In this study, the experimental data was measured by using hole-drilling method. This method is a technique for measuring residual stress. The simulation results were compared with experimental data to approve the precision of the modeling. Comparison between residual stress distributions which measured by experimental and the numerical analysis, are given that the experimental data validate the exactness of the finite element method from estimating the residual stress distributions. Therefore, the proposed finite element modeling have the capability of analyzing the residual stresses of the spiral welded pipes.
