Thermal stress analysis due to welding processes by the finite element method

A finite element model has been developed to predict the residual stresses generated in weldments during fabrication. The thermal history of the weld piece is computed using a three-dimensional heat flow model which serves as input for computation of stresses. A micro-structural model, based on the Avrami equation, and the grain growth law have also been employed to predict the grain growth due to welding. A coupled thermal elastic visco-plastic formulation including the micro-structural changes has been developed to predict the overall deformations and residual stresses caused by a welding thermal cycle. The model is applied to an austenitic type of steel, namely AISI 308, and the predictions are in good agreement with experimental results reported in the literature. The longitudinal stresses are found to be as high as the yield stress, and the transverse stresses are found to be almost half of the longitudinal stresses.