Numerical analysis of GTA welding process with emphasis on post-solidification phase transformation effects on residual stresses1

The objective of this work was to analyze the residual stress state in spot welds made in an HY-100 steel disk by an autogenous gas tungsten arc (GTA) welding process. An uncoupled thermal-mechanical finite element (FE) model was developed that took into account the effects of liquid-to-solid and solid-state phase transformations. Effects of variations in mechanical properties due to solid-state phase transformations on residual stresses in the weld were studied. Extensive experimental testing was carried out to determine the mechanical properties of HY-100 steel. The residual stresses in the disk with the spot weld were measured by a neutron diffraction (ND) technique. The FE results are in good agreement with the ND measurements. The results show that the volumetric changes associated with the austenite to martensite phase transformation in HY-100 steel significantly affect residual stresses in the weld fusion zone and the heat affected zone.