Based on the asymmetry of arc heat source due to the overlap structure and the thermal effect of hear enthalpy of metal droplet, a combined heat source model with an asymmetric four-ellipse heat source and a uniform volumetric heat source is established. According to the thermo-elastic-plastic finite element theory, the welding stress/strain evolution in MIG arc brazing-fusion welding of 1 mm thick 5050 Al alloy to 2 mm thick galvanized steel plate is analysed numerically based on the overlap joint, and then the distribution characteristics of residual stress in both sides of brazed interface are studied. The results show that the base metal of galvanized steel close to weld zone is under compressive stress, and the internal stress is gradually transformed into the tensile stress with the increase of distance from weld centre. Residual stress in weld zone at Al alloy side shows the tensile stress that reaches up to the yield strength of Al alloy at room temperature. At the weld toe, the residual stress decreases abruptly to zero or becomes compressive stress. A stress difference exists across the brazed interface, which displays the n-type distribution at different welding heat inputs. There is a negative correlation between the shear strength of brazed interface and residual stress difference at interface. As the welding heat input increases, the increasing of residual stress difference at brazed interface results in the decrease of joint shear strength. © 2021 Journal of Mechanical Engineering.
