Numerical Investigation on the Effect of Weld Spot Location on the Mechanical Performance and Adhesive–Weld Interaction in Hybrid Adhesive-Bonded/Friction-Stir-Spot-Welded AA6082/AZ31 Joints

Hybrid joining methods combining adhesive bonding (AB) and friction stir spot welding (FSSW) have attracted increasing attention for lightweight multi-material structures due to their potential to combine the advantages of both techniques. In this study, a numerical investigation of hybrid AB + FSSW joints for dissimilar AA6082 aluminum and AZ31 magnesium alloys was conducted using finite-element analysis. Three joint types were considered: adhesively bonded (AB), friction-stir-spot-welded (FSSW), and hybrid AB + FSSW joints. The influence of weld location and adhesive type on joint performance, failure behavior, and stress distribution was evaluated. Cohesive zone modeling was employed to simulate adhesive failure, while the modified Mohr–Coulomb ductile fracture criterion was used to predict fracture in the metallic substrates and weld regions. Two structural adhesives with distinct mechanical characteristics, Araldite AV138 and Nagase XNR6852 E-3, were considered. The results showed that the hybrid configuration with the weld located at the center of the overlap and the Nagase adhesive provided the most favorable performance, reaching a maximum load of approximately 9.4 kN, comparable to that of the adhesively bonded joint. In contrast, FSSW-only joints exhibited lower load-bearing capacity and predominantly failed through the weld interface. Stress analysis suggested that the adhesive layer significantly reduced stress concentrations around the weld spot, particularly when adhesive was present on both sides of the weld. The findings demonstrate that appropriate weld positioning and adhesive selection are critical parameters for maximizing the efficiency of hybrid AB + FSSW joints and indicate the feasibility of this joining strategy, based on the numerical models developed, pending experimental confirmation for dissimilar aluminum–magnesium structures.