Failure behavior prediction for resistance spot-welded three-layered dissimilar joints with advanced high-strength steel

Multi-layered sheet joints featuring both material and thickness dissimilarities offer a promising solution for lightweight body structures by reducing the number of spot welds and enabling a material-specific distribution of mechanical loads. However, the inherent complexity of the stack-up, along with the resulting changes in the welding process, poses significant challenges for accurately predicting the failure behavior of such joints. Consequently, a reliable and universally applicable prediction method is still lacking. To address these challenges, this study employs a comprehensive methodology that combines experimental investigations, numerical simulations, and analytical modeling. The failure behavior of nineteen distinct joint configurations was characterized under three representative loading modes, including cross-tension, tensile-shear, and tensile-peel. Building on these results, a novel analytical method was developed to enable the reliable prediction of the failure behavior of dissimilar three-layer resistance spot-welded joints. The proposed model demonstrated high predictive accuracy, achieving a coefficient of determination of 88.8 % under shear loading, 78.6 % under tensile loading, and 72.0 % under peel loading. The corresponding RMSE values ranged from 0.36 kN to 1.94 kN across all failure modes. These results confirm the model's robustness and applicability to multi-material, multi-thickness spot-welded joints. Based on these findings, the developed method serves as an efficient and reliable tool for evaluating the quality and safety of multi-layered spot-welded joints in lightweight thin-walled structures.