PSI - Issue 79

Ibrahim T. Teke et al. / Procedia Structural Integrity 79 (2026) 17–25

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As illustrated in Fig. 3, the algorithm's simulation of thermal strain produces a biaxial stress condition. This is essential for capturing the realistic nonlinear failure mechanics — specifically in shear and axial modes — of spot welds across a range of loading conditions, from high-load to fatigue failure. In contrast, models omitting this thermal strain predict an inaccurate, homogeneous, and linear failure pattern. The ability to fit empirical data is therefore achieved by using a linear isotropic elastic material model that is first pre-stressed with these thermal strains. The thermal strain generation algorithm creates a distinct difference in the model's response: it clearly reveals shear behavior at 4.05 kN and axial behavior at 1.8 kN. This contrast highlights the algorithm's critical role. Without it, the results for both load cases are indistinguishable and fail to capture these different failure modes.

Fig. 3. Biaxility indication of Mg-Al dissimilar joint with prestress and without prestress.

4. Conclusions This study proposed a fatigue life prediction framework for spot-welded joints by combining a thermal strain-based prestress algorithm with the Morrow mean stress correction model. The key findings are: • Thermal prestress integration improves fatigue life predictions, especially for dissimilar joints with high residual stresses. • The Morrow model effectively captures mean stress effects across various joint types (TS, SLJ, MTS). • A unified simulation setup was used without geometry-specific recalibration. • Predictions showed good agreement with experimental data, mostly within a ±2× error band. • The method is computationally efficient and suitable for industrial applications in automotive and aerospace structures. References Akbulut, M. (2021). Parametric investigation into fatigue life behaviour of spot welded tensile shear test samples. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 235(19), 4119 – 4128. Akbulut, M., & Ertas, A.H. (2021). A comparative study on fatigue life prediction of spot welded coach peel (CP) and modified coach peel (MCP) type test specimens. In Proceedings of the 8th International Conference on Fracture, Fatigue and Wear (FFW2020). Lecture Notes in Mechanical Engineering. Springer, Singapore, 443 – 454.