PSI - Issue 79

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

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2.2. Prestress Algorithm for Thermal Residual Effects A key innovation in this study is the incorporation of a prestress algorithm that simulates residual thermal strains generated during the resistance spot welding process. The algorithm is based on the temperature field – driven nodal displacement method described by (Teke et al., 2025a), adapted here into the ANSYS environment via a sequential loading strategy. First, a thermal loading step is applied to simulate cooling-induced shrinkage due to the mismatch in thermal expansion coefficients between dissimilar metals. The resulting displacement field is stored and introduced into the structural solver as an initial strain field before mechanical fatigue loading. This method captures the spatially varying stress gradient that arises from differential contraction, especially in dissimilar welds, and significantly improves the prediction of fatigue crack initiation zones. 2.3. Geometry, Loading, and Boundary Conditions Three commonly used specimen types were simulated to assess the model’s generalizability: • Tensile-Shear (TS) Specimen: Standard overlapping geometry, simulating shear-dominant cyclic loading (Figure 1a). • Modified Tensile-Shear (MTS) Specimen: Designed to capture out-of-plane bending effects and nugget rotation (Figure 1b). • Single-Lap Joint Tensile Specimen: Captures both axial and moment-induced strain modes (Figure 1c and 1d).

Fig. 1. Numerical validation specimens, (a) TS (Teke and Ertas, 2025), (b) MTS (Ertas and Akbulut, 2021) , (c) Single-lap (Sun et al., 2016), (d) Single-lap (Asati et al., 2022).

In all cases, the weld nugget was modeled explicitly as a circular region with heat-affected zones (HAZs) meshed separately. Contact interactions were defined between the sheets using frictional constraints. Boundary conditions replicated standard fatigue test setups, with cyclic loading applied through tab ends while fixing the opposite end to prevent rigid body motion. 2.4. Model Calibration and Validation To ensure the robustness and generalizability of the proposed fatigue prediction framework, the simulation model was validated against a broad set of experimental studies covering similar and dissimilar spot-welded joints under various configurations: • Single-Lap Joints (SLJ):