PSI - Issue 79

A. Bacco et al. / Procedia Structural Integrity 79 (2026) 335–341

340

b

Fig. 3. Residual stress in a longitudinal path: (a) transversal residual stress; (b) longitudinal residual stress

4. Conclusion This study proposed a decoupled numerical analysis using FEM to simulate the welding process of a dissimilar steel-cast iron butt joint and to assess the thermo-mechanical responses. The simulation of the FCAW process, implemented using the “birth-and-death” method, made it possible to obtain the temperature distribution during the welding and cooling phases, as well as to analyse the induced residual stresses. The analysis showed that thermal gradients generated during the welding process induce significant residual stresses, with local values exceeding the yield strength of the material along the transverse and longitudinal paths. On one hand, along the transverse path, the longitudinal stresses are significantly higher than the transverse ones, and a discontinuity in the stress profile was observed at the transition between the steel plate and the molten zone. This discontinuity is attributed to the fact that, in the model, the filler material was assumed to have the same properties as cast iron. On the other hand, along the longitudinal path, the residual stresses distribution follows the sequence of welding passes, with high transverse and compressive stresses observed at the weld ends, in contrast to the predominantly tensile behaviour observed in the rest of the joint. Furthermore, the residual stresses in the transverse direction do not exhibit a symmetrical distribution, as typically observed in steel-steel joints. Instead, a stress peak is located in correspondence of the cast iron plate, for both the longitudinal and transverse paths. These results demonstrate that welding dissimilar steel-cast iron joints leads to a non-uniform distribution of residual stresses, strongly influenced by the thermo-mechanical properties of the involved materials. Therefore, the use of FEM for thermo-mechanical simulations proves to be an essential tool for the characterization of dissimilar joints, allowing the prediction of mechanical criticalities and the definition of process strategies aimed at reducing residual stresses and improving the durability of the welded component. Furthermore, the model developed in this study provides a solid foundation for future design and optimization tasks, contributing to the advancement of more robust and high-performance welded components. Acknowledgements This research was founded in project PRIN 2022, Prot. n. 2022EY5JAL, entitled “Design for structural strength and durability of hybrid joints between dissimilar metal materials: experimental characterisation, theoretical modeling and computationally efficient structural analyses”. Public notice n. 104/2022 of 02/02/2022. CUP D53D23003510006. The objectives of the project are aligned with Piano Nazionale di Ripresa e Resilienza (PNRR) - Mission 4: Istruzione e ricerca, Componente 2: Dalla ricerca all’impresa, Investimento 1.1: Fondo per il Programma Nazionale della Ricerca