PSI - Issue 75

Lucrezia Contiero et al. / Procedia Structural Integrity 75 (2025) 609–615 Author name / Structural Integrity Procedia (2025)

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To further investigate this hypothesis, the experimental data of Braun et al. (Braun et al. 2023) and Selmi et al. (Selmi et al. 2023) will be re-analysed by adopting the Peak Stress Method (PSM)(Livieri and Lazzarin 2005; Meneghetti and Campagnolo 2020; Meneghetti and Lazzarin 2007), and compared with the design scatter band calibrated on structural steels under uniaxial (mode I) loadings. Should a systematic deviation be observed, a newly calibrated PSM-based fatigue design scatter band would be necessary, as it was previously reported by Meneghetti et al. (Meneghetti et al. 2020) to deal with austempered ductile iron-to-steel dissimilar arc-welded joints. 4. Conclusions The experimental results available in the literature and referred to homogeneous and dissimilar butt-welded joints including an AMed part made of 316L stainless steel highlight a significant mismatch with the fatigue design curves provided by Eurocode 3 (Eurocode 3 2010). In particular, the standard design approach results in conservative fatigue strength estimations. However, the main discrepancy lies in the slope of the S – N curve, which differs markedly from that observed in the experimental datasets (k = 3 for Eurocode 3 versus k = 7.5 of the experimental data). The fitted S – N curve derived from the experimental dataset indicates a fatigue endurance limit of 184 MPa at 2 ∙ 10⁶ cycles, in contrast with the FAT class 80 MPa suggested by the standard (Eurocode 3 2010). This deviation suggests the need for a reassessment of the slope parameter when dealing with welded joints made of austenitic stainless steels, particularly when the components include additively manufactured (AMed) parts. The comparison with data reported by (Peng et al.) on conventionally manufactured 316L welded joints supports the hypothesis that the observed behaviour is primarily governed by the material class, i.e., austenitic stainless steel, rather than by the manufacturing process. This suggests that the discrepancies observed for AMed joints are not exclusive to additive manufacturing, but rather reflect a more general limitation of the current fatigue assessment approaches when applied to austenitic stainless steels. Accordingly, the adoption of fatigue design curves specifically calibrated for austenitic stainless steels, irrespective of the production method (AM or conventional), is recommended. The application of Peak Stress Method (PSM) to the available experimental datasets will serve to verify whether the existing scatter band calibrated for structural steels is also suitable for austenitic stainless steels. If deviations will be observed, a dedicated fatigue scatter band will be derived for this material class, ensuring a reliable and robust fatigue design framework for AM-based and traditionally manufactured components. Acknowledgements This study was carried out within the MICS (Made in Italy – Circular and Sustainable) Extended Partnership and received funding from the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.3 – D.D. 1551.11-10- 2022, PE00000004). This manuscript reflects only the authors’ views and opinions, neither the European Union nor the European Commission can be considered responsible for them. References Braun, Moritz, Jan Schubnell, Ardeshir Sarmast, Harihara Subramanian, Lutz Reissig, Felix Altenhöner, Shahram Sheikhi, Finn Renken, and Sören Ehlers. 2023. “Mechanical Behavior of Additively and Conventionally Manufactured 316L Stainless Steel Plates Joine d by Gas Metal Arc Welding.” Journal of Materials Research and Technology 24:1692 – 1705. doi:10.1016/j.jmrt.2023.03.080. Eurocode 3 : design of steel structures. 2010. BSI. Hobbacher, A. F. n.d. IIW Collection Recommendations for Fatigue Design of Welded Joints and Components . http://www.springer.com/series/13906. Lazzarin P, Sonsino C M, and Zambardi R. 2004. “Notch Stress Intensity Approach to Assess the Multiaxial Fatigue Strength of Welded Tube‐to‐flange Joints Subjected to Combined Loadings.” Fatigue Fract. Eng. Mater. Struct. 27:127 – 40. Lazzarin P, and Tovo R. 1998. A NOTCH INTENSITY FACTOR APPROACH TO THE STRESS ANALYSIS OF WELDS . Vol. 21. Lazzarin, P., and R. Tovo. 1998. A NOTCH INTENSITY FACTOR APPROACH TO THE STRESS ANALYSIS OF