PSI - Issue 75

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

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Author name / Structural Integrity Procedia (2025)

Fig. 2. Fatigue strength of homogeneous and dissimilar full-penetration butt-weld joints according to the nominal stress approach. Comparison between experimental data of (Braun et al. 2023; Selmi et al. 2023) and the design curve provided by Eurocode 3 for structural steel; FAT class 80 MPa, inverse slope k = 3 (Eurocode 3 2010) 3. (Eurocode 3 2010; Hobbacher et al. 2024)(Lazzarin P, Sonsino C M, and Zambardi R 2004; Lazzarin P and Tovo R. 1998; Radaj D, Sonsino C M, and Fricke W 2006)(Lazzarin and Tovo

1998)(Livieri and Lazzarin 2005)(Meneghetti and Campagnolo 2020)(Livieri and Lazzarin 2005)(Meneghetti and Lazzarin 2007)(Meneghetti and Lazzarin 2007)Meneghetti and Campagnolo 2020Results and Discussion

The comparison between the two test series of 316L stainless steel butt-welded joints tested by Braun et al. (Braun et al. 2023) and Selmi et al. (Selmi et al. 2023) reveals that the experimental results systematically lie above the fatigue design curve recommended by international standards (Eurocode 3 2010; Hobbacher et al. 2024). In particular, the fatigue life predictions obtained by applying Eurocode 3 appear markedly on the safe side throughout the high-cycle fatigue regime. A notable discrepancy is observed in terms of the slope of the S – N curve. The fitted curve, characterized by an inverse slope k = 7.5, deviates substantially from the Eurocode 3 reference curve ( k = 3). This difference indicates that the standard curve does not accurately capture the slope of the experimental trend within the investigated range. Eurocode 3 provides fatigue design curves for welded joints based on joint configuration and is primarily intended for conventional manufacturing processes involving structural steels; however, it is typically extended also to stainless steels. Peng et al. (Peng, Chen, and Dong 2019) investigated the fatigue behaviour of 316L stainless steel butt-welded joints produced from hot-rolled plates and reported findings similar to those highlighted in Fig. 2. Their results also revealed notable variations in the slopes of the experimental S – N curves obtained from different data series. Although the Eurocode 3 fatigue design curve provide conservative estimates in the high-cycle regime, it does not accurately capture the slope of the experimental S – N trends, which appear steeper (e.g., k = 8.5) for the arc-welded butt joints (WR-WR) manufactured from hot rolled austenitic stainless steels, as reported by (Peng et al. 2019). This observation is consistent with the findings of the present study on both homogeneous and dissimilar LPBF 316L butt-welded joints, where differences in slope were also observed. Based on these findings, it may be inferred that the observed discrepancy is not related to the manufacturing process of the welded parts (AM vs. conventional), but rather to the intrinsic fatigue response of the welded austenitic stainless steel itself. Consequently, it is reasonable to assume that fatigue design curves calibrated on hot-rolled 316L joints may also be suitable for AMed joints, provided that the same material class is used, although a re-evaluation of the applicable slopes and endurance limits may be recommended.