PSI - Issue 75

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

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1. Introduction The adoption of components produced by additive manufacturing (AM) technologies is rapidly expanding across various industrial sectors, primarily due to the potential for reduced lead times, material efficiency, design flexibility, and, notably, the capability to produce lightweight structures with complex geometries. Industries such as automotive, aerospace, and the amusement sector are increasingly focused on the integration of metallic parts produced via Laser Powder Bed Fusion (LPBF). Despite the advantages, AM technologies are constrained by limitations such as restricted build volumes and elevated production costs. To overcome these drawbacks, arc welding can be employed to join two AMed components or to combine an AMed part with a conventionally manufactured (wrought, WR) one, thus forming either homogeneous or dissimilar welded joints, respectively. Homogeneous joints represent a viable strategy for overcoming build volume limitations, whereas dissimilar joints offer a cost-effective solution by restricting AM fabrication to the customized or geometrically complex portion of the component. In particular, AMed components can be designed as structural sub-elements to be joined to existing assemblies, enabling the functional integration of diverse manufacturing processes within a single part. Once integrated into engineering structures, both homogeneous and dissimilar welded joints are exposed to cyclic service loads. Therefore, fatigue strength assessment is essential. However, current international standards and fatigue design codes (Eurocode 3 2010; Hobbacher and Baumgartner 2024) do not account for welded joints incorporating AMed parts, thus requiring a dedicated experimental characterization and potential recalibration of existing fatigue assessment criteria. In this context, the present study aims to evaluate the fatigue behavior of arc-welded butt joints made of LPBF 316L stainless steel in both homogeneous and dissimilar configurations. To this end, experimental fatigue data available in the literature (Braun et al. 2023; Selmi et al. 2023) and generated from full-penetration butt-welded joints tested under axial loading, have been compared and analyzed here. The nominal stress approach as proposed in current international standards and fatigue design codes (Eurocode 3 2010; Hobbacher et al. 2024) has been applied to the Experimental fatigue data were collected from the literature and refer to arc-welded full-penetration butt joints made of 316L austenitic stainless steel. Notably, when referring to the fatigue strength of AM-based 316L welded assemblies, the current literature makes available only experimental fatigue results generated by testing full penetration butt joints. The datasets originate from the works of Braun et al. (Braun et al. 2023) and Selmi et al. (Selmi et al. 2023). In both studies, the welded joints were produced using 316L stainless steel and incorporated parts additively manufactured (AMed) by using Laser Powder Bed Fusion (LPBF), either in homogeneous or dissimilar configurations. However, several differences can be observed between the two investigations, including variations in powder chemical composition, AM processing parameters, and the specific LPBF equipment employed. Moreover, although Gas Metal Arc Welding (GMAW) was used in both cases, different filler materials and welding parameters were adopted. A comparative summary of these aspects is provided in Table 1, which also reports the mechanical properties of the base materials used. Braun et al. (Braun et al. 2023) tested homogeneous AM-AM welded joints having thickness of 4 mm. Both parts of each joint were manufactured using the LPBF technique with the build direction oriented transversely to the longitudinal axis of the specimen, i.e. horizontally. Then, the parts have been joined by GMAW process. The authors carried out detailed dimensional analyses of the weld bead geometry and provided statistical distributions of the measured parameters. The mean values of these geometric features are summarized in Table 2. Ten specimens have been tested in the as-welded conditions under cyclic axial loading with a load ratio R = 0. Failure was defined as complete separation of the specimen. Selmi et al. (Selmi et al. 2023) investigated dissimilar full-penetration butt-welded joints consisting of one AMed 316L part and one hot-rolled 316L part (designated as AM – WR), having thickness of 4 mm. The LPBF parts were fabricated with the build direction perpendicular to the specimen axis, i.e. horizontally. Then, a GMAW process was adopted to join one AMed part to a WR part. Due to the distinct microstructures of the two base materials, namely available data. (Meneghetti and Campagnolo 2020) 2. Experimental data taken from the literature