PSI - Issue 77

L.P. Borrego et al. / Procedia Structural Integrity 77 (2026) 681–687

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(L-PBF) has emerged as a highly versatile method for producing high-performance metallic parts and revolutionized the production of complex metallic parts (Yadroitsev et al. 2021). The integration of Laser Powder Bed Fusion (LPBF) with topology optimization enables a reduction in the component weight, often by approximately 30-50% (Liu et al. 2021). In the as-built condition, AlSi10Mg microstructure presents large Al grains present a fine cellular-dendritic solidification structure with submicron-sized primary Al cells and an intercellular Si network (Krochmal et al. 2021). Research has demonstrated that AlSi10Mg parts produced by L-PBF can exhibit variations in the mechanical behavior based on the process parameters and post-treatments, like heat treatment, can improve fracture resistance and durability of these components (Jiang et al. 2023). Real-world component failures in AlSi10Mg produced by L-PBF are often related to the presence of residual stresses, which are introduced during the process. Optimizing the laser parameters and applying appropriate post processing strategies can mitigate these issues (Egger et al. 2021). Residual stresses interact with applied stresses by modifying the loading cycle, thereby modifying the effective stress ratio which can be detrimental to the fatigue life. The main objective of this work is to prove, using a real functional part, the benefits of a heat treatment previously studied by the authors (Fernandes et al. 2024a). on the fatigue behavior. The chosen functional part was a bicycle crankset, typically, made in aluminum alloy and subjected to different types of cyclic combined stress as tensile, torsional and bending (Ismail et al. (2021). 2. Finite element analysis and experimental procedure Initially, a simplest crank arm supplied by a Portuguese bike manufacturer, Miranda® (Portugal), produced through a forging process for the aluminum alloy 6061-T6, was chosen as the basis for developing a new optimized model, featuring reduced weight and a more complex geometry, to be produced by L-PBF. Second, the improved crankset design was developed from the conventional crank mentioned before. The topology optimization was performed using software such as Autodesk Inventor 2025 ® and Autodesk Inventor Nastran 2025®. By simulating loads, constraints, and materials, it generates an ideal shape for a part based on its functional requirements. It uses topology optimization to suggest lightweight designs that maintain structural integrity. The Shape Generator then analyses the part, suggesting material removal from areas that do not significantly contribute to its strength, thus creating a design that balances performance and weight. In the Shape Generator settings, the Young's modulus was 72 GPa, and the applied load was 1300 N at an angle of 45°, 65 mm from the crank arm ’s cross -sectional plane (yellow arrow in Fig. 1a), as specified in the NP EN ISO 4210 8:2019 (2019) standard for leisure bicycles. Fig. 1b shows the result of the Shape Generator analysis, achieving a weight reduction of 51% in comparison with the standard model. In this analysis, the authors considered the mechanical properties obtained in previous work (Fernandes et al. 2024b) and presented in Table 1.

Table 1. Mechanical properties of the tested aluminum alloy (Fernandes et al. 2024b). Series σ UT (MPa) σ YS (MPa)  f (%) E (GPa) As-build (AB) 435 250 4.1 72 Heat-treated (HT) 380 210 5.6 72

Thus, a new crank arm was designed through FEA in Autodesk Inventor Nastran. The FEA model was developed using a linear static analysis with 308,648 tetrahedral elements, resulting in a final shape (Fig. 2), that achieved a 26% weight reduction compared to the standard form. Observing the FEA results (Fig. 2a), it can be concluded that the maximum Von Mises stress value was 203.51 MPa, which is clearly below the yield stress listed in Table 1. After defining the final geometry, a Renishaw machine AM400 was employed to produce six crankset by the L PBF process. The additive manufacturing process was conducted under controlled conditions: the building platform was preheated to 150ºC, while the laser operated at a power of 350W, with a hatch distance of 80 µm, a scanning speed of 1.8m/s, a layer thickness of 30 µm and a rotation incremental angle of 67°. All specimens were produced in