PSI - Issue 82

L. Mata et al. / Procedia Structural Integrity 82 (2026) 16–23

17

2

Mata et al. / Structural Integrity Procedia 00 (2026) 000–000

Keywords: Additive manufacturing; stress-relief heat treatment; fatigue life prediction, AlSi10Mg aluminium alloy

Nomenclature B-T

bending-torsion

d 1 d 2 F R

distance between force F and the hole centre

distance between force F and the centre of the hollow specimen

applied force

stress ratio SWT Smith-Watson-Topper T-T tension-torsion a 1

early-stage crack growth direction of crack 1 early-stage crack growth direction of crack 2

a 2 b 1 b 2 s a t a s / t

crack initiation angle of crack 1 crack initiation angle of crack 2 normal-to-shear stress ratio nominal normal stress amplitude nominal shear stress amplitude

1. Introduction In order to meet various functional requirements, mechanical components contain different geometric features that influence how the material responds to cyclic loading. Many of these features introduce material discontinuities that lead to complex stress and strain states (Zhu, 2020). In addition to their geometric configurations, mechanical components are often subjected to complex loading, such as bending-torsion or tension-torsion, among others. This involves a considerable number of variables that must be taken into account when developing numerical models to study these effects. The problem becomes even more challenging when designers work with additively manufactured materials, as the mechanical components are susceptible to internal defects, such as inclusions and porosities caused by lack of fusion, which can significantly reduce their fatigue performance (Sanaei, 2020; Branco, 2021). This behaviour can be explained by the fact that these local geometric discontinuities create stress concentration points which serve as ideal sites for fatigue crack nucleation (Campbell. 2012). Besides the internal defects, and despite the fact that laser powder bed fusion (L-PBF) produces significantly finer microstructures in aluminium alloys due to the high heating and cooling rates, this process also induces residual stresses in the material, which may play a major role in the multiaxial fatigue behaviour of these components. To mitigate this effect, considerable efforts have been made to study the influence of different heat treatments for residual stress relief. Some treatments have shown a good effect on the fatigue behaviour while others have had a detrimental effect (Fernandes, 2022; Huang, 2024). Although research on this topic has been increasing, few studies in the literature have focused on multiaxial fatigue in aluminium alloys produced by L-PBF, with most attention given to uniaxial loading scenarios. More specifically, in the case of additive manufactured AlSi10Mg alloy, there are almost no studies addressing the effect of multiaxial fatigue on the material’s behaviour (Papuga, 2024). The present work aims to fill some of these gaps and help in the understanding of these phenomena. In particular, the main objectives are the development of a numerical model capable of predicting the crack initiation locations, the early-stage crack growth directions and fatigue lives of notched hollow bars made of AlSi10Mg aluminium alloy, produced by selective laser melting, under proportional bending torsion and tension-torsion loading conditions.