PSI - Issue 79

João Alves et al. / Procedia Structural Integrity 79 (2026) 326–334

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2. Methodology This research employed a two-phase methodology, namely an experimental study and a simulation study. The findings from both phases are presented in the results and discussion section, followed by the principal highlights in the conclusions. The experimental phase focused on investigating defects and fatigue behaviour. More specifically, nanotomography defect analysis was used to characterise defects. Concurrently, the simulation phase aimed to develop novel models for predicting fatigue limit and S-N curves. Regarding the proposed objectives, the developed models were established based on the experimental data, by optimising the parameters of C and m through the application of optimisation algorithms, such as Nelder-Mead and SLSQP. In the results and discussion section, the derived S-N curves are presented. Furthermore, the optimisation of parameters for defects obtained via nanotomography is discussed, and a comprehensive comparison between the predicted fatigue limit models and the experimental fatigue limit is provided. The proposed methodology is represented in Fig 1.

Fig. 1. Research Methodology

3. Experimental Procedure The specimens used in the experiments were manufactured with a titanium alloy powder, specifically Ti-6Al-4V. This powder was spherical, with diameters ranging from 20 to 53 μm . The chemical composition and the manufacturing process (SLM) is outlined in the research paper (Alves et al., 2024). The defects found were pores with a spherical shape, with a total projected area of the defect of 122.64 μ m (Alves et al., 2024). The Basquin equation was obtained experimentally (equation 13) and the obtained σ w was 55.22 MPa for 10 6 cycles (Alves et al., 2024). 0 = 3148.986 × −0.293 (13)