PSI - Issue 76

Daniele Rigon et al. / Procedia Structural Integrity 76 (2026) 35–42

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Therefore, if the fatigue limit for a load ratio R = − 1 is estimated using the highest value S mea v , max , i reported in 3 coupled with the ALM model, then the e ff ective crack size due to surface roughness detected by OP alone is equal 22.4 µ m, yielding a fatigue threshold estimate ∆ σ th of 678 MPa. Alternatively, considering only the largest surface defect identified by CT ( √ area = 56 . 5 µ m and distance from the surface of 8 µ m), the e ff ective crack size is 23.8 µ m, resulting in an estimated fatigue limit of 664 MPa, which di ff ers from the previous estimate by only 2%. These investigations are meant to be preliminary and will be examined in more detail in a future study, which will systematically analyze the interaction between subsurface defects and the as-built surface under di ff erent surface finishes of materials produced by PBF-LB / M. This study investigates the method for estimating the maximum depth of the surface micronotches in Ti6Al4V sam ples built in PBF-LB / M with the surface in the as-built condition using Extreme Value Statistics (EVS), comparing the EVS predictions with the actual maximum depth of the entire surface. A sampling size greater than 10 provides stable estimates of the surface micronotches yielding less than 5% deviation from the actual measured values. The findings confirm the reliability of the method for predicting fatigue-relevant surface characteristics by optical pro filometry. X-ray computed tomography data revealed subsurface defects with sizes comparable to roughness-induced notches, but their influence on fatigue limit estimation was marginal (2% di ff erence). These preliminary results sup port the use of EVS-based roughness analysis as a predictive tool and lay the foundation for future studies addressing the interaction between surface finish and subsurface defects. 5. Conclusions Atzori, B., Lazzarin, P., Meneghetti, G., 2003. Fracture mechanics and notch sensitivity. Fatigue & Fracture of Engineering Materials & Structures 26, 257–267. doi: 10.1046/J.1460-2695.2003.00633.X . Atzori, B., Lazzarin, P., Meneghetti, G., 2005. A unified treatment of the mode I fatigue limit of components containing notches or defects. International Journal of Fracture 2005 133:1 133, 61–87. doi: 10.1007/S10704-005-2183-0 . Barricelli, L., Patriarca, L., du Plessis, A., Beretta, S., 2023. Orientation-dependent fatigue assessment of ti6al4v manufactured by l-pbf: Size of surface features and shielding e ff ect. International Journal of Fatigue 168, 107401. doi: 10.1016/J.IJFATIGUE.2022.107401 . Bonato, N., Zanini, F., Carmignato, S., 2024. Prediction of spatter-related defects in metal laser powder bed fusion by analytical and machine learning modelling applied to o ff -axis long-exposure monitoring. Additive Manufacturing 94, 104504. doi: https://doi.org/10.1016/j. addma.2024.104504 . Diaz, A., 2019. 16 - surface texture characterization and optimization of metal additive manufacturing-produced components for aerospace applications, in: Froes, F., Boyer, R. (Eds.), Additive Manufacturing for the Aerospace Industry. Elsevier, pp. 341–374. doi: https: //doi.org/10.1016/B978-0-12-814062-8.00018-2 . du Plessis, A., Beretta, S., 2020. Killer notches: The e ff ect of as-built surface roughness on fatigue failure in AlSi10Mg produced by laser powder bed fusion. Additive Manufacturing 35, 101424. doi: https://doi.org/10.1016/j.addma.2020.101424 . Leuders, S., Tho¨ne, M., Riemer, A., Niendorf, T., Tro¨ster, T., Richard, H.A., Maier, H.J., 2013. On the mechanical behaviour of titanium alloy TiAl6V4 manufactured by selective laser melting: Fatigue resistance and crack growth performance. International Journal of Fatigue 48, 300–307. doi: 10.1016/J.IJFATIGUE.2012.11.011 . Mioli, F., Bonato, N., Carmignato, S., Savio, E., 2024. Development of a multi-configuration support for the comparison of X-ray computed tomography and optical profilometry surface texture measurements, in: euspen’s 24th International Conference & Exhibition, Dublin, IE, June 2024. Mioli, F., Bonato, N., Rigon, D., Meneghetti, G., Carmignato, S., Savio, E., 2025. Accurate comparison of optical and X-ray computed tomography surface texture measurements on as-built additive manufactured test specimens to improve the accuracy of fatigue life predictions, in: euspen’s 25th International Conference & Exhibition, Zaragoza, ES, June 2025. Murakami, Y., 2019. Metal fatigue: E ff ects of small defects and nonmetallic inclusions . Nakatani, M., Masuo, H., Tanaka, Y., Murakami, Y., 2019. E ff ect of Surface Roughness on Fatigue Strength of Ti-6Al-4V Alloy Manufactured by Additive Manufacturing. Procedia Structural Integrity 19, 294–301. doi: 10.1016/J.PROSTR.2019.12.032 . Acknowledgements This study was carried out within the MICS (Made in Italy—Circular and Sustainable) Extended Partnership and re ceived funding from the European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR)—MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.3—D.D. 1551.11-10-2022, PE00000004). References