PSI - Issue 68

Giuseppe Macoretta et al. / Procedia Structural Integrity 68 (2025) 974–980 G. Macoretta et al. / Structural Integrity Procedia 00 (2025) 000–000

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region, specimens tested at stress levels below those causing before 0.08 million cycles did not fail until the run-out threshold of 10 million cycles. The fatigue crack originated from the surface region for all the specimens. Multiple crack onset sites were detected for the notched specimens, due to the interaction between the nominal notch and the local surface irregularities. The fatigue notch sensitivity was found to be 0.13 for the blunter notches ( k t 1.5 and 2), while 0.22 for the sharper one ( k t 3.5). This behavior can be rationalized considering that the L-PBF process resulted in producing a local notch radius that is similar to the nominal one for the k t 1.5 and 2 notches, while it is significantly more severe for the k t 3.5 specimen that presented a nominal radius of 0.21 mm. Acknowledgments The authors gratefully acknowledge Mr. Roberto Minelli for the mechanical tests, Mr. Flavio Antonelli for the specimen machining, and Eng. 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