PSI - Issue 53

6

Camilla Ronchei et al. / Structural Integrity Procedia 00 (2023) 000 – 000

Camilla Ronchei et al. / Procedia Structural Integrity 53 (2024) 112–118

117

Conservative

Conservative

(a)

(b)

10 7

10 7

EXPERIMENTAL LIFETIME, N exp [cycles] 10 4 10 3 10 4 10 5 10 6

EXPERIMENTAL LIFETIME, N exp [cycles] 10 4 10 3 10 4 10 5 10 6

Axial R=-1 Torsional R=-1 Torsional R=0. 1

Axial R=-1 Torsional R=-1 Torsional R=0. 1

THEORETICAL LIFETIME, N f [cycles] 10 3 10 5 10 6 10 7

THEORETICAL LIFETIME, N f [cycles] 10 3 10 5 10 6 10 7

w  and w  ; (b)

, 1 af  − and

, 1 af  − .

Fig. 5. Comparison between theoretical and experimental fatigue lifetime determined by employing as fatigue limits: (a)

5. Conclusions In the present paper, a novel analytical procedure has been applied to some experimental data of the literature related to AM AlSi10Mg specimens, characterised by intrinsic defects and subjected to cyclic loading. The procedure involves the use, firstly, of the Kitagawa-Takahashi diagram for the fatigue limit calculations and, then, of the fatigue criterion by Carpinteri et al for the fatigue strength assessment and lifetime estimation. In particular, the theoretical results, obtained by considering both the experimental fatigue limits and the computed ones, have been compared to the experimental data: - for fatigue strength assessment, the experimental fatigue failure and run-out conditions are correctly predicted by using w  and w  , whereas the present procedure in terms of , 1 af  − and , 1 af  − is not capable to correctly capture many experimental fatigue failures; - for fatigue lifetime estimation, the present procedure in terms of , 1 af  − and , 1 af  − provides non-conservative results, whereas it is possible to achieve better estimations by employing w  and w  , with the results falling mostly within the scatter band 3. All the above remarks support the conclusion that the present procedure can be considered as a promising engineering tool for fatigue design of AM metallic components. However, more research work needs to be done in order to safely extend its use to other defective AM metals subjected to more complex loading conditions. Beretta, S., Murakami, Y., 2000. SIF and threshold for small cracks at small notches under torsion. Fatigue & Fracture of Engineering Materials & Structures 23, 97-104. Beretta, S., Romano, S., 2017. A comparison of fatigue strength sensitivity to defects for materials manufactured by AM or traditional processes. International Journal of Fatigue 94, 178-191. Carpinteri, A., Ronchei, C., Scorza, D., Vantadori, S., 2015. Critical plane orientation influence on multiaxial high-cycle fatigue assessment. Physical Mesomechanics 18, 348-354. Hu, Y.N., Wu, S.C., Wu, Z.K., Zhong, X.L., Ahmed, S., Karabal, S., Xiao, X.H., Zhang, H.O., Withers, P.J., 2020. A new approach to correlate the defect population with the fatigue life of selective laser melted Ti-6Al-4V alloy. International Journal of Fatigue 136, Article No. 105584. Kitagawa, H., Takahashi, S., 1976. Applicability of fracture mechanics to very small cracks or the cracks in the early stage. In: Proceedings of 2nd International Conference on Mechanical Behaviour of Materials. Boston, pp. 627 – 631. Murakami, Y., 1994.Inclusion rating by statistics of extreme values and its application to fatigue strength prediction and quality control of materials. Journal of Research of the National Institute of Standards and Technology 99, 345-351. Murakami, Y., 2002. Metal Fatigue: Effects of Small Defects and Nonmetallic Inclusions. Elsevier Science Ltd., Oxford. Romano, S., Brückner-Foit, A., Brandão, A., Gumpinger, J., Ghidini, T., Beretta, S., 2018. Fatigue properties of AlSi10Mg obtained by additive manufacturing: defect-based modelling and prediction of fatigue strength. Engineering Fracture Mechanics 187, 165-189. Sanaei, N., Fatemi, A., 2020. Analysis of the effect of internal defects on fatigue performance of additive manufactured metals. Materials Science and Engineering: A 785, Article No. 139385. Sanaei, N., Fatemi, A., 2021. Defects in additive manufactured metals and their effect on fatigue performance: a state-of-the-art review. Progress in Materials Science 117, Article No. 100724. References