PSI - Issue 68

Ilia Nikitin et al. / Procedia Structural Integrity 68 (2025) 24–31

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I. Nikitin et al. / Structural Integrity Procedia 00 (2025) 000–000

5. Conclusion A new approach for designing selective laser melting (SLM) ingots is proposed. The predicted fatigue life is suggested as a key parameter for adjusting the laser beam power and scanning rate values. Based on the numerical solution of the non-linear heat conduction problem with a moving phase transition boundary, typical internal defects of the SLM microstructure are simulated. Non-melt zones lead to weak cohesion between neighboring material layers and can be simulated as areas with local deviations in elastic moduli (low values). Re-melt zones lead to phase trans formation, coarse platelet formation, and, therefore, to local strain incapability. Such zones can be simulated as areas with slightly elevated elastic moduli. The proposed approach allows linking the SLM parameters as input with the expected fatigue life as output. The simulation of fatigue life for the VHCF specimen containing the predicted types of defects shows the important role of not-melt zones. The fatigue life of specimens with non-melt zones can be up to 10 times shorter compared to the regular structure. The influence of the re-melt defects is lower due to the smaller deviation of elastic moduli. The predicted fatigue life for the specimen with re-melt defects is 1.5 times shorter than for the regular structure. Acknowledgements This work was supported by Russian Science Foundation, project № 23-19-00640. References Bathias, C., Paris, P., 2004. Gigacycle fatigue in mechanical practice. Dekker. New York., p. 328. Burago, N.G., Nikitin, I.S., Nikitin, A.D., Stratula B.A., 2024. Numerical Modeling of Fatigue Fracture Based on the Nonlocal Theory of Cyclic Damage. Mathematical Models and Computer Simulations 16, 655–666. Carpinteri, A., Spagnoli, A., Vantadori, S., 2011. Multiaxial fatigue assessment using a simplified critical plane-based criterion. International Journal of Fatigue 33, 969–976. Nikitin, A., Palin-Luc, T., Shanyavskiy, A., 2016. Crack initiation in VHCF regime on forged titanium alloy under tensile and torsion loading modes. International Journal of Fatigue 93, 318-325. Nikitin, A.D., Burago, N.G., Nikitin, I.S., Stratula, B.A., 2019. Algorithms for calculation damage processes. Frattura ed Integrità Strutturale 13, 212-224. Nikitin, I.S., Burago, N.G., Nikitin, A.D., 2022. Damage and fatigue fracture of structural elements in various cyclic loading modes. Mechanics of Solids 57, 1793–1803. Palin-Luc, T., Jeddi, D., 2018. The gigacycle fatigue strength of steels: a review of structural and operating factors. Procedia Structural Integrity 13, 1545-1553. Sakai, T., Nakagawa, A., Oguma, N., Nakamura, Y., Ueno, A., Kikuchi, S., Sakaida, A., 2016. A review on fatigue fracture modes of structural metallic materials in very high cycle regime. International Journal of Fatigue 93, 339‐351. Shanyavskiy, A.A., 2013. Mechanisms and modeling of subsurface fatigue cracking in metals. Engineering Fracture Mechanics 110, 350‐363. Smith, R.N., Watson, P., Topper, T.H., 1970. A stress-strain parameter for the fatigue of metals. Journal of Materials 5, 767–778. White, R.E., 1982. An enthalpy formulation of the Stephan problem. SIAM Journal of Numerical Analysis 19, 1129 – 1157.