PSI - Issue 37

Felix Stern et al. / Procedia Structural Integrity 37 (2022) 153–158 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Conclusions The influence of artificial internal defect size on the fatigue behavior of the austenitic steel 316LVM was clearly shown. However, defects with a size of √area ≤ 300 µm did not cause failure but crack initiation was found to be at the surface of the specimen. It was tried to describe the behavior by a defect-based model in terms of a Kitagawa Takahashi diagram and an extension by El Haddad et al. The assumed stress intensity threshold taken from literature for PBF-LB/M 316L steel resulted in an intrinsic crack length of a 0 = 54 µm which does not hold true for at least the investigated internal defects. The 316LVM steel did show defect tolerance which was much higher than calculated by the model. For that, the influence of this behavior in terms of a pseudo Hall-Petch effect or the present environment inside of internal defects has to be further investigated. Acknowledgements The authors thank the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) for its financial support within the research project No. 372290567 “Mechanism -based assessment of the influence of powder production and process parameters on the microstructure and the deformation behavior of SLM-compacted C + N steels i n air and in corrosive environments” (WA 1672/30-1) and No. 379213719 “Damage tolerance evaluation of electron beam melted cellular structures by advanced characterization techniques” (WA 1672/32-1). The PBF-LB/M processes were funded by the Science Support Center of the University of Duisburg-Essen and its internal funding program for excellent young researchers. References [1] Herzog, D., Seyda, V., Wycisk, E., Emmelmann, C., 2016. Additive manufacturing of metals. Acta Materialia 117, 371 – 392. [2] Günther, J., Leuders, S., Koppa, P., Tröster, T., Henkel, S., Biermann, H., Niendorf, T., 2018. On the effect of internal channels and surface roughness on the high-cycle fatigue performance of Ti-6Al-4V processed by SLM. Materials & Design 143, 1 – 11. [3] Stern, F., Kleinhorst, J., Tenkamp, J., Walther, F., 2019. Investigation of the anisotropic cyclic damage behavior of selective laser melted AISI 316L stainless steel. Fatigue & Fracture of Engineering Materials & Structures 42, 2422 – 2430, 11. [4] Solberg, K., Guan, S., Razavi, S., Welo, T., Chan, K., Berto, F., 2019. Fatigue of additively manufactured 316L stainless steel: The influence of porosity and surface roughness. Fatigue & Fracture of Engineering Materials & Structures 42, 2043 – 2052, 9. [5] 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. [6] Tenkamp, J., Awd, M., Siddique, S., Starke, P., Walther, F., 2020. Fracture – mechanical assessment of the effect of defects on the fatigue lifetime and limit in cast and additively manufactured aluminum – silicon alloys from HCF to VHCF regime. Metals 10, 943, 7. [7] Murakami, Y., 2019. Metal fatigue. Academic Press, London. [8] Kotzem, D., Kleszczynski, S., Stern, F., Elspaß, A., Tenkamp, J., Witt, G., Walther, F., 2021. Impact of single structural voids on fatigue properties of AISI 316L manufactured by laser powder bed fusion. International Journal of Fatigue 148, 106207. [9] Kitagawa, H., Takahashi, S., 1976. Applicability of fracture mechanics to very small cracks or the cracks in the early stage. In: Proceedings of the Second International Conference on Mechanical Behavior of Materials, American Society for Metals, 627 – 631. [10] Andreau, O., Pessard, E., Koutiri, I., Peyre, P., Saintier, N., 2021. Influence of the position and size of various deterministic defects on the high cycle fatigue resistance of a 316L steel manufactured by laser powder bed fusion. International Journal of Fatigue 143, 105930. [11] El Haddad, M., Smith, K., Topper, T., 1979. Fatigue crack propagation of short cracks. Journal of Engineering Materials and Technology 101, 42 – 46, 1. [12] Riemer, A., Leuders, S., Thöne, M., Richard, H., Tröster, T., Niendorf, T., 2014. On the fatigue crack growth behavior in 316L stainless steel manufactured by selective laser melting. Engineering Fracture Mechanics 120, 15 – 25. [13] Liu, L., Ding, Q., Zhong, Y., Zou, J., Wu, J., Chiu, Y.-L., Li, J., Zhang, Z., Yu, Q., Shen, Z., 2018. Dislocation network in additive manufactured steel breaks strength – ductility trade-off. Materials Today 21, 354 – 361, 4. [14] Pham, M., Dovgyy, B., Hooper, P., 2017. Twinning induced plasticity in austenitic stainless steel 316L made by additive manufacturing. Materials Science and Engineering: A 704, 102 – 111. [15] Jesus, J. de, Borges, M., Antunes, F., Ferreira, J., Reis, L., Capela, C., 2021. A novel specimen produced by additive manufacturing for pure plane strain fatigue crack growth studies. Metals 11, 433, 3.