PSI - Issue 8

Gianni Nicoletto / Procedia Structural Integrity 8 (2018) 184–191 Author name / Structural Integrity Procedia 00 (2017) 000–000

191

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5. Conclusions Widespread acceptance of the SLM technology for load-bearing applications is challenged by the high costs involved in material, process and part qualification, because metal powders are expensive, the SLM production systems are expensive and fatigue testing had to investigate many influence factors. Here a non-standard (i.e. miniature) specimen geometry especially developed for SLM metals was applied to efficiently generate new knowledge in the fatigue behavior of DMLS Ti6Al4V. The following conclusions were reached:  the mini specimen test methodology yields fatigue results coherent with those obtained with standard rotating bending specimens;  the influence of surface quality on fatigue was investigated and the fatigue strength of i) as-built state, ii) after manual grinding and ii) after surface machining determined and compared;  the influence of notch and material directionality on fatigue strength was quantified for the first time through the definition of a notch fatigue factor with respect the unnotched as-built fatigue strength: a stress applied parallel to material build direction has a milder notch effect than a stress applied perpendicular to material build. Acknowledgements The company BEAM-IT srl, Fornovo Taro, Italy is acknowledged with thanks for the on-going cooperation in metal AM characterization and for specimen production. References Bača, A., Konečná, R., Nicoletto, G., Kunz, L., 2016. Influence of build direction on the fatigue behaviour of Ti6Al4V alloy produced by direct metal laser sintering. Materials Today: Proceedings 3, 921-924. Bandyopadhyay, A., Bose, A., 2016. Additive manufacturing: Additive manufacturing technologies of metals using powder-based technology. Taylor & Francis Group: Boca Raton, pp. 377. Edwards P., Ramulu M., 2014. Fatigue performance evaluation of selective laser melted Ti–6Al–4V, Mater. Sci. Eng., A598, 327–337. Kahlin M., H. Ansell, J.J. Moverare, (2017). Fatigue behaviour of notched additive manufactured Ti6Al4V with as-built surfaces, International Journal of Fatigue 101, 51–60 Konečná, R., Nicoletto. G., Bača, A., Kunz, L., 2017. Metallographic characterization and fatigue damage initiation in Ti6Al4V alloy produced by direct metal laser sintering. Materials Science Forum, 891, 311-316. Juvinall, R., Marshek, K.M., 2012. Fundamentals of Machine Component Design, New York: John Wiley. Li, P., Warner, D.H., Fatemi, A., Phan, N., 2016. Critical assessment of the fatigue performance of additively manufactured Ti–6Al–4V and perspective for future research, International Journal of Fatigue 85, 130–143 Mower, T. M., Long, M. J., 2016. Mechanical behavior of additive manufactured, powder-bed laser-fused materials. Materials Science and Engineering A651, 198-213. Nicoletto, G., 2016. Anisotropic high cycle fatigue behavior of Ti-6Al-4V obtained by powder bed laser fusion. International Journal of Fatigue 94, 255-262. Rafi, H. K., Karthik, N. V., Gong, H., Starr, T. L., Stucker, B. E., 2013. Microstructures and mechanical properties of Ti6Al4V parts fabricated by selective laser melting and electron beam melting, J. of Materials Engineering and Performance 22, 3872-3883. Ray, (2017). http://www.disruptivemagazine.com/opinion/calculating-cost-additive-manufacturing. Seifi, M., Salem, A., Beuth, J., Harrysson, O., Lewandoski, J.J., 2016. Overview of Materials Qualification Needs for Metal Additive Manufacturing, JOM, 68(3). Shiomi, M., Osakada, K., Nakamura, K., Yamashita, T., Abe, F., 2004. Residual stress within metallic model made by selective laser melting process. Journal of the CIRPAnnals - Manufacturing Technology, 53, 195-198. Simonelli, M., Tse, Y.Y., Tuck, C., 2012. Further understanding of Ti-6Al-4V selective laser melting using texture analysis. In 23rd Annual International Solid Freeform Fabrication Symposium, 480-491. Wycisk, E., Solbach, A., Siddique, S., Herzog, D., Walther, F., Emmelmann, C., 2014.Effects of defects in laser additive manufactured Ti–6Al– 4V on fatigue properties. Phys. Proc. 56, 371–378.