PSI - Issue 7

L. Boniotti et al. / Procedia Structural Integrity 7 (2017) 166–173

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L. Boniotti et al./ Structural Integrity Procedia 00 (2017) 000–000

6. Conclusions This work presents an experimental investigation of a typical AlSi10Mg micro-lattices, namely the BCC cell, produced by SLM process. DIC strain measurements were performed during a compressive test to capture the localization of strains on the real cell. Successively, 3D tomography was used to reconstruct the original geometry and a FE model of the idealized and real structures were developed. The main results from this activity are: • significant strain concentrations were measured by DIC on the surface of samples made by BCC cells that were subjected to compressive tests; • a first model was based on an ideal geometry of the sample derived from the design geometry: in this case struts are regular and very low strain localizations were detected • a FE model based on the real geometry derived from the micro-tomography was analyzed. In this model multiple strain concentrations were observed to be qualitatively similar (although lower) to the strain concentrations measured with DIC. The conclusion that can be presently drawn is that a model based on an ideal geometry does not permits to describe the real behavior of the printed lattice structure. Therefore estimates of the strength (both for static and fatigue loads) from a simplified geometry will likely be not precise enough for engineering calculations. Acknowledgement The authors would like to thank Thales Alenia Space, especially Mr. Luca Soli, for the supply of lattice specimens. The experiments are part of the activities carried out at the METAMAT-Lab of Politecnico di Milano. References [1] Park S.I., Rosen D.W., Choi S.K., Duty C.E., Effective mechanical properties of lattice material fabricated by material extrusion additive manufacturing, Additive Manufacturing, Volumes 1–4, October 2014, Pages 12–23. [2] Bartkowiak K., Ullrich S., Frick T., Schmidt M., New Developments of Laser Processing Aluminum Alloys via Additive Manufacturing Technique, Physics Procedia , Volume 12, Part A, 2011, Pages 393–401. [3] Brandl E., Heckenberger U., Holzinger V., Buchbinder D., Additive manufactured AlSi10Mg samples using Selective Laser Melting (SLM): Microstructure, high cycle fatigue, and fracture behavior, Mater. Des. , vol. 34, pp. 159–169, 2012. [4] Rashed M.G., Ashraf M., Mines R.A.W., Hazell P.J., Metallic microlattice materials: A current state of the art on manufacturing, mechanical properties and applications, (2016), doi: 10.1016/j.matdes.2016.01.146. [5] Ashby M., Materials Selection in Mechanical Design (3rd ed.). Burlington, Massachusetts: Butterworth-Heinemann, 1999. [6] Arabnejad Khanoki S., Pasini D., Mechanical properties of lattice materials via asymptotic homogenization and comparison with alternative homogenization methods, International Journal of Mechanical Sciences , 77 (2013), 249–262. [7] Arabnejad Khanoki S., Pasini D., Multiscale design and multiobjective optimization of orthopedic hip implants with functionally graded cellular material, Journal of Biomechanical Engineering , march 2012, Vol. 134. [8] Arabnejad Khanoki S., Johnston R.B., Pura J.A., Singh B., Tanzer M., Pasini D., High-strength porous biomaterials for bone replacement: A strategy to assess the interplay between cell morphology, mechanical properties, bone ingrowth and manufacturing constraints, Acta Biomaterialia 30 (2016) 345–356. [9] Sutcliffe C., Brooks W., Cantwell W., Fox P., Todd J., and Mines R.A.W.,The rapid manufacture of micro hierarchical structures by selective laser melting. Proc. ICALEO 2005,Univ. of Liverpool, 2005. [10] Tsopanos S., Mines R.A.W., McKown S., Cantwell W.J., Shen Y., Brooks W., The influence of processing parameters on the mechanical properties of selectively laser melted stainless steel microlattice structures. J. Manuf. Sci. Eng . 132, 2010. [11] ASTM E1441-11, Standard Guide for Computed Tomography (CT) Imaging, 2011. [12] Material data sheet, EOS Aluminium AlSi10Mg for EOSINT M 270, EOS GmbH, Vol. 90110024, 2011. [13] Mazur M., Leary M., McMillan M., Sun S., Shidid D., Brandt M., Mechanical Properties of Ti6Al4V and AlSi12Mg. Lattice Structures Manufactured by Selective Laser Melting (SLM). Laser Additive Manufacturing 119 (2016). [14] Rehme O., Emmelmann C. Rapid manufacturing of lattice structures with selective laser melting. Proceedings of the SPIE, Vol. 6107, 2006. [15] Van Hooreweder B., Kruth J., Advanced fatigue analysis of metal lattice structures produced by Selective Laser Melting, CIRP Annals - Manufacturing Technology , 66 (2017) 221–224. [16] De Krijger J., Rans C., Van Hooreweder B., Lietaert K., Pouran B., Zadpoor A., Effects of applied stress ratio on the fatigue behavior of additively manufactured porous biomaterials under compressive loading, Journal of the mechanical behavior of biomedical materials , 70 (2017) [17] Romano S., Brandão A., Gumpinger J., Gschweitl M., Beretta S., “Qualification of AM parts: Extreme value statistics applied to tomographic

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