Axisymmetric structural optimization design and void control for selective laser melting
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Additive manufacturing processes, of which Selective Laser Melting (SLM) is one, provide an increased design freedom and the ability to build structures directly from CAD models. There is a growing interest in using optimization methods to design structures in place of manual designs. Three design optimization problems were addressed in this paper. The first related to axisymmetric structures and the other two addressing important design constraints when manufacturing using SLM. These solutions were developed and applied to a case study of a turbine containment ring. Firstly, many structural components such as a turbine containment ring are axisymmetric while they are subjected to a non-axisymmetric load. A solution was presented in this paper to generate optimized axisymmetric designs for a problem in which the mechanical model was not axisymmetric. The solution also worked equally well for generating a prismatic geometry with a uniform cross section, requiring no change in the procedure from axisymmetric designs to achieve this. Secondly, the SLM process experiences difficulties manufacturing structures with internal voids larger than a certain upper limit. A method was developed that allowed the designer to provide a value for this upper limit to the optimization method which would prevent the generation of internal voids larger than this value in any optimized design. The method calculated the sizes of all the voids and did not increase their size once they reached this limit. It was also aware of voids near each other, providing a minimum distance between them. Finally, in order to remove the metal powder, that fills the internal voids of structures built using SLM to reduce unnecessary weight, a method was developed to build paths to join the internal voids created during the optimization process. It allowed the analyst to nominate suitable path entrance locations from which powder could be removed, then found the shortest path connecting all voids and these locations. For axisymmetric structures it also distributed this path around the circumference to avoid generating weak points.
KeywordsAxisymmetric structure Void control Bi-directional evolutionary structural optimization Additive manufacturing
Funding for this research was provided by Microturbo, a member of the Safran group. Computational resources were provided by the Australian Government through the National Computational Infrastructure.
Brian G. Falzon acknowledges the financial support of Bombardier and the Royal Academy of Engineering. X Wu and W Yan acknowledge the support of Australian Research Council through the ITRH project IH130100008 and the support of the Australian Science and Industry Endowment Fund through the SIEF project RP04-153 (Aero-Engine).
- ASM International (1967) Inconel Alloy 625. Alloy Digest.Google Scholar
- Brackett D, Ashcroft I, Hague R (2001) Topology optimization for additive manufacturing. In: Twenty second solid Freeform Fabrication (SFF) Symposium. University of Texas, Austin, pp 348–362Google Scholar
- Brooks W, Sutcliffe C, Cantwell W, Fox P, Todd J, Mines R (August 2005) Rapid design and manufacture of ultralight cellular materials. In: Sixteenth solid Freeform Fabrication (SFF) Symposium. University of Texas, Austin, pp 231–241Google Scholar
- Haber, R.B., Jog, C.S., and Bendsøe, M.P. (1996) A new approach to variable-topology shape design using a constraint on perimeter. Struct Optim, 11(1):1–12, doi: 10.1007/BF01279647.
- Haynes International Inc. (2001) Haynes 625 alloy. Technical Report H-3073D, Kokomo, Indiana 46904–9013 (USA). <http://www.haynesintl.com/pdf/h3073.pdf> Retrieved 28-Dec-2012.
- Hopkinson, N, Hague, RJM, and Dickens, PM (editors) (2006) Rapid manufacturing: an industrial revolution for the digital age. John Wiley & Sons, ltd, west Sussex PO19 8SQ, England, ISBN:978-0-4700-3399-9, doi: 10.1002/0470033991.
- Mayer RR, Kikuchi N, Scott RA (1996) Application of topological optimization techniques to structural crashworthiness. Int J Numer Methods Eng 39(8):1383–1403. doi: 10.1002/(SICI)1097-0207(19960430)39:8<1383::AID-NME909>3.0.CO;2-3 CrossRefzbMATHGoogle Scholar
- Samanta, A., Teli, M., and Singh, R.K. (2012) Surface integrity in laser assisted mechanical micro-machining of (LAMM) of Inconel 625. In Proceedings of international Conference on Micromanufacturing, Chicago, USA.Google Scholar
- Sorkine, O., Cohen-Or, D., Lipman, Y., Alexa, M., Rössl, C., and Seidel, H.-P. (2004) Laplacian surface editing. In Proceedings of the 2004 Eurographics/ACM SIGGRAPH Symposium on geometry processing, SGP’04, pages 175–184, New York, ACM.Google Scholar
- Special Metals Corporation (2006) Inconel alloy 625. Technical Report SMC-063, Huntington, WV 25705–1771 (USA). <http://www.specialmetals.com/documents/Inconel%20alloy%20625.pdf> Retrieved 30-Dec-2012.
- Stojanov D, Falzon BG, Wu X, Yan W (2016) Implementing a structural continuity constraint and a halting method for the topology optimization of energy absorbers. Struct Multidiscip Optim 54:429-448 doi: 10.1007/s00158-016-1451-0
- Watts DM, Hague RJ (2006) Exploiting the design freedom of rm. In: Seventeenth solid Freeform Fabrication (SFF) Symposium. University of Texas, Austin, pp 656–667Google Scholar
- Zhang, G., Li, L., Khandelwal, K. (2016) Topology optimization of structures with anisotropic plastic materials using enhanced assumed strain elements. Struct Multidiscip Optim. doi: 10.1007/s00158-016-1612-1