Mechanical Properties of Ti-6Al-4V Selectively Laser Melted Parts with Body-Centred-Cubic Lattices of Varying cell size

Maskery, I.; Aremu, A.O.; Simonelli, M.; Tuck, C.; Wildman, R.D.; Ashcroft, I.A.; Hague, R.J.M.

Abstract

Significant weight savings in parts can be made through the use of additive manufacture (AM), a process which enables the construction of more complex geometries, such as functionally graded lattices, than can be achieved conventionally. The existing framework describing the mechanical properties of lattices places strong emphasis on one property, the relative density of the repeating cells, but there are other properties to consider if lattices are to be used effectively. In this work, we explore the effects of cell size and number of cells, attempting to construct more complete models for the mechanical performance of lattices. This was achieved by examining the modulus and ultimate tensile strength of latticed tensile specimens with a range of unit cell sizes and fixed relative density. Understanding how these mechanical properties depend upon the lattice design variables is crucial for the development of design tools, such as finite element methods, that deliver the best performance from AM latticed parts. We observed significant reductions in modulus and strength with increasing cell size, and these reductions cannot be explained by increasing strut porosity as has previously been suggested. We obtained power law relationships for the mechanical properties of the latticed specimens as a function of cell size, which are similar in form to the existing laws for the relative density dependence. These can be used to predict the properties of latticed column structures comprised of body-centred-cubic (BCC) cells, and may also be adapted for other part geometries. In addition, we propose a novel way to analyse the tensile modulus data, which considers a relative lattice cell size rather than an absolute size. This may lead to more general models for the mechanical properties of lattice structures, applicable to parts of varying size.

Citation

Maskery, I., Aremu, A., Simonelli, M., Tuck, C., Wildman, R., Ashcroft, I., & Hague, R. (2015). Mechanical Properties of Ti-6Al-4V Selectively Laser Melted Parts with Body-Centred-Cubic Lattices of Varying cell size. Experimental Mechanics, 55(7), 1261-1272. https://doi.org/10.1007/s11340-015-0021-5

• Journal Article Type: Article
• Acceptance Date: Apr 1, 2015
• Online Publication Date: Apr 24, 2015
• Publication Date: 2015-09
• Deposit Date: Feb 25, 2016
• Publicly Available Date: Feb 25, 2016
• Journal: Experimental Mechanics
• Print ISSN: 0014-4851
• Electronic ISSN: 1741-2765
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 55
• Issue: 7
• Pages: 1261-1272
• DOI: https://doi.org/10.1007/s11340-015-0021-5
• Keywords: Selective laser melting, Lattice, Titanium alloy, Additive manufacture, Lightweight structures
• Public URL: https://nottingham-repository.worktribe.com/output/982394
• Publisher URL: http://link.springer.com/article/10.1007%2Fs11340-015-0021-5
• Additional Information: This is a post-peer-review, pre-copyedit version of an article published in Experimental Mechanics. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11340-015-0021-5; ; Copyright Society for Experimental Mechanics 2015