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

By I. Maskery, A. Aremu, M. Simonelli, Christopher John Tuck, Ricky Wildman, Ian Ashcroft, Richard J. M. Hague. 2015

152 citations recorded by the source corpus.

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.

Subfields: Automotive Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/53b59a312c6415233ba03fd2f7774e29f5b60cef

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Citations in the corpus

Optimisation of functionally graded lattice structures using isostatic lines (2017, background): “These increased design freedoms offer the potential of achieving highly mass efficient designs by manufacturing cores with tailored cell geometries that are close to the idealised optimal solutions [4].”
Fractal scan strategies for selective laser melting of ‘unweldable’ nickel superalloys (2017, background): “A wide range of Ti [1, 2], Fe [3, 4], Ni [5, 6], and Al [7, 8] alloys have been processed via SLM, with near 100% bulk density and good mechanical performance.”
Understanding the effect of laser scan strategy on residual stress in selective laser melting through thermo-mechanical simulation (2016, background): “structures into components [5], and individual customisation, SLM has gained significant attention”
Design of graded lattice structure with optimized mesostructures for additive manufacturing (2018, methodology): “In general, most methods make use of lattices comprised of beams/trusses [4], which can work effectively at a low relative density with members of small bar diameters or wall thicknesses.”
Continuous graded Gyroid cellular structures fabricated by selective laser melting: Design, manufacturing and mechanical properties (2019, methodology): “It is worth noting that the empirical values of exponential m and n are used in this study, while researchers treated as varies and making the prediction more accurate [14,25].”