Authors: I Maskery AO Aremu M Simonelli C Tuck RD Wildman IA Ashcroft RJM Hague
Publish Date: 2015/04/24
Volume: 55, Issue: 7, Pages: 1261-1272
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 bodycentredcubic 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 sizeWe would like to thank Sean Smith Ravi Aswathanarayanaswamy Hossein SheykhPoor and various teams at Renishaw Plc for the provision of the test specimens and continued support in our collaborative projects Thanks also to Mark East Mark Hardy and Joe White technicians of the Additive Manufacture and 3D Printing Research Group at Nottingham Funding was provided by Innovate UK formerly the UK Technology Strategy Board TSB
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