Multi-scale Topology Optimisation with Overheating Control for Laser Powder Bed Fusion
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In this study, a novel multi-scale approach for topology optimisation with control of overheating during Laser Powder Bed Fusion process is presented. Such a physics-based constraint for topology optimisation for additive manufacturing was previously published as a mono-scale variant. The presented algorithm is based on the homogenisation of the body-centred cubic (BCC) lattice cell, which allows the intermediate densities to be interpreted with lattice structures with varying relative densities. Homogenised modulus of elasticity and thermal conductivity are used as material interpolation in the density-based topology optimisation. Furthermore, the homogenised properties are complemented by the Heaviside function to include manufacturing limits in the form of minimum and maximum relative density. Both fabrication limits namely the minimum feature size and powder accessibility for cleaning are experimentally determined for the Ti6Al4V alloy and the BCC lattice unit cell size of 5 mm. The multi-scale approach can fulfil the overheating constraint at par with the previously published mono-scale algorithm. Additionally, it offers lower compliance compared to the mono-scale variant and also to the algorithm that optimises the geometry for additive manufacturing based only on the geometric overhang.