Design optimization of thermally conductive support structure for laser powder-bed fusion process with part-scale thermal history

Abstract

Although there has been a substantial volume of research for mitigating the thermally-induced residual stress with the heat accumulation in powder bed fusion (PBF) process, it has been challenging to quantify, access, and optimize the heat dissipation at part-scale. Furthermore, a practical method of designing three-dimensional support with a reasonable index for evaluating inhomogeneous cooling is also of high importance for facilitating the process. In this study, an optimization methodology for designing a thermally conductive lattice support structure is proposed considering the layerwise heating and cooling in the PBF process. A part-scale numerical model with homogenized properties of lattice material is constructed using the temperature-thread multiscale modeling approach to simulate the transient temperature field in PBF process. The transient analysis model is then integrated into the lattice structure topology optimization (LSTO) with the equivalent static loads method (ESLM) based sensitivity analysis to derive the optimal density profile of the support. In particular, a novel concept of the normalized liquid lifetime contour is proposed to analyze the inhomogeneous cooling in PBF process at part-scale. The normalized liquid lifetime is also utilized to build an effective part-scale thermal load to significantly reduce the overall computational cost for the optimization process. The proposed framework is also validated through thermo-mechanical process analysis and experiment for a benchmark case of manufacturing a twin cantilever beam.