Apparent properties of porous support structure with imperfections in metal additive manufacturing

In the laser powder bed fusion (L-PBF) additive manufacturing (AM) of metals, support structure is necessary for overhang shaped components. This support is porous with periodic 2D lattice microstructure. The purpose of this paper is to predict numerically the apparent properties of porous support made by titanium alloy, Ti-6Al-4V. One of the problems involved in L-PBF AM is the geometrical imperfections, which are also seen in the microstructure of the support. Micro-CT imaging revealed the variation in strut width and the disconnections. They were parameterized and statistically measured for two cases with different design parameter that determines the density of the 2D lattice microstructure. Based on the statistically measured data, three probabilistic microstructure models were generated per one design parameter. The asymptotic homogenization method was applied to calculate the apparent Young's moduli, shear moduli and thermal conductivities assuming orthotropic material model. The calculated results were compared with those based on the CAD data without imperfections. Finally, the apparent properties were correlated with the design parameter so that they can be used in the process simulation in the design phase before manufacturing.