Temperature Distribution Design of Functionally Graded Structure Based on Lattice Volume Fraction Distribution Optimization and Metal Additive Manufacturing

Abstract

In recent years, additive manufacturing (AM) has been used in industrial products for fabricating complex geometry. On the other hand, topological optimization is a suitable method for designing complex geometry. Therefore, there are many studies of combining AM and topological optimization these days. As a variant of topological optimization, density optimization of lattice structure is recently studied. The lattice structure is a characteristic one that includes void inside structure fabricated by AM. The designed model by topological optimization should be modified for a suitable structure for AM process. This research tried to use lattice volume fraction optimization for an industrial AM product. Firstly, we have developed a method of designing the lattice unit cell that its effective thermal conductivity is controlled by design variables. Effective thermal conductivity of lattice is calculated by homogenization method and finite element method (FEM). It was confirmed that the effective thermal conductivity changes depending on the size of the internal pores. Next, we consider the minimization problem of the surface temperature of the target domain. By lattice volume fraction optimization, the uniformity of the surface temperature of the target domain was improved. In addition, we fabricated test pieces of lattice and 3D example model by using selective laser melting additive manufacturing. The results showed that the error between the measurement and the analysis using the test piece was sufficiently small.