Topology optimization of hybrid structures in additive manufacturing

Today, issues related to energy conservation or efficiency are an increasing field of study with the increasing global warming problems. Inefficient energy consumption is one of the main reasons for the increase of global warming problems. In this context, many engineering studies are carried out on energy conservation or efficiency. One of these studies is structural optimization studies to produce lighter designs. Topology and lattice structure optimizations are among these structural optimization studies.Topology and lattice structure optimizations are inherently complex structures. It is may not be possible to manufacture this complex structures using conventional manufacturing methods. As a result, designers impose manufacturability constraints on structural optimization studies, which reduces the efficiency of the optimization. With the development of additive manufacturing (AM) technologies, the efficiency of structural optimization studies has increased. It is possible to manufacture complex designs with AM technologies. Another important issue that affects the efficiency of structural optimization studies is that the material density remains constant throughout the design. Topology optimization with constant density reduces the mass reduction ratio in the design. Especially in topology optimization studies, an optimization study with variable density within the design increases the efficiency of the optimization even more. Adding lattice structures to topology optimization studies provides variable density optimization. In this thesis, the optimization of a hybrid structure including topology and lattice structure optimization according to AM is carried out by finite element analysis (FEA) and experimentally. In order to obtain the hybrid structure, two separate structural optimization studies were performed on the solid topology and lattice structure using FEA. In the optimization studies, the lightest optimal structures were determined for the yield strength of the AlSi10Mg material. Optimal lattice structures were added to the low stress intermediate density regions of the solid topology design. Thus, a hybrid variable density structure optimization study was performed, which is more light than topology optimization. The hybrid structure optimization approach proposed in the thesis was applied to a helicopter main landing gear part. In addition, the energy absorption optimization of lattice structures and the effect of heat treatment on structure optimization were also investigated using FEA. The specimens of solid topology, lattice and hybrid structure designs with optimum parameters obtained from the FEA study were manufactured from AlSi10Mg material by selective laser melting (SLM) method, one of the AM technologies. Mechanical tests and metallographic studies were carried out on the manufactured specimens and the results compared with FEA and the literature.