Additively manufactured (AM) lattice structures are designed and optimized while accounting for the effects of manufacturing-induced material orthotropy, the resolution limitations of AM, and multiphysics (structural and thermal) loading conditions. A model is formulated for general 3D orthotropy in each member of an AM lattice structure, with principal material coordinates associated with the AM build direction. This model is used within a bi-level design optimization strategy to simultaneously optimize the radius of each lattice member and the manufacturing build direction. Design study results illustrate the importance of accounting for material anisotropy in the design of AM lattice structures and the benefits of simultaneously optimizing the lattice and the manufacturing build direction. To account for AM resolution limitations, a model-based approach is implemented that accounts for geometrical tolerances while minimizing the geometric differences between the as-designed structure and the as-manufactured one. The influences of both material orthotropy and manufacturing resolution are studied and compared, demonstrating that both printing direction and process resolution play crucial roles in guaranteeing the performance and manufacturability of the as-manufactured lattice structure. For lattice design under multiphysics fields, a method is proposed to generate lattice structure designs under multiphysics loading, including stress, heat conduction, and heat convection. For a given set of loading and boundary conditions, a lattice trajectory is generated with an orientation vector selection algorithm based on the principal vectors of each field. Considering the design bias for a given physics field, weighting factors are assigned for each field to generate the lattice layout. A set of design studies are conducted to demonstrate the impact of different combinations of weighting factors on the lattice layout. It is shown that the proposed approach is capable of generating efficient lattice designs that represent effective trade-offs between mechanical and thermal load-carrying capabilities.
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