TOPOLOGICAL OPTIMIZATION DESIGN METHOD OF LAYER-WISE GRADED LATTICE STRUCTURES WITH HIGH LOAD-BEARING

With the rapid development of additive manufacturing technology, lattice structures have attracted extensive attention due to their excellent mechanical properties, such as high specific strength and high specific stiffness. However, the designs of lattice structures are mostly based on the assumption of uniform distribution, resulting in a relatively poor load-bearing capacity. This paper proposes a layer-wise graded lattice structure design method based on a topology optimization technology. Firstly, an explicit description model of lattice geometric configuration is established by using the level set function, and a shape interpolation technology is employed to generate the graded configurations of lattice cells. Secondly, a prediction model of macro effective mechanical property for these graded lattice cells is constructed based on the Kriging metamodel, achieving the essential relationship between the effective density of macro element and the effective mechanical property of micro lattice cell. Then, with the maximum stiffness of lattice structures as the optimization objective, the allowable material usage amount and structural system equilibrium equation as the constraint conditions, a layer-wise graded topology optimization model of lattice structures is established, which is solved numerically by using the OC algorithm. The numerical results indicate that the proposed method can realize the optimal layer-wise graded design of lattice structures, which not only fully improve the load bearing performance of lattice structures, but also ensure the geometric connectivity between different graded lattice cells. Finally, the quasi-static compression simulation analyses of the layer-wise graded lattice structures, the traditional uniform lattice structures and the linear graded lattice structures are carried out and discussed. The simulation results show that, compared with the traditional uniform lattice structures and the linear graded lattice structures, the loading capacity of the layer-wise graded lattice structures is significantly improved. The proposed method provides a theoretical reference for the design of high loading lattice structures.