Structural topology optimization considering material anisotropy induced by additive manufacturing processes

Abstract

This work proposes a structural topology optimization method to consider material anisotropy induced by additive manufacturing processes. To quantify the relationship between manufacturing processes and mechanical properties of formed materials, the building direction angle is introduced into a transversely isotropic material model as a design variable. An anisotropic material model related to the building direction is thus established. A parallel optimization framework for structural topology and building direction is proposed by extending the classical compliance minimization formulation. And, to be applicable to gradient-based optimization algorithms, sensitivities related to density and angle variables are derived separately. Especially, to overcome the convergence difficulties caused by the periodic angle variables, an adaptive reduction strategy for the feasible region of angle variables is proposed. Typical numerical examples verify the rationality of the proposed method. The results show that the building direction related process-induced anisotropy significantly affects the optimized structural properties. The fluctuation of the trigonometric functions related to the angle variables would lead to obvious iteration oscillation in the optimization process, which makes the optimization difficult to converge. The proposed adaptive reduction strategy is proven effective in addressing this challenge. Besides, typical numerical properties of the co-optimization of structural topology and building direction are also revealed.