Strength and stiffness-based structural topology optimization considering process-induced material anisotropy for additive manufacturing

This work addresses a challenging problem in high-performance design for additive manufacturing (AM): considering AM process-induced material anisotropy in structural topology optimization with stiffness and strength requirements. A novel formulation for minimizing anisotropic failure strength with stiffness and material volume constraints is proposed, by integrating a newly constructed AM process-related anisotropic material model. Specifically, the building direction angle (as a key design variable) is introduced into the orthogonal anisotropy material model to quantify the AM process-induced anisotropic mechanical properties. A tailored anisotropic failure index is developed as the minimization objective to achieve high-performance design. And, a strength ratio-based Hoffman failure function is proposed to avoid the locally over-conservative design caused by the traditional non-homogeneous failure criterion. In addition, the P-norm-based global aggregation and error correction techniques are employed to obtain reasonable strength measurement. The adaptive reduction strategy for the feasible region of angle variables is applied to address the convergence difficulties caused by the periodicity of trigonometric functions related to angle variables. Moreover, the sensitivities related to density and angle variables are derived in detail. Typical numerical examples illustrate the proposed methods. Due to the rational utilization of the AM process-induced material anisotropy, the proposed algorithm significantly improves structural strength while ensuring structural stiffness, and the optimization process also becomes easy to converge.