Simultaneous Optimization of Structural Topology and Print Direction for Additive Manufacturing Anisotropy

The rapid development of additive manufacturing (AM) technology provides an effective manufacturing method for complex designs generated by topology optimization. However, compared with traditional manufacturing methods, structures obtained by layer-by-layer printing process of AM usually exhibit anisotropic stiffness and strength properties, and the empirical selection of optimal structural print direction ignores the influence of process, which seriously limits the performance of AM structures. Therefore, a simultaneous optimization method of structural topology and print direction is proposed for the configuration and print angle design of anisotropic material model. The optimization convergence instability caused by coupling of design variables is improved to achieve the comprehensive performance improvement of AM products. Firstly, the anisotropic equivalent stiffness matrix based on material rotation angle and the strength constraint expression based on Tsai-Hill failure criterion are established. Secondly, the Lagrange multiplier is introduced to consider both structural compliance and failure coefficient constraint, and the sensitivity of the elemental design variables is derived. The weight hybrid method is developed to further derive the analytical solution of the material rotation angle. Finally, a series of numerical algorithms and key parameters updating strategies are used to stabilize the optimization process. The typical examples show that the proposed method can effectively obtain the optimized topology and optimal print direction. The final results significantly improve the stiffness while ensuring the structural strength, and the optimization process is easy to converge. © 2023 Editorial Office of Chinese Journal of Mechanical Engineering. All rights reserved.