Study On Additive Manufacturing Oriented Topology Optimization

Topology optimization(TO)is an efficient technique that capable of finding the best distribution of materials given optimization objectives and constraints.However,the designs obtained by TO are usually geometrically complex,which cannot be fabricated easily by conventional manufacturing methods.As a rapidly evolving manufacturing technique,additive manufacturing can realize free-form manufacturing of complex shapes and structures.Based on this background,in view of the characteristics and shortcomings of additive manufacturing process,this paper studies the additive manufacturing oriented topology optimization method to promote the effective integration of additive manufacturing and topological optimization method.First,the basic principles of the finite element methodare reviewed.The sensitivity analysis of a structural responses such as the compliance,the natural frequency and so on are derived when one element is deleted.It lays a theoretical foundation for the research of topology optimization theory and method.On the basis of studying the problems and shortcomings of traditional topology optimization methods,this article presents a density-constrained topology optimization(DCTO)method.This method adopts a linear material interpolation scheme without penalization.Basic idea of the new method is first to find the optimal structural "thickness"(material density)distribution by the optimality criterion method,and then sequential constraints are applied on the material density distribution through a floating projection function to push it towards a 0/1 distribution step by step.This method is fundamentally different from other methods?It can obtain clear and smooth structural topology,and can avoid the difficulties in selecting artificial material interpolation schemes.Based on the previous work,the element refined DCTO method is proposed to generate a clearer and smoother boundary of topology.In the element refined designs,each element is further divided into several grid points,and then the boundary is formed based on the 0/1 design at those grid points executed by the level-set method.As the number of grid points is much more than the number of elements,a clearer and smoother topological boundary can be formed.Thus,a more precise CAD model can be constructed.Aiming at the problem of too much support in 3D printing process,the additive manufacturing oriented DCTO method is proposed by simulating the typical additive manufacturing process and adopting layer by layer filtering.By controlling the overhang angle of the topology with 45 °,a self-supporting topology design is obtained,which can reduce the manufacturing cost of 3D printing and simplify the post-treatment.Finally,the designs are printed,and the effectiveness of the proposed method is verified by comparing the results with or without overhang angle constraint.