Research On Multi-scale Topology Optimization Methods Of Self-supporting Structures For Additive Manufacturing

Structural topology optimization is an optimal design method for finding the optimum distribution of material in the design domain under given loads,constraints and boundaries.Additive manufacturing is a kind of material processing technology for rapid prototyping of solid parts in the way of accumulating material layer by layer.Nowadays,it is a trend to the process structures designed by topology optimization through additive manufacturing in industry.However,traditional topology optimization result is needed to add lots of support structures because of the large area of hangover domain,which causes the waste of material and time and the damage of structure quality.In practice,lattice structure has been proved of light weight,high quality and good manufacturability.Thus we research on multi-scale topology optimization methods of self-supporting structures for additive manufacturing,through which we can get the self-supporting structures consisting of massive lattice structure.The main work is as follows:Firstly,we present a topology optimization method for microstructure based on parametric level set method and energy-based homogenization method.In order to take advantage of traditional level set method and to avoid solving the complicated Hamilton-Jacobi partial differential equations,we introduce the parametric level set method based on the compactly supported radial basis function(CSRBF).Energy-based homogenization method is introduced aimed to overcome the difficulties of numerical homogenization method,including complicated prediction,time-consuming sensitivity analysis and complex numerical implementation.We establish the optimization model of microstructure based on the parametric level set method and energy-based homogenization method,calculate sensitivity analysis based on shape derivative.The optimization criterion method is used to solve the problems of microstructure with extreme physical performance and specific physical performance.Secondly,in consideration of advantages of self-supporting from lattice structure,we present a multi-scale topology optimization method of self-supporting structures for additive manufacturing.A two-stage topology optimization model is built.In the stage of macroscopic material layout optimization,we use SIMP model to obtain the macroscopic material density which is distributed freely in the design domain.In the stage of microstructure optimization,a clear and smooth boundary of microstructure is obtained by using topology optimization method for microstructure based on the results of macroscopic material distribution.Besides,we design self-supporting structures under the condition of single load,multiple load cases and passive elements.Thirdly,we present a multi-scale topology optimization method of self-supporting structures for additive manufacturing with multiphase material.A multi-scale topology optimization model is built adopting interpolation method of multiphase material,through which we can get multiphase self-supporting structures.A Michell structure example with three materials is presented to illustrate the advantages of the proposed method.Finally,we apply the proposed model and method in the design of Michell structure.We use the technology of Fused deposition modeling(FDM)and Stereolithography(SLA)to process it.The results show that through the proposed method we can get structure with selfsupporting capability.The self-supporting structures are easy to be processed by additive manufacturing and can take full use of the advantages of rapid prototyping.