Topology Optimization Method Of Additive Manufacture Structures With Surface Layer Heterogeneity And Uncertainty Considered

The development of the high-end equipment manufacturing industry requires the combination of new design methods and manufacturing technologies to achieve design and manufacturing integration.Topology optimization as a function-driven innovative design method doesn't depend on the initial configuration and can provide novel and high-performance structures.Additive manufacturing technology is based on CAD model of the structure,and it accumulates the material manufacturing structure layer by layer under computer control.It can be used to prepare complex structures with complicated geometrical configuration,complicated material distribution,complicated hierarchical relationships,and complicated functional composition,which can maximize product performance.It can solve the problem of "manufacturing decision design" in the product development process.The integrated topology optimization method and additive manufacturing technology can fully utilize the design potential and manufacturing capabilities.However,the following problems still exist in the combination of topology optimization and additive manufacturing: 1)In the process of additive manufacturing,heterogeneity and uncertainty of the structure surface layer may occur,affecting the structural performance;2)Topology optimization results have complex geometric configurations,the complexity of converting the design results to identifiable parameterization model of additive manufacture is high.Therefore,in response to the above issues,a topology optimization method and a robust topology optimization method considering surface layer heterogeneity,and a mixed topology optimization method capable of achieving geometric identification were established.Specific research content and results include:(1)A mixed topology optimization method based on SIMP-MMC framework.The combination of topology optimization methods and additive manufacturing techniques require topology optimization results to achieve the control of geometric features,and establish a parameterized model for additive manufacturing.This paper proposes a mixed topology optimization method based on the SIMP-MMC framework.This method combines the ability of finding optimal configuration of SIMP method and explicit geometry description of MMC method.It can realize the topology/shape/size intergration design.The identifiable parametric model of the additive manufacturing is also established.The main ideas are: 1)Basically looking for a topology optimization configuration based on the SIMP method;2)Identifying the geometric features of the SIMP method optimization results based on image recognition technology,and determining the number and layout of components;3)Based on the component geometry information of the previous step,the MMC method is used to optimize the boundary shape;4)The CAD model was built based on the optimized configuration of the MMC and finally printed out using additive manufacturing technology.(2)Topology optimization method of additive manufacture structures with surface layer heterogeneity considered.The surface layer heterogeneity that occurs in the additive manufacture is equivalent to a coated structure characterized by a base structure made of one material and a surface layer structure made of a different material.And a topology optimization method with surface layer heterogeneity considered is established.The main idea is to identify the surface layer of the structure based on the spatial gradient of the design field.The two-step filter method is used to separate the base structure and the surface layer.And the heterogeneity material is imposed in the surface layer.The influence of surface layer heterogeneity on the structural configuration was verified in the static mechanics with the minimum compliance.In the dynamics,taking the maximum fundamental frequency as the optimization goal,the KS function is used to fit the objective function and stiffness correction to reduce the repeated oscillation of the objective function.Using equality constraint to avoid the optimization result as the lower limit of the volume.The effect of surface layer heterogeneity on the structural configuration in the dynamic problem was verified through numerical examples.(3)Robust topology optimization of additive manufacturing structures with surface layer heterogeneity considered.Taking into account the geometric uncertainty of additive manufacture,the thickness of the heterogeneous surface layer is regarded as a random variable.Assuming that the random variable is small,the perturbation finite element method is used to evaluate the influence of random variables on the system response.Taking the weighted sum of expected value and standard deviation of structural compliance as the optimization goal,a robust topological optimization model considering the minimum objective function is established.Through the numerical examples,the robust topology optimization results under geometric uncertainty are given.Compared with the deterministic topology optimization results,the topology optimization method considering the robustness can improve the robustness of the structure.