Tolerance Design Of Topology-optimized Structures For Precise Manufacturing Of Stiffness Performance

Topology optimization can obtain the optimal geometric configuration of structures based on the material definition and constraints,which can realize the structural and functional integration design under the premise that the topological configuration is unknown.With the development of topology optimization,domestic and foreign scholars have designed a variety of structural and functional integrated structures for different applications,such as vibration control,multi-physics coupling,and electromagnetic wave stealth and so on.This kind of structures,for examples,flexible micro clamps,zero thermal expansion structures,negative Poisson ratio structures and functionally gradient materials,greatly improve the performance of parts in special applications.For the structure characteristics and applicable occasions of such parts,the high-precision manufacturing of geometry is not the only goal,and the performance of structures should be the most important goal to be considered about,which aims to realize the integrated manufacturing of geometry and performance.Aiming at the performance precision manufacturing of topology optimization structures,the study starts with the mechanical tolerance design in the precision manufacturing of topology structure stiffness performance,which focuses on the limitations of the traditional line profile and the tolerance analysis method to solve manufacturing errors constraint problem of topology optimization structures irregular contour.The study proposes a complete set of mechanical tolerance design methods for the performance precise manufacturing of topology structures.The main work includes the following aspects:1.The CAD model reconstruction issue of topology optimization results in terms of structural response accuracy is studied.Based on the performance sensitivity analysis of boundary discrete points,the parametric model of topology optimization results is created through boundary parameterization,contour segmentation,boundary reconstruction and other processes.The experiment results show that the reconstruction method can balance the geometric similarity and the performance of topology optimization results and improve the manufacturability of topology optimization structures,which greatly reduces the difficulty of tolerance design.2.An overall tolerance design method based on the line profile is proposed.The finite element analysis model of the line profile error is established.The mathematical relationship model between line profile errors and the topology optimization structure performance is created by finite element analysis.Then the overall tolerance allocation method is used to calculate the corresponding performance tolerance value.Tolerance design examples prove that the method can achieve performance-oriented design under the condition of strong manufacturing capability and acceptable manufacturing cost.However,its design freedom is low.If the cost optimization is required,only the product quality must be reduced.3.A performance-oriented segmentation tolerance design method with the improved line profile model and the non-uniform and asymmetric tolerance zone driven by performance metrics is proposed.In the segment tolerance design,the concept of the compensating contour is proposed.And the internal offset effect of the structure is used to relax the tolerance requirement of other remaining machining contours,which greatly reduces the difficulty of topology optimization structures manufacturing.Tolerance design examples prove that the method can effectively reduce costs and improve the tolerance design freedom in performance-oriented manufacturing,which can achieve the multi-objective optimization of tolerance design.4.Compared with the overall tolerance design method of the line profile model and the segment tolerance design method of the improved line profile,the selection principle of line profile models,tolerance analysis methods and tolerance allocation methods for different occasions is proposed.In addition,a free curve verification model with manufacturing error is proposed.The Monte Carlo method is used to verify tolerance design results.The simulation results show that all the tolerance design results are qualified.