【摘要】：隨著裝備制造技術的蓬勃發(fā)展,以數(shù)字化和精密化為特征的先進制造技術也不斷向著高效率和高精度、集成化與復合化的方向發(fā)展。先進制造技術的核心競爭力依賴于數(shù)控機床的技術水平。在眾多高檔數(shù)控機床的研究領域中,銑車復合加工中心則憑借著其“以銑代車”的加工特點,通過車削主軸與動力刀架的銑刀主軸合運動,在一次裝夾的條件下可以完成全部的加工工序,進而實現(xiàn)其高速復合加工的目的。銑車復合加工中心立柱作為整個結構系統(tǒng)的承載基體,它的剛度及固有頻率性能對于零件加工精度、表面質量及加工過程的噪聲、振動都有較大影響。本文借助計算機建模與有限元仿真技術,以進一步提高立柱結構綜合力學性能為目的,探索出一種基于拓撲優(yōu)化技術與仿生設計原理為一體的機床支承件設計方法。在研究的過程中,依次從分析立柱承受的工作載荷、立柱結構的靜動態(tài)性能、多目標結構拓撲優(yōu)化、內部結構仿生設計等四個方面進行深入研究,為機床的大件設計提供新的思路。本文的主要研究內容如下:(1)依據復合加工中心實際工作情況,以銑削HT300材料為前提,首先具體分析和計算復合加工中心在最大工作載荷位置和典型加工位置工況下立柱的受力狀況。然后建立立柱有限元模型,以最大工作載荷位置工況為條件進行立柱結構的靜力學與動態(tài)性能分析。從仿真分析的結果中發(fā)現(xiàn),立柱的最大變形發(fā)生在左側立柱頂部位置,總體最大變形量為0.248 mm,主要以Y方向變形為最大變形方向;得到了立柱前六階固有頻率及其對應振型,并根據諧響應分析結果得到激振頻率為80Hz時在立柱上會發(fā)生較為明顯的位移。(2)基于拓撲優(yōu)化中的變密度法,首先總結并建立了立柱結構多目標拓撲優(yōu)化完整的數(shù)學模型。然后利用Hyper Work軟件,建立立柱拓撲優(yōu)化初始迭代有限元模型,通過對非設計域施加兩種靜態(tài)工況子目標和對全局設置一種動態(tài)低階頻率響應約束,求解并獲得多目標拓撲優(yōu)化立柱結構的載荷傳遞路徑。最后根據拓撲優(yōu)化結果,提出了在保持立柱原有外形不變的情況下對立柱內部進行結構設計的優(yōu)化建議,同時為下一步運用結構仿生設計方法對內部筋板隔板進行設計與布局奠定基礎。(3)根據優(yōu)化建議確定的設計方向,從立柱的薄壁多腔結構特性與空莖植物結構相似性出發(fā),分析芭蕉葉柄結構的力學與構型特性,并對其結構中起主要作用的六邊形網格單元進行計算。然后提取三種芭蕉葉柄結構的衍生結構,以此為依據設計出三種仿生型隔板方案,并進一步結合拓撲優(yōu)化建議,采用太陽筋板和井字型筋板分密度和梯度重新對立柱內部結構進行設計,建立了三種仿生型立柱三維模型。(4)通過對三種仿生型立柱結構進行靜力學和模態(tài)分析的結果中發(fā)現(xiàn),在相同載荷與約束條件下,A、B、C三種仿生設計方案的立柱的比剛度效能較原型設計分別提高了85.94%、82.53%和89.60%,綜合力學性能提升十分明顯。其中以仿生型C立柱的靜動態(tài)性能最為優(yōu)異,與原型設計相比較,其最大變形總量減小了48.35%,誤差敏感方向Y方向上變形減小了70.41%,立柱前六階模態(tài)的固有頻率平均提升17.50%左右,且在前六階模態(tài)下的最大變形也有顯著減小。因此,仿生設計后的立柱在進一步高效利用材料的同時,其靜動態(tài)特性得到顯著的提升,實現(xiàn)了以高比剛度為目的的立柱結構優(yōu)化設計。
[Abstract]:With the vigorous development of equipment manufacturing technology, the advanced manufacturing technology characterized by digitalization and precision is also developing towards high efficiency, high precision, integration and compounding. The core competitiveness of advanced manufacturing technology depends on the technical level of NC machine tools. By virtue of the machining characteristics of "replacing turning with milling", the machining center can complete all the machining procedures under the condition of one-time clamping by turning the spindle and the milling cutter spindle of the power tool holder, and then realize the purpose of high-speed composite machining. The stiffness and natural frequency performance have great influence on the machining accuracy, surface quality, noise and vibration of the parts in the machining process. In order to further improve the comprehensive mechanical properties of the column structure, this paper explores a mechanism based on topological optimization technology and bionic design principle. In the course of the research, the design method of the supporting parts of the machine tool is studied from four aspects: the analysis of the working load of the column, the static and dynamic performance of the column structure, the multi-objective topology optimization, and the bionic design of the internal structure. On the premise of milling HT300 material, the actual working condition of the machining center is analyzed and calculated firstly. Then the finite element model of the column is established to carry out the static and dynamic analysis of the column structure under the condition of the maximum working load position and the typical working position. The results show that the maximum deformation of the column occurs at the top of the left column, and the total maximum deformation is 0.248 mm, mainly in the direction of Y. The first six natural frequencies and their corresponding modes of vibration of the column are obtained, and the excitation frequency is 80 Hz according to the harmonic response analysis results. (2) Based on the variable density method in topology optimization, a complete mathematical model for multi-objective topology optimization of column structure is summarized and established. Then, the initial iteration finite element model of column topology optimization is established by using Hyper Work software, and two static sub-objectives and sub-objectives are imposed on the non-design domain. A dynamic low-order frequency response constraint is set up globally to solve and obtain the load transfer path of multi-objective topological optimization column structure. Finally, according to the topological optimization results, the optimization suggestions of structural design for the column interior are put forward under the condition of keeping the original shape of the column unchanged, and the structural bionic design is used for the next step. (3) According to the design direction determined by the optimization proposals, the mechanical and structural characteristics of the petiole structure of banana were analyzed from the characteristics of thin-walled multi-cavity structure and the similarity of the structure of the hollow plant, and the hexagonal mesh element which played a major role in the structure was calculated. After extracting the derivative structures of three kinds of banana petiole structures, three bionic separator schemes were designed based on these schemes, and further combined with topological optimization suggestions, the inner structure of the column was redesigned by using the partial density and gradient of solar and well-shaped rib plates, and three bionic three-dimensional models of the column were established. The results of static and modal analysis show that under the same load and restraint conditions, the specific stiffness efficiency of A, B and C columns with three bionic design schemes is 85.94%, 82.53% and 89.60% higher than that of the prototype design, respectively. The comprehensive mechanical properties are greatly improved. Among them, the static and dynamic performance of bionic C columns is the best. Compared with the prototype design, the maximum deformation is reduced by 48.35%, the deformation in the Y direction is reduced by 70.41%, the natural frequency of the first six modes is increased by 17.50%, and the maximum deformation in the first six modes is also significantly reduced. The static and dynamic characteristics of the column structure are significantly improved and the optimum design of the column structure for the purpose of high specific stiffness is realized.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG547

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