铣车复合加工中心立柱结构拓扑优化及仿生设计研究

发布时间：2018-08-28 14:54

【摘要】：随着装备制造技术的蓬勃发展,以数字化和精密化为特征的先进制造技术也不断向着高效率和高精度、集成化与复合化的方向发展。先进制造技术的核心竞争力依赖于数控机床的技术水平。在众多高档数控机床的研究领域中,铣车复合加工中心则凭借着其“以铣代车”的加工特点,通过车削主轴与动力刀架的铣刀主轴合运动,在一次装夹的条件下可以完成全部的加工工序,进而实现其高速复合加工的目的。铣车复合加工中心立柱作为整个结构系统的承载基体,它的刚度及固有频率性能对于零件加工精度、表面质量及加工过程的噪声、振动都有较大影响。本文借助计算机建模与有限元仿真技术,以进一步提高立柱结构综合力学性能为目的,探索出一种基于拓扑优化技术与仿生设计原理为一体的机床支承件设计方法。在研究的过程中,依次从分析立柱承受的工作载荷、立柱结构的静动态性能、多目标结构拓扑优化、内部结构仿生设计等四个方面进行深入研究,为机床的大件设计提供新的思路。本文的主要研究内容如下:(1)依据复合加工中心实际工作情况,以铣削HT300材料为前提,首先具体分析和计算复合加工中心在最大工作载荷位置和典型加工位置工况下立柱的受力状况。然后建立立柱有限元模型,以最大工作载荷位置工况为条件进行立柱结构的静力学与动态性能分析。从仿真分析的结果中发现,立柱的最大变形发生在左侧立柱顶部位置,总体最大变形量为0.248 mm,主要以Y方向变形为最大变形方向;得到了立柱前六阶固有频率及其对应振型,并根据谐响应分析结果得到激振频率为80Hz时在立柱上会发生较为明显的位移。(2)基于拓扑优化中的变密度法,首先总结并建立了立柱结构多目标拓扑优化完整的数学模型。然后利用Hyper Work软件,建立立柱拓扑优化初始迭代有限元模型,通过对非设计域施加两种静态工况子目标和对全局设置一种动态低阶频率响应约束,求解并获得多目标拓扑优化立柱结构的载荷传递路径。最后根据拓扑优化结果,提出了在保持立柱原有外形不变的情况下对立柱内部进行结构设计的优化建议,同时为下一步运用结构仿生设计方法对内部筋板隔板进行设计与布局奠定基础。(3)根据优化建议确定的设计方向,从立柱的薄壁多腔结构特性与空茎植物结构相似性出发,分析芭蕉叶柄结构的力学与构型特性,并对其结构中起主要作用的六边形网格单元进行计算。然后提取三种芭蕉叶柄结构的衍生结构,以此为依据设计出三种仿生型隔板方案,并进一步结合拓扑优化建议,采用太阳筋板和井字型筋板分密度和梯度重新对立柱内部结构进行设计,建立了三种仿生型立柱三维模型。(4)通过对三种仿生型立柱结构进行静力学和模态分析的结果中发现,在相同载荷与约束条件下,A、B、C三种仿生设计方案的立柱的比刚度效能较原型设计分别提高了85.94%、82.53%和89.60%,综合力学性能提升十分明显。其中以仿生型C立柱的静动态性能最为优异,与原型设计相比较,其最大变形总量减小了48.35%,误差敏感方向Y方向上变形减小了70.41%,立柱前六阶模态的固有频率平均提升17.50%左右,且在前六阶模态下的最大变形也有显著减小。因此,仿生设计后的立柱在进一步高效利用材料的同时,其静动态特性得到显著的提升,实现了以高比刚度为目的的立柱结构优化设计。
[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.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG547

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