机床固定结合部动力学特性与整机动力学建模研究

发布时间：2018-07-26 13:20

【摘要】：现代高效高精度加工对机床性能要求越来越高,且有竞争力的机床生命周期不断缩短,传统的物理原型机制造、测试、修改、优化的设计方法逐渐不能满足现代机床设计需求。运用虚拟机床技术建立机床结构的数学模型,在设计阶段预测机床静动态性能,并根据预测结果修正设计方案,最终达到设计要求是实现高效高水平机床设计的一种新途径。建立能准确模拟机床结构静动态特性的数学模型是虚拟机床技术的基础,而机床结合部的建模则是机床结构建模中的难点和关键。本文以数控机床结合部为研究对象,运用有限单元法、实验模态分析法和现代优化设计方法,对机床结构动力学建模中的结合部建模、模型参数获取、影响因素分析和应用技术四个关键技术展开深入研究。主要工作有如下几点：第一,提出主轴-刀柄锥面配合固定结合部的带锥度的有限单元模型及参数识别方法。该模型用带锥度的有限单元刚度矩阵和阻尼比系数来模拟主轴-刀柄锥面配合固定结合部的动态固有特性。基于结构频响函数矩阵与动刚度矩阵互逆关系,利用模态实验法测试得到的频响函数识别带锥度的有限单元参数。通过不同数学模型计算结果与实验值的比较,验证了该有限单元模型能够准确模拟锥面配合固定结合部的动力学特性。第二,分析结构材料对机床螺栓固定结合部动力学特性的影响。分别基于Hertz接触理论和实验模态分析法,推导了不同材料配对螺栓固定结合部单元刚度矩阵与螺栓连接部件材料的等效弹性模量之间的统计模型。通过机床常见的螺栓连接部件建模应用,验证该统计模型的正确性。该正比关系定量的揭示了材料参数对螺栓固定结合部动力学特性的影响,为螺栓固定结合部单元模型的广泛应用提供了便利。第三,基于结合部精确模型的机床结构动力学建模。将螺栓固定结合部和锥面配合固定结合部的有限单元模型集成到有限元软件中,与结构组件的有限元模型、可动结合部的弹簧单元模型,合成机床整机结构动力学模型。将该方法应用于CKX5680机床、YK31320滚齿机结构和XCM1600机床整机结构动力学建模,模型计算的机床结构静、动态特性参数与实验值基本一致,说明该建模方法能够准确建立机床结构动力学模型。第四,以提高结构的动力学特性为目标,采用优化方法确定机床多单元螺栓固定结合部动力学特性影响因素。基于螺栓固定结合部动力学特性影响因素分析,确定优化设计变量为螺栓数目和公称直径。通过约束条件分析,确定螺栓数目和公称直径的可行解范围。根据许可的频率损耗因子,在可行解范围内,选取最优的螺栓数目和公称直径使结构获得更好的动力学特性。为机床多单元螺栓固定结合部结合面参数确定提供了一种有效的方法。最后,以XCM1600机床为例,分析结合部对机床结构柔度分布影响机制。建立该机床结构的内力传递路径等效弹簧模型和柔度分布表征。利用所建立的XCM1600机床整机结构有限元模型计算结果,结合机床结构在内力传递路径等效弹簧模型,分析机床结合部对整机静态柔度影响系数的影响,结果显示机床结合部对整机X、Z方向静态柔度的贡献度分别为18.1532%和27.3615%。本文围绕机床固定结合部动力学建模及应用展开研究。建立机床锥面配合固定结合部的带锥度的有限单元模型,确定螺栓固定结合部动力学特性与材料属性参数之间的统计模型。在基于刚度影响因子法的螺栓固定结合部动力学模型及与单元尺寸、预紧力及材料属性参数之间的定量关系的基础上,对机床多单元螺栓固定结合部参数进行优化设计。基于所提出的固定结合部动力学模型,并综合可动结合部经典弹簧单元模型,提出机床整机结构动力学建模思路,通过机床结构动力学建模示例验证该建模思路的有效性和正确性。并在此基础上,分析结合部对机床整机结构静态柔度分布的影响机制。
[Abstract]:Modern high efficiency and high precision machining is becoming more and more demanding for machine tool performance, and the life cycle of competitive machine tools is shortened. The traditional design method of physical prototyping, testing, modification and optimization can not meet the needs of modern machine tool design. The mathematical model of machine tool structure is established by using virtual machine tool technology, and the design stage is predicted. The static and dynamic performance of the machine tool is a new way to realize the design of high efficiency and high level machine tool. It is the foundation of the virtual machine tool technology to simulate the static and dynamic characteristics of the machine tool structure accurately, and the modeling of the machine tool junction is the difficult point in the modeling of the machine tool. And the key.
This paper, taking the joint of CNC machine tools as the research object, uses the finite element method, the experimental modal analysis method and the modern optimization design method, studies the combined part modeling, the model parameter acquisition, the influence factor analysis and the application technology of the four key technologies in the machine tool structure dynamics modeling. The main work has the following points:
First, the finite element model and parameter identification method of the spindle taper with the fixed joint are proposed. The model uses the finite element stiffness matrix and the damping ratio coefficient to simulate the dynamic inherent characteristics of the spindle - knife handle conical surface with the fixed joint, and the interaction between the structure frequency response matrix and the dynamic stiffness matrix. The frequency response function tested by the modal experiment method is used to identify the finite element parameters with taper. By comparing the calculated results with the experimental values of different mathematical models, it is proved that the finite element model can accurately simulate the dynamic characteristics of the conical surface with the fixed joint.
Second, the influence of structural material on the dynamic characteristics of the bolt fixed joint is analyzed. Based on the Hertz contact theory and the experimental modal analysis method, the statistical model of the equivalent elastic modulus of the stiffness matrix of the fixed combined part of the bolt and the material of the bolt connecting parts is derived respectively. The correctness of the model is verified by the modeling application of the connected components. The positive ratio relationship reveals the effect of the material parameters on the dynamic characteristics of the fixed joint of the bolt, which provides convenience for the wide application of the model of the bolt fixed joint unit.
Third, based on the dynamic modeling of the machine tool structure with the precise model of the combined part, the finite element model of the bolt fixed joint and the conical surface is integrated into the finite element software, the finite element model of the structural component, the spring element model of the movable part and the dynamic model of the machine tool whole machine. The application of this method is applied. The structure of the CKX5680 machine tool, the YK31320 hobbing machine structure and the whole structure dynamics of the XCM1600 machine tool are modeled. The structure of the machine tool is static, and the dynamic characteristic parameters are basically the same as the experimental values. It shows that the modeling method can establish the dynamic model of the machine tool structure accurately.
Fourth, in order to improve the dynamic characteristics of the structure, the optimization method is used to determine the influence factors of the dynamic characteristics of the fixed joint of the multi unit bolt of the machine tool. The number of bolts and the nominal diameter of the bolt are determined based on the analysis of the influence factors of the dynamic characteristics of the bolt fixed joint. The number of bolts is determined by the constraint condition analysis. According to the permitted frequency loss factor, the optimal number of bolts and nominal diameter can be selected to make the structure better dynamic characteristics in the range of the feasible solution. It provides an effective method for determining the joint surface parameters of the multi unit bolt fixed joint of the machine tool.
Finally, taking the XCM1600 machine tool as an example, the influence mechanism of the joint part on the flexibility distribution of the machine tool structure is analyzed. The equivalent spring model and the flexibility distribution of the internal force transmission path of the machine tool structure are established. The calculation results of the finite element model of the whole machine structure of the XCM1600 machine tool are used, and the equivalent spring model of the internal force transmission path is combined with the structure of the machine bed. The influence of the machine tool combination section on the static flexibility influence coefficient of the machine is analyzed. The results show that the contribution of the machine tool combination to the static flexibility of the whole machine X and Z direction is 18.1532% and 27.3615%., respectively.
In this paper, the dynamic modeling and application of the fixed joint part of the machine tool are studied. The finite element model of the taper with the conical surface of the machine tool is established, and the statistical model between the dynamic characteristics of the bolt fixed joint and the material property parameters is determined. The dynamic model of the bolt fixed joint based on the stiffness influence factor method is established. On the basis of the quantitative relation between the element size, the pretightening force and the material property parameters, the parameters of the fixed joint part of the machine tool multi unit bolt are optimized. Based on the dynamic model of the fixed joint part and the classical spring element model of the movable joint, the dynamic modeling idea of the machine tool machine is put forward. The dynamic modeling of machine tool structure validates the validity and correctness of the modeling idea, and on this basis, the influence mechanism of the joint part on the static flexibility distribution of machine tool structure is analyzed.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG659

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