【作者】 周杰；

【导师】 高宏力；

【作者基本信息】 西南交通大学 ， 机械工程（专业学位）， 2018， 硕士

【摘要】 当机床处于高速加工状态时,其进给系统的不可控振动对工件加工质量影响巨大,为提高机床结构的稳定性、减小振动,必须对其开展动力学研究。在常用的有限元仿真中,结构的可动结合部通常被简单的定义为绑定接触,忽略了可动结合部间复杂的接触情况。特别是对具有大量可动结合部的复杂装配体进行研究时,有限元计算存在很大的误差。本文以具有典型进给系统的丝杠加速寿命试验台为研究对象,从试验台静止状态和工作状态两种情况出发,采用动力学建模、有限元仿真和模态实验三者相结合的方法,对丝杠加速寿命试验台的结构动力学及振动特性进行了全面的研究。具体内容如下:第一,简述了丝杠加速寿命试验台的机电系统构成、结构特点与安装方式,为接下来的计算、仿真和实验工作做准备。第二,利用赫兹接触理论,根据试验台进给系统中可动结合部的接触特性,自编程计算出了其丝杠、轴承和导轨的接触刚度。将接触刚度赋值到有限元软件的弹簧单元中后,在有限元软件中建立起了基于结合部刚度特性的系统结构动力学模型。第三,对试验台进行了有限元模态分析,在有限元分析结果的基础上,利用搭建的模态测试系统对试验台进行了锤击模态实验。通过有限元振型结果确定了合适的拾振点;通过对比多次试验的模态振型结果,确定了能完整展示模态振型的测点个数;通过更换锤头的材质进行试敲击,选择了能实现结构充分激励的锤头;完成实验模态分析,获得了系统的模态参数。最终将三种方法的计算结果进行对比,验证了本文提出模型的准确性。第四,针对此类设备长期处于运行工况下的特点,利用工作模态分析方法对试验台进行了振动特性分析。得到了不同工况下系统的固有频率,分析了转速与轴向负载力对振动特性与固有频率的影响。本论文从丝杠加速寿命试验台静止状态和工作状态两种角度入手对其开展动力学研究。为机床等复杂装配体的动态特性研究提供了合理的动力学模型与全面的研究方法,为机床模态分析、结构优化与故障诊断提供了依据。更多还原

【Abstract】 When the machine tool is in a high speed machining state,the uncontrollable vibration of the feed system has a great influence on the machining quality of work-piece.In order to improve the stability of machine tool structure and reduce vibration,dynamic research is necessary.In the commonly used finite element simulation method,the rolling joints of the structure are usually simply defined as bonding contact,and the complex contact form between the rolling joints are ignored.In particular,the finite element calculation may have a great error in the study of the dynamic characteristics of a complex assembly,who has a large number of rolling joints.In this paper,the ball screw test bench with typical screw feed system is chosen as the object of the research.Considering the static state and the operation state,the comprehensive research of the dynamic and vibration characteristics of the ball screw test bench are finished by using dynamics modeling,finite element simulation and modal experiment.The details are shown as follows:Firstly,the composition of the electromechanical system,structure characteristics and installation method of the ball screw test bench are briefly described to prepare the following calculation,simulation and experiment.Secondly,The Hertz contact theory are used to calculate the contact stiffness of the ball screw,bearing and liner guide according to the contact characteristics of the rolling joints in the test bench’s feed system.After the contact stiffness is assigned to the spring element in the finite element software,the modified dynamic model of the system is set up by finite element software.Thirdly,the finite element modal analysis of the test bench is carried out.Based on the results of finite element analysis,the test bench was analyzed by using impact hammer modal test.Then the suitable vibration pick-up points are determined by the finite element mode.And the number of modal measurement points that can fully display the mode of vibration is determined by comparing the mode shapes of multiple tests.Furthermore,base on change the material of the hammer head and test,the hammer head which can achieve structure’s fully excitation is determined.At this point,the experimental modal analysis is completed and the exact modal parameters of the system are obtained.At last,the accuracy of this model is verified by comparing the results of three methods.Fourth,aiming at the characteristics that this kind of equipments always do continuous work for a long term,the operation mode analysis of the test bench is carried out.The natural frequency of the system under different working conditions is obtained,and the influence trends of rotational speed and axial load on the vibration and natural frequency is obtained by analysing the experimental results.In this paper,the dynamic characteristics of the ball screw test bench are studied from two aspects: the static state and the working state.It provides a reasonable dynamic model and a comprehensive research method for the dynamic characteristics of the complex assemble structures like machine tools,and also provides the basis for modal analysis,structure optimization and fault diagnosis of machine tools.更多还原