Contact Stiffness Idetifiction Method for Joint Surface and the Effect of Contact Stiffness on the Dynamic Response of the Cable Bracket

The cable bracket is one of the crucial components of high-speed Electric Multiple Units(EMUs), which is fixed to the axle box by bolts to support the cable. As an important parameter of the joint surface, contact stiffness significantly affects the dynamic response and service life of the cable bracket. However, it is difficult to directly measure the contact stiffness of the joint surface. As a result, an identification method is proposed in this investigation to identify the contact stiffness. A finite element model incorporating both normal and tangential stiffness parameters is developed. According to the finite element model and modal testing results, an improved particle swarm optimization algorithm is employed to identify the contact stiffness of the joint surface. The effect of the contact stiffness on the vibrations of the cable bracket is investigated. The findings indicate that pre-tightening torque significantly influences the contact stiffness of the cable bracket. The contact stiffness has a great effect on the vibrations of the cable bracket. Optimal contact stiffness notably reduces vibrations of the cable bracket, thereby extending its service life.     

螺旋弹簧横向静刚度计算及动刚度频变分析

为探究等截面圆柱形螺旋压缩弹簧横向静刚度及动刚度特性,建立弹簧离散模型,进行有限元分析.静载下,修正Krettek刚度公式,使其兼顾弹簧受载端的垂向压缩量和横向位移量等因素对横向静刚度的影响.动载下,进行频变分析,绘制横向动刚度随激励频率变化曲线.结果表明:横向动刚度随激励频率的提高呈波动上升的趋势;可以通过改变横向激...     

弹性浮动研磨接触面接触刚度接触阻尼的算法

在机械结合面中存在的接触刚度和接触阻尼影响加工过程中机械表面的质量。提出了弹性浮动研磨过程中的接触刚度和基础阻尼的计算方法,采用实验的方法测出振幅与时间的数据,再利用曲线拟合的方法拟合出接触刚度和接触阻尼值。     

线外啮合齿轮传动啮合刚度计算

对变形和误差引起的线外啮合进行了研究与分析，提出了一种基于线外啮合的齿轮传动刚度计算方法。     

Contact Stiffness of Machine Components and the Influence of the Microgeometry of the Contact Surfaces on It

The use of characteristics of the contact stiffness in the scientific literature to describe a discrete contact between machine components under normal and tangential loading has been analyzed. The application of a model of the discrete contact of rough surfaces, as well as the influence of the parameters of the contact surface microgeometry on the contact stiffness under normal and tangential loadings and shear has been studied.     

Energy, Adhesion, and the Elastic Foundation

A theory for elastic contact adhesion between a rigid sphere and an elastic foundation is developed. The theory derives relationships between the contact deformation and the externally applied force. The derivation is based on elastic contact between a sphere and a thin linear-elastic foundation in which the strain energies are balanced by the work of indentation and the change in surface energy. Contacting regimes where there is either compressive strain energy or only tensile strain energy (pull-off regime) are both treated. The model is non-dimensionalized and an order of magnitude analysis is performed in order to develop simplified closed form solutions; the simplified model is then evaluated and compared to the full solution. This theory finds that the adhesion force is significantly larger for an elastic foundation in which the surface elements act independently as compared to more traditional solutions for elastic solids. The theory gives an adhesion force of $ F_{\text{adh}} \cong 7\pi R\Updelta \gamma . $      

基于分形几何与接触力学理论的结合面法向接触刚度计算模型

基于分形几何理论和接触力学理论,用分形理论表征粗糙表面微凸体参数,考虑微凸体由弹性变形向弹塑性变形以至最终向完全塑性变形转化的过程,建立各变形阶段微凸体的接触刚度模型。在此基础上,提出机械结合面法向接触刚度计算模型,该模型揭示了在不同的塑性指数下,结合面法向接触载荷与法向接触刚度之间的关系。结果表明,在塑性指数较小时,微凸体的变形以弹性为主,法向接触载荷与接触刚度之间表现为近似线性关系;随着塑性指数的增加,微凸体变形主要以塑性为主,法向接触载荷与接触刚度之间表现为较强非线性关系。对已有的铣削加工和磨削加工情况下的结合面法向接触刚度试验结果,利用该模型进行数值计算、仿真和分析。结果表明:提出的模型更与试验曲线吻合。     

弹性接触问题的计算机辅助分析

论述了两个弹性体之间点或线接触问题的理论及其计算机算法关键 ,表明完全可以采用计算机辅助分析手段直接进行求解。通过对各种主要弹性趋近量算式来源的阐述和相应计算结果的对比分析 ,得出了几条相关结论。这些结论可供相关工程研究人员尤其是轴承工作者参考     

四点接触球轴承轴向刚度的测量

阐述了四点接触球轴承的工作机理,提出利用数控机床的微进给控制加载的方法,对四点接触球轴承轴向刚度进行精密测量,分析了影响测量精度的主要原因,介绍了测试过程中的主要技术措施。通过实测得到某型号四点接触球轴承的轴向刚度曲线,为其实际应用提供科学依据,该方法对其他复杂零件的轴向刚度测量,具有工程参考价值。     

超声波测量接触刚度的研究进展

介绍了超声波测量接触刚度的基本理论、实验方法和影响因素,对超声波测量接触刚度的研究历史和现状进行了分析和总结。超声波的波长远大于微凸体接触尺寸,接触表面的反射系数和入射系数是接触刚度的函数,根据实验获得的入射系数或者反射系数可以计算出接触刚度。超声波的频率、接触压力和材料的物理性质对接触刚度的测量有一定影响,接触压力较大时,纵波的反射系数和透射系数对载荷的变化不敏感,在这种情况下用横波检测比较好。利用超声波测量的接触刚度与理论计算出的刚度具有较好的一致性,表明超声波方法可以用于测量接触刚度并且具有一定可靠性。指出了超声波测量接触刚度研究中存在的问题和困难,展望了该技术在机械接触刚度测量方面的发展趋势。     

角接触球轴承静态刚度试验

角接触球轴承在径向、轴向以及力矩方向联合载荷作用下,内外圈将产生径向、轴向相对位移及相对倾角。这种弹性相对位移量的大小关系到轴承的使用性能。为了得到角接触球轴承静刚度,提出了角接触球轴承静刚度的测试方法。设计了测量装置,获取施加不同载荷作用下角接触球轴承的静刚度。分析结果表明:随着轴向载荷或径向载荷的增大,轴向变形或径向变形基本上呈现线性增长,轴向刚度和径向刚度呈现非线性增长;随着轴承尺寸的增大,轴承的静态刚度也增大。     

弹性环组件刚度特性仿真与试验

对涡轮机转子系统弹性支承中弹性环组件的刚度特性进行仿真与试验研究.在研究中,利用有限元方法对弹性环组件进行接触分析,换算得到弹性环组件的刚度.根据实际受力特点,设计测量弹性环组件刚度的试验装置,并进行试验.试验结果表明,当对弹性环反复加载卸载时,会出现明显的迟滞回线现象.随着径向间隙的增大,迟滞回线现象逐渐减弱,弹性环...     

准零刚度隔振器及其弹性特性设计

结合电子行业军用标准《准零刚度隔振器设计与应用技术导则》的编制工作，介绍了准零刚度隔振器的定义、分类及其设计方法，并有线性准零刚度隔振器及非线性准零刚度隔振器的设计示例。     

Intermolecular Forces, Adhesion, and the Elastic Foundation

A model for the elastic contact between a rigid sphere and an ideal elastic foundation with adhesion has been developed. The model was derived by integrating the full Lennard-Jones potential to arrive at a closed-form equilibrium condition that balances surface energy with strain energy. It was found that the separation height is not a function of the penetration. Using this energy criterion for separation of contact in an elastic foundation, a model for the force displacement relationship was then developed. In this derivation there exists a tensile zone of deformation along the perimeter of the contact. The model also reveals a number of unique aspects of the adhesive contact, including: the maximum adhesion occurs when the apex of the sphere is tangent to the plane of the undeformed surface, the maximum adhesion force $ F_{\text{adh}} = - 2\pi R\Updelta \gamma $ , and the contact area is linearly dependent on penetration. The ability to fit high fidelity indentation data from finite-element analysis and molecular dynamics simulation for thin films was demonstrated. Additionally, experiments were performed on thin films (~40 μm) of PDMS using a custom-built microtribometer with in situ optical interferometry that enabled simultaneous measurements of contact area, penetration depths, externally applied force, and the detailed measurements of the free-surface deformations, which include the predicted tensile zone along the perimeter of contact.     

一种考虑润滑效应的角接触球轴承接触刚度计算方法

建立了润滑工况下的高速角接触球轴承动力学模型,在滚珠与内/外圈的接触变形和接触刚度计算中,考虑高速转动中润滑油卷吸作用和挤压效应的影响,通过接触角和接触刚度的耦合迭代,得到考虑润滑效应的高速角接触球轴承轴向及径向刚度计算方法.结果表明,考虑润滑效应后,滚珠与内/外圈的接触角减小,轴承轴向/径向刚度增大;轴向载荷增加使轴...     

On the Modeling of Elastic Contact between Rough Surfaces

The contact force and the real contact area between rough surfaces are important in the prediction of friction, wear, adhesion, and electrical and thermal contact resistance. Over the last four decades various mathematical models have been developed. Built on very different assumptions and underlying mathematical frameworks, model agreement or effectiveness has never been thoroughly investigated. This work uses several measured profiles of real surfaces having vastly different roughness characteristics to predict contact areas and forces from various elastic contact models and contrast them to a deterministic fast Fourier transform (FFT)-based contact model. The latter is considered “exact” because surfaces are analyzed as they are measured, accounting for all peaks and valleys without compromise. Though measurement uncertainties and resolution issues prevail, the same surfaces are kept constant (i.e., are identical) for all models considered. Nonetheless, the effect of the data resolution of measured surface profiles will be investigated as well. An exact closed-form solution is offered for the widely used Greenwood and Williamson (GW) model (Greenwood and Williamson, Proceedings of the Royal Society of London A, vol. 295, pp. 300–319), along with an alternative definition of the plasticity index that is based on a multiscale approach. The results reveal that several of the theoretical models show good quantitative and qualitative agreement among themselves, but though most models produce a nominally linear relationship between the real contact area and load, the deterministic model suggests otherwise in some cases. Regardless, all of the said models reduce the complicated surface profiles to only a few key parameters and it is therefore unrealistic to expect them to make precise predictions for all cases.     

提高大型机床床身、垫铁、基础系统接触刚度的措施

大型机床安装调平中 ,床身、垫铁、基础的表面质量及接触精度对其接触刚度有着较大的影响 ,总结了提高机床接触刚度的措施及其灌浆要点 ,该措施可增强机床精度的稳定性。     

鱼雷壳体与试验台架的接触刚度分析

在试验台架上对鱼雷进行冷、热车试验时,试验台架与壳体之间的接触刚度对试验结果有很大影响,同时也是考察台架是否压坏鱼雷试件的一个重要因素,本文中使用ABAQUS软件对鱼雷壳体与台架的接触刚度进行有限元建模计算,并与理论计算结果进行对比。对结果中的接触应力集中及接触应力曲线不连续等现象进行了分析,讨论了壳体弹性模量对接触应力曲线不连续性的影响。结果表明:在壳体上存在应力集中区域的附近同时存在着接触应力曲线沿环向的分布不连续现象,进一步的研究表明接触应力曲线的不连续程度与壳体弹性模量有关,弹性模量越大,该曲线的不连续程度越大。     

基于弹性接触的销轴结构应力分析

为了更加准确地对销轴结构进行应力分析,提出将刚度矩阵和赫兹接触理论相结合的弹性接触应力求解方式。考虑销轴结构在工作状态下具有接触突变的特性,根据接触刚度矩阵,推导出接触状态判别式,辅以基于弹性接触的赫兹接触理论,建立了销轴结构应力方程。以某销轴结构为例,应用弹性接触应力方程计算销轴结构的接触应力,证明了提出求解方式的正确性。     

机器人驱动机构中弹性元件功能分析及刚度设计

为了研究弹性元件在仿人机器人腿部弹性驱动机构中的具体功能,并选择合适刚度的弹性元件,以典型的弹性驱动器为基础,建立了弹性驱动器的位置源驱动模型以及仿人机器人小腿弹性驱动机构模型。对驱动机构重要参数进行优化,确定最优参数值,在给定转角范围内,通过仿真计算分别得到转角和驱动力与驱动位移关系图。对比不同弹簧刚度下的关系曲线,利用MATLAB函数确定最优刚度值,得出在合适的弹簧刚度下,弹性元件具有增强机器人小腿驱动稳定性和精确性的功能的结论。