A model for micro-slip between flat surfaces based on deformation of ellipsoidal elastic asperities—parametric study and experimental investigation

Micro-slip is a phenomenon that occurs between contacting surfaces when a frictional load, less than that necessary to produce macro-slip, is applied to the contacting surfaces. A model is evaluated for micro-slip between a flat smooth surface and a flat rough surface. The rough surface is covered with uniformly distributed ellipsoidal elastic asperities. The results from simulations of the model show that anisotropy, material combination and number of contacts of the contacting surfaces influence the tangential stiffness at zero displacement, the length of the micro-slip zone and the energy dissipated in the contact. An experimental investigation verifies the results computed by the model.     

基于谐波平衡-时频转换法的摩擦振子稳态响应分析

在振动环境中,连接结构的接合面上存在复杂的摩擦接触行为。当受到不同幅值的切向激励时,界面可能出现微滑和宏滑两种不同的摩擦行为。准确高效地求解同时考虑微滑和宏滑的摩擦振子稳态响应对连接结构设计与优化具有重要的参考意义。采用连续弹簧滑块模型(Iwan模型)描述接合面上的跨尺度摩擦行为,通过多谐波平衡和时频转换组合方法求解了单自由度和多自由度摩擦振子稳态响应。结果表明该方法具有很高的精度,并且计算效率远高于传统数值积分方法;选取的谐波截断阶次越高,对摩擦恢复力的求解越精确;频响分析表明摩擦非线性使振子幅频响应表现出了刚度软化、谐波共振等非线性现象。     

基于微滑移模型的B-G型叶片干摩擦缘板阻尼器减振特性研究

在干摩擦接触面间引入弹性剪切层来模拟干摩擦接触,考虑摩擦接触界面在振动过程中可能经历完全粘滞、局部滑移、完全滑移三个阶段,提出一种改良的微滑移摩擦阻尼模型。在该阻尼模型基础上对摩擦力-位移迟滞曲线进行了仿真,得到了符合工程实际的迟滞曲线;分析了不同外力下接触面上的摩擦分布,揭示了微滑移模型的本质;利用一次谐波平衡与等效线性化相结合,研究多种参数对阻尼器等效刚度和等效阻尼及减振特性的影响,得到的减振规律为工程中该类阻尼器设计提供了指导。     

Micro-slip test equipment for point contacts

Micro-slip can be characterised as local slip in a contact. Test equipment has been developed to study the phenomenon in point contacts. Although the equipment is designed for any point contact, the surface configuration presented here is a sphere against a flat. With the equipment, it is possible to measure accurately forces and displacements in both the normal and the tangential direction of the contact. Three-dimensional surface topography measurements of the contact surfaces can also be made before and after each test. A series of experiments has been carried out in which normal load, surface roughness, material combination, and lubrication were varied. The general experience gathered from the tests was that the equipment is accurate enough for very small contacts and is easy to use. The test results presented in this paper show tangential and normal displacement and tangential load for contacts subjected to small macro displacements, both undirectional and oscillating. The degree of plastic deformation in a contact is also shown for some tests.     

Micro-mechanism of initiation of sliding

In order to understand the effects of contact shape and sliding direction on tangential coefficient a VTR (Video Tape Recorder) computer system has been developed to visualise the micro-slip distribution at the contact interface, during the process of micro displacement, before macro sliding. It is shown that micro-slip distribution is strongly affected by the shape of the contact area and the sliding direction, which gives a good explanation of the observed relationships between tangential coefficient (defined as tangential force divided by normal load) and tangential displacement. It is suggested, as a result, that the VTR-computer system developed in this study allows useful observation and understanding of the micro-mechanism of initiation of macro sliding.     

单晶γ-TiAl合金微观滑移机制的研究

针对单晶γ-TiAl合金微观滑移机制方面研究的不足,建立了单晶γ-TiAl合金单轴拉伸时晶体滑移几何模型,根据几何模型中各夹角之间的几何关系和由Weiss晶带法则给出的滑移方向,计算出了单滑移系中各个滑移方向上的Schmid因子;通过对比计算结果发现在设定条件下晶体更易产生滑移的方向为(001)[01-1]和(11-1)[110];在由主滑移系和交滑移系组成的双滑移系同时开动时,计算出了临界外加拉伸应变为0.633;通过数值模拟验证了所给出的单晶γ-TiAl合金单轴拉伸时的微观滑移机制的正确性。     

基于振动控制的后视镜球铰摩擦能耗机理研究

建立了一种基于微动滑移摩擦理论的后视镜球铰能量耗散模型,利用刚性壁面与弹性体之间的微动滑移接触来模拟真实情况,采用指数定律给出了压力分布,推导出了球铰微动滑移干摩擦产生的能量耗散方程,并获得了正压力和滑移面积对能量耗散的影响关系曲线.最后将该模型应用于某商用车后视镜怠速振动的控制,并进行了试验与仿真计算,结果表明,所建...     

考虑法向载荷变化的Iwan模型及其特性分析

为了完整、准确地复现摩擦接触界面间的力学行为和描述其能量耗散特性,提出了一种考虑法向载荷变化的Iwan模型.在连接界面的法向上,该模型采用一个非线性弹簧来描述界面法向载荷变化和间歇性分离的行为,在其切向上则采用原始Iwan模型来描述界面间的微滑和宏滑行为;推导了切法向耦合作用下模型的恢复力和位移关系的表达式,给出了模型运动状态转换点的判据;并以简化的摩擦阻尼器模型为对象,求解了振动系统在简谐激励作用下的动力学响应,讨论了不同激励参数对系统动力学特性的影响.分析表明,当法向载荷为常值时,该模型退化为Iwan模型,从而验证了模型的准确性;该模型考虑了切向微滑行为和法向载荷变化的动态耦合,相比于不考虑法向载荷变化的模型能够更加完善、准确地模拟接触界面间的力学行为及其对系统振动响应预测的影响;连接界面的法向分离不仅会减弱系统的阻尼性能,使得系统动响应很高,而且会增强系统响应的非线性程度,在实际工程应用中应尽量避免.     

Tribology of the belt-driven data tape cartridge

The belt-driven data tape cartridge uses an elastic drive-belt to control magnetic tape tension by driving both tape supply and take-up reels. This design enables the use of a simple, compact and inexpensive cartridge drive mechanism. However, there were many tribological issues that had to be solved before this product reached its current widespread acceptance in the data storage market. This paper will address the associated friction and wear control issues. The main focus will be on polymer tribology and how attention to the micro-tribological details of each interface has been linked with improved data storage reliability and performance.