摩擦离合器黏滑振动特性的显式动力学分析

针对摩擦离合器在接合过程中出现的黏滑振动问题,建立了某车型离合器三维有限元模型,通过采用有限元软件ABAQUS内嵌的显式动力学分析算法,对离合器系统在接合过程中产生的黏滑振动特性进行研究,通过改变法向载荷和摩擦片厚度,探讨了两者对离合器系统黏滑振动行为的影响.研究结果表明,利用ABAQUS显式动力学分析能有效地模拟出离合器接合过程中产生的黏滑振动现象.黏滑振动发生过程中,系统位移信号呈现出明显的锯齿状波动,飞轮盘和摩擦片会在一定时刻形成相互咬合的状态.离合器黏滑振动的频率和系统的自然频率非常接近,受到系统结构的影响.当法向载荷从1.0 MPa增大到1.5 MPa时,系统振动位移信号的波动幅值增大,黏滑振动周期减小,系统颤振现象更加明显.但当法向载荷进一步增大到3.0 MPa时,黏滑振动逐渐演变为持续的摩擦自激振动现象.通过合理地调控离合器接合的法向载荷,有利于改善黏滑振动现象.摩擦片厚度对系统黏滑振动特性的影响显著,当摩擦片厚度从2 mm逐渐增加为4 mm时,系统的结构频率发生变化,从而使得系统黏滑振动的频率发生变化.此外,增大摩擦片厚度能够改善系统黏滑振动行为,降低系统黏滑振动强度,因此适当地增大摩擦片厚度,是改善黏滑振动强度的有效手段.     

摩擦离合器黏滑振动特性的显式动力学分析

针对摩擦离合器在接合过程中出现的黏滑振动问题,建立了某车型离合器三维有限元模型,通过采用有限元软件ABAQUS内嵌的显式动力学分析算法,对离合器系统在接合过程中产生的黏滑振动特性进行研究,通过改变法向载荷和摩擦片厚度,探讨了两者对离合器系统黏滑振动行为的影响.研究结果表明,利用ABAQUS显式动力学分析能有效地模拟出离合器接合过程中产生的黏滑振动现象.黏滑振动发生过程中,系统位移信号呈现出明显的锯齿状波动,飞轮盘和摩擦片会在一定时刻形成相互咬合的状态.离合器黏滑振动的频率和系统的自然频率非常接近,受到系统结构的影响.当法向载荷从1.0 MPa增大到1.5 MPa时,系统振动位移信号的波动幅值增大,黏滑振动周期减小,系统颤振现象更加明显.但当法向载荷进一步增大到3.0 MPa时,黏滑振动逐渐演变为持续的摩擦自激振动现象.通过合理地调控离合器接合的法向载荷,有利于改善黏滑振动现象.摩擦片厚度对系统黏滑振动特性的影响显著,当摩擦片厚度从2 mm逐渐增加为4 mm时,系统的结构频率发生变化,从而使得系统黏滑振动的频率发生变化.此外,增大摩擦片厚度能够改善系统黏滑振动行为,降低系统黏滑振动强度,因此适当地增大摩擦片厚度,是改善黏滑振动强度的有效手段.     

滑动摩擦振动噪声的非线性显式动力学分析

利用有限元软件ABAQUS/Explicit(显式动态求解器)对球-平面接触条件下的滑动摩擦振动噪声进行了数值模拟分析。对比试验结果,探讨了摩擦噪声的发生机制,并分析了摩擦噪声发生时接触界面的运动特性。结果表明,摩擦噪声主要是由摩擦系统的自激振动引起的,法向振动与切向振动的耦合是系统产生自激振动和摩擦噪声的一个重要因素。当摩擦系统发生自激振动时,从面节点与主面的接触并不是连续不变的,两者在相对运动的过程中具有黏着-滑动-分离-黏着的特性。     

摩擦式螺旋压力机离合器特性分析

本文充分阐述了摩擦式螺旋压力机的关键技术－离合器,分析了离合器的结构特点、工作原理,尤其分析了对压力加工形成的影响,这对于正确认识和深刻理解摩擦式螺旋压力机的本质特征,有着重要的指导意义。     

变截面超越弹簧离合器结合过程动力学特性分析

分析了超越弹簧离合器的工作原理,揭示了变截面弹簧离合器结合过程运动与动力学特性为。在建立超越弹簧离合器有限元模型及加载边界条件基础上,分析了离合器结合过程中弹簧扩张及各圈应力变化规律。得到了弹簧/壳体接触力分布特征和离合器结合时间、输出壳体与输入壳体速度跟随特性,以弹簧在非稳态—稳态过程中径向各点Mises应力和弹簧内外圈应力变化规律。论文研究为离合器结构、参数设计和故障分析提供了依据。     

自动加压式摩擦离合器的稳定性分析

本文对新型的自动加压式摩擦离合器在额定载荷下及干扰力矩下的稳定性作了动态分析,建立了稳定性的数学物理模型,求得了稳定性的条件,为设计自动加压式摩擦离合器提供了理论依据。     

界面黏滑摩擦现象的研究进展

从宏观尺度和微观尺度两个方面介绍了界面黏滑摩擦的研究进展,重点概述了宏观黏滑现象及其摩擦特性、微观黏滑现象及其摩擦特性、黏滑摩擦的建模以及黏滑实验研究进展,分析了现阶段界面黏滑摩擦研究中的重点问题。最后指出,从微观和介观尺度上研究界面摩擦行为是黏滑摩擦的未来发展方向。     

汽车离合器接合过程中的摩擦振动行为分析

建立了离合器摩擦系统全尺寸模型,基于有限元软件ABAQUS的复特征值分析法和瞬时动态分析法研究了离合器接合过程中的摩擦振动现象,探讨了界面参数对离合器稳定性的影响和作用机理。结果表明,离合器接合过程中的振动模态主要表现为摩擦片的面外振动,通过削弱界面黏滑运动、提高界面摩擦因数和在摩擦片表面加工沟槽等手段能有效地改善摩擦振动,增强离合器接合稳定性。     

浮块式摩擦离合器及装配

浮块式摩擦离合器（见图1）广泛应用于各种锻压设备，如热模锻压力机及双点压力机、棒料剪切机、辊锻机等。一、结构特点及动作原理浮块式摩擦离合器结构简单，尺寸紧凑。整个离合器固定在飞轮A上，摩擦盘G通过胀套E或楔形键与传动轴F紧紧地联接成一体，随传动轴一起转动或停止。摩擦盘上设有安装摩擦块B的孔。离合器外壳D内装有活塞C，它是离合器的主要传力元件。这种离合器是由电、气系统控制的。飞轮A的外缘设有齿轮轮齿或三角皮带槽，电机通过齿轮或三角皮带带动飞轮A旋转。当需要离合器“合上”时，压力为0．55MPa～0．6MPa的压…     

阻尼参数对摩擦系统稳定性及黏滑运动的影响

基于普遍的销?盘摩擦系统,建立了一个同时考虑摩擦界面的法向与切向振动的非线性四自由度数学模型,基于复特征值分析法和时域分析法研究了系统法向和切向阻尼值对系统稳定性的影响。对系统的雅各比矩阵的复特征值分析表明：法向和切向阻尼值会对系统临界摩擦因数产生重要影响,系统存在一个最优阻尼比使系统的稳定性达到最强。在选取合理阻尼比值的基础上,若同时增大法向和切向的阻尼值有利于进一步提高系统的稳定性,减少摩擦系统不稳定振动的倾向。通过数值模拟计算,在进一步考虑黏滑现象的基础上,对系统动力学行为进行时域分析。结果表明：系统的振动行为会经历振幅增大的滑动阶段、振幅增大的黏滑运动阶段和纯黏滑阶段;同时在低速状态下,系统阻尼值会对振动极限环及黏着时长产生重要影响。     

Some considerations of slideway friction characteristics by observing stick-slip vibration

It is important to clarify the frictional characteristics of a slideway and to prevent unstable vibration, such as stick-slip vibration, for the improvement of kinematic performance and for precise positioning. In this research, the relations among the dynamic friction characteristics, the pitching motion or the floating up of the slider, the surface roughness of a slideway, and the lubricant property are investigated experimentally. As a result, some points necessary for the kinematic performance improvement of the slider are clarified.     

Normal displacement and dynamic friction characteristics in a stick-slip process

The dynamic friction-velocity relationship in the slip stage of stick-slip vibration was investigated with a pin-on-flat apparatus. A reasonable relationship was derived from the measured displacement and acceleration of the sliding element, using a computing technique which provided smooth, reliable curves. It was found, from an examination of the effect of data smoothing on computed friction characteristics, that the moving average method can be recommended. Variation of normal displacement of the sliding body during the slip period was examined together with tangential displacement and electrical contact resistance. The friction-velocity relationship was well explained by an assumption that the instantaneous friction variation results from the change in real area of contact resulting from normal displacement occuring in an elastic contact.     

Research and experimental analysis of drill string dynamics characteristics and stick-slip reduction mechanism

Stick-slip of the drill string, as one of the critical factors affecting drilling efficiency, has always been a hot topic for experts and scholars in related fields. Serious stick-slip vibration affects the well construction efficiency, drilling cost and even lead to a downhole accident. Therefore, based on the current research, this paper takes a new type of composite vibration tool as the research object, studies the working mechanism of the tool and analyzes the effect of stick-slip reduction. After establishing the multi-degree-of-freedom torsional dynamics model, we obtained the results of torsional vibration dynamics by cases analysis based on working conditions and related mechanical parameters. In addition, the results of the examples, compared with the field experimental data, verify that the vibration shock generated by the new composite tool can effectively reduce the torque fluctuation range of the system, avoid the occurrence of stick-slip phenomenon, improve the ROP (rate of penetration), and make drilling process more stable. This paper can provide reference for the optimization and development of stick-slip technology in drilling engineering, and the theoretical methods can also be developed to study the dynamics of drill string.     

Acoustic output from stick-slip friction

An investigation into the correlation between the friction characteristics produced during stick-slip motion and the noise and vibration of a loading system caused by the frictional contact is presented. Various material combinations at the contact have produced distinctly different friction characteristics.Results show the presence of acoustic signals in some contact combinations and not in others. At this stage the reasons for this are not fully understood, but some common underlying trends are discussed.     

Study on slip displacement and stick-slip characteristics in reciprocating friction drive system

The effects of follower mass, time ratio, driver speed, and normal load on the slip displacement and stick-slip characteristics are experimentally and theoretically investigated in the reciprocating friction drive system under dry contact using a 0.45% carbon steel pair. Results show that the accumulative slip displacement is linearly proportional to the rotating cycle under various operating conditions. The slope for this linear relationship is defined as the slip rate. The slip rate increases with increasing driver speed, the mass of the follower, and |δ−1|, but decreasing normal load. There are three modes of relative motion between the driver ring and the follower in the present study, namely, unstable stick-slip (USS), stable stick-slip (SSS), and sticking (ST) regimes. They are significantly influenced by the driver speed, normal load, time ratio and mass of the follower. The critical operating conditions among unstable stick-slip, stable stick-slip, and sticking regimes were also established. The critical frequency can be theoretically calculated and agrees well with experimental results.     

非平面摩擦离合器

介绍一种非平面摩擦离合器,该离合器的当量摩擦系数为一般摩擦离合器摩擦系数的10～30倍以上,具有体积小,传递扭矩大,且结构简单、工艺性好、造价低廉、寿命长的优点,是一种较为理想的新型摩擦离合器。     

Influence of surface topography on friction characteristics in wet clutch applications

In heavily loaded wet clutches, such as in limited slip differentials, sintered friction materials are sometimes used due to their resilience at high loads and high temperatures as well as their competitive cost in comparison to alternative friction materials.During the lifetime of the clutch, changes in the friction materials’ topography occur. These changes will influence the friction characteristics of the clutch, and therefore affect the anti-shudder performance of the transmission system. This paper investigates the influence of, and classifies, changes in the topography of the sintered friction material.The topography is measured by utilizing vertical scanning interferometry. Different parameters are investigated in order to find relevant parameters correlating to the wear of the material.Results show that changes in the topography of the friction material do indeed influence the friction characteristics of the clutch and that it is possible to calculate relevant topography parameters that describe the amount of wear the material has been subjected to.     

Numerical analysis of stick-slip instability by a rate-dependent elastoplastic formulation for friction

In various fields of engineering, it is important to clarify friction-induced vibration, such as stick-slip motion, for a wide range of scales from microscopic elements to continental plates. In the present study, we apply a rate- and state-dependent friction model [30] (Hashiguchi and Ozaki, 2008), which can rationally describe the reciprocal transition between the static friction and the kinetic friction by a unified formulation, to the simulation of stick-slip instability for a one-degree-of-freedom spring-mass system under various conditions. It is verified that the various basic experimental findings on stick-slip motion can be pertinently described by the present approach. Moreover, the effect of the dynamic characteristics of the system, such as the mass, stiffness and driving velocity, is discussed, and parameters prescribing the rate of reciprocal transition of static-kinetic frictions and the preliminary microscopic sliding on the instability of the stick-slip motion are also discussed.