车轮多边形激励下高速列车制动界面摩擦学行为分析

高速列车车轮多边形磨耗是一种沿车轮周向的不均匀磨耗,是列车服役过程中常见的车轮失效现象,其产生的剧烈轮轨激励严重威胁车辆系统服役可靠性. 制动系统作为保障高速列车服役安全的核心部件,其界面摩擦学行为直接受到轮轨激励的影响. 为探究车轮多边形激励下的制动界面摩擦学行为,建立了刚柔耦合车辆动力学模型和制动系统热机耦合有限元模型,并分别通过线路试验和台架试验验证了模型的正确性. 然后,提出一种考虑车轮多边形激励的制动界面摩擦学行为分析方法,能够真实地反映服役过程中制动界面摩擦学行为. 基于此,研究了不同车辆运行速度下车轮多边形激励对制动系统动态接触、温度以及振动特性的影响规律. 结果表明:车轮多边形磨耗导致系统接触面积、摩擦热、接触应力和振动等摩擦学行为更为复杂且剧烈. 此外,系统接触面积标准差和振动加速度均方根值随速度的增加而增大. 因此,车轮多边形磨耗对制动界面摩擦学行为具有不可忽略的影响. 该研究成果可为制动系统界面摩擦学行为研究及结构优化设计提供有效方法与工程指导.      

The influence of the brakes friction elements thickness on the contact temperature and wear

This paper is the continuation of the author's investigations [11] where the mathematical model for determination of the contact temperature, sliding speed and wear during braking was proposed. On contrary to the previous investigation, where the working elements were considered as the half-spaces, at the present paper their thickness is taken into account. For three different dependences of the friction coefficient upon the temperature the influence of thickness on the contact temperature and wear is studied. Received on 26 April 1999     

高速列车制动闸片摩擦块形状对制动界面摩擦学行为的影响

在自行研制的高速列车制动缩比试验台上,对六边形、五边形和圆形摩擦块进行拖曳制动试验,研究摩擦块形状对高速列车制动界面摩擦学行为的影响,并采用有限元方法分析了不同摩擦块形状下制动界面接触行为的差异,探讨了摩擦块形状对接触压力分布及表面热分布的影响. 结果表明:摩擦块形状显著影响了制动界面磨损特性及接触压力分布,使得制动盘产生不同的温度分布现象. 在本试验条件下,六边形摩擦块表面磨损轻微,接触平台大小较为均匀,而五边形和圆形摩擦块表面呈现明显的犁沟和剥落特征,且大接触平台占比较高;六边形摩擦块与制动盘拖曳制动过程,界面具有较大的接触面积,使得接触压力分布较为均匀,表现出较好的接触行为,而五边形和圆形摩擦块的接触行为相对较为复杂,与之对摩的制动盘产生明显的热聚集现象.      

Influence of the temporal profile of the contact pressure on the maximal temperature in pad/disc tribosystem

The solution to a thermal problem of friction during braking for a pad/disc (strip/semi-space) tribosystem with a time-dependence upon friction power is obtained. The convective cooling on an upper surface of a strip and the heat transfer through a contact surface are considered, too. The influence of duration of increase in pressure from zero (at the initial moment of time) to nominal value (at the moment of a stop) on the maximal temperature for a friction pair metal-ceramic pad/cast iron disc is studied.     

制动工况对汽车半金属刹车片磨损性能的影响

刹车片是汽车制动器的重要部件材料,其磨损特性直接影响制动器工作性能和使用寿命,现有研究主要采用小样试验,不能真实反映刹车片实际使用工况. 采用汽车盘式制动器模拟制动试验台,分析了制动初速度、制动压力、摩擦面温度对刹车片磨损的影响规律. 结果表明:随制动压力、制动初速度或摩擦面温度的增大,磨损量曲线均呈上升趋势,其中制动压力的变化对磨损量的影响较小,制动初速度的变化对其影响最大. 通过几组补充试验得到,没有外界热源干预,制动初速度和制动压力共同作用比摩擦面温度对磨损量的影响更明显. 基于试验结果数据,利用SPSS软件拟合了制动工况参数与磨损量之间的经验公式. 研究结果对于指导汽车刹车片的设计制造和使用维护具有一定理论意义和实用价值.      

Thermo-mechanical contact behavior of a finite graded layer under a sliding punch with heat generation

The problem of a rigid punch contacting with a finite graded layer on a rigid substrate is investigated within the framework of steady-state plane strain thermoelasticity, in which heat generated by contact friction is considered with a constant friction coefficient and inertia effects are neglected. The material properties of the graded layer vary according to an exponential function in the thickness direction. Fourier integral transform method and transform matrix approach are employed to reduce the current thermocontact problem to the second kind of Cauchy-type singular integral equation. Distributions of the contact pressure and the in-plane stress under the prescribed thermoelastic environment with different parameter combinations, including ratio of shear moduli, relative sliding speed, friction coefficient and thermal parameters are obtained and analyzed, as well as the stress singularity and the stress intensity factors near the contact edges. The results should be helpful for the design of surfaces with strong wear resistance and novel graded materials for real applications.     

洛伦兹力与温度场作用下枢轨摩擦磨损特性

电枢与轨道间摩擦磨损直接影响着枢轨接触状态,进而影响着电磁轨道发射装置的使用寿命和发射效率. 因此针对焦耳热与摩擦热作用下接触面温度纵向扩散特性,建立温度作用下Archard磨损模型分析温度对枢轨间磨损的影响. 结果表明:枢轨间磨损量主要发生在电枢表面,且最大磨损量集中在电枢尾翼边缘区域. 随着电枢运动过程,枢轨表面温度逐渐升高,接触区域材料的弹性模量和硬度降低,枢轨间磨损量增大. 接触表面磨损量增大也反映出了枢轨接触面温度升高加速了电枢表面的烧蚀.      

制动磨损源大气颗粒物排放的研究进展

交通运输工具种类及数量的持续增长,势必会给环境保护带来严重的影响. 交通运输工具于摩擦制动过程释放的制动磨损颗粒物(即制动粉尘)已成为城市大气颗粒物的重要贡献源,显著影响着城市的空气质量. 为贯彻落实绿色发展理念,探索制动磨损源大气颗粒物排放的控制措施,需深入了解颗粒物排放的准确信息. 基于此,本文中综述了近年来以制动磨损为源头的大气颗粒物排放研究进展. 首先,从机理层面介绍了制动过程中磨屑的衍化,简述了摩擦层的形成机制和制动粉尘的来源及排放特性;其次,重点阐述了制动器结构、材料类型、外界环境、制动速度和制动载荷等因素对制动磨损源大气颗粒物排放的影响,分析了各因素对大气颗粒物排放特性(如颗粒形貌、颗粒尺寸和颗粒浓度等)的影响规律;最后,提出了制动磨损源大气颗粒物排放研究需要加强的几方面内容.      

固体润滑剂摩擦学特性的强化试验装置

作者对原有四球机进行了局部的重新设计,将试样的点接触形式改成了面接触形式,并且增加了冷却系统,使下试样下部浸在循环冷却液中相对滑动,有效地抑制了高速重载强化试验条件下的摩擦温升。特殊的设计保证了平面与平面接触的充分贴合。试验结果表明,本装置对于不同的试样具有较好的灵敏性,对于相同的试样具有较好的重现性,因而试验结果比较可靠。     

Effect of time-dependent speed on frictional heat generation and wear in transient axisymmetrical contact of sliding

Summary A transient contact problem with frictional heating and wear for two nonuniform sliding half-spaces is considered. One of the two half-spaces is assumed to be slightly curved to give a Hertzian initial pressure distribution: the other is a rigid nonconductor. Under the assumption that the contact pressure distribution could be described by Hertz formulas during all the process of interaction, the problem is formulated in terms of one integral equation of Volterra type with unknown radius of contact area. A numerical solution of this equation is obtained using a piecewise-constant presentation of an unknown function. The influence of operating parameters on the contact temperature and the radius of the contact area is studied. Accepted for publication 3 November 1996     

Temperature and stress analysis of an elastic circular cylinder in contact with heated rigid stamps

Summary  The present paper discusses a plane strain problem of transient thermoelasticity in a circular cylinder which is in partial contact with two heated rigid stamps, in the case where the coefficient of relative heat transfer on the contact surface of the cylinder is different from that on the traction-free surface. A finite difference method with respect to the time variable and Airy's thermal stress function is employed to analyze the temperature and thermoelastic fields. The problem is formulated in terms of two dual-series equations derived not only from the thermal boundary conditions but also from the mechanical boundary conditions. Since the radial, hoop and axial stresses have singularities at the end of the contact surface of the cylinder, the stress singularity coefficients are defined and then the relationship among these three coefficients is also obtained. Finally, numerical results are illustrated graphically. Received 3 March 2000; accepted for publication 12 July 2000     

Numerical study of sliding wear caused by a loaded pin on a rotating disc

A computational approach is proposed to predict the sliding wear caused by a loaded spherical pin contacting a rotating disc, a condition typical of the so-called pin-on-disc test widely used in tribological studies. The proposed framework relies on the understanding that, when the pin contacts and slides on the disc, a predominantly plane strain region exists at the centre of the disc wear track. The wear rate in this plane strain region can therefore be determined from a two dimensional idealisation of the contact problem, reducing the need for computationally expensive three dimensional contact analyses. Periodic unit cell techniques are used in conjunction with a ratchetting-based failure criterion to predict the wear rate in the central plane strain region. The overall three dimensional wear rate of the disc is then determined by scaling the plane strain wear rate with a conversion factor related to the predicted shape of the wear track. The approach is used to predict pin-on-disc test data from an Al-Si coating using a tungsten carbide pin. The predicted results are found to be consistent with measured data.     

摩擦粒子填充材料对高速列车闸片制动性能的影响

在自行研制的制动缩比试验台上,对中心孔填充不同材料的高速列车制动闸片摩擦粒子进行拖曳制动试验,并采用有限元分析方法进行制动系统复特征值和接触应力分析,探讨填充不同材料对磨损特性、振动噪声和热分布的影响. 结果表明:原始摩擦粒子中心孔填充材料后,对制动系统的摩擦系数和模态耦合特性未产生显著影响,但对界面磨损行为和系统振动噪声特性产生明显影响. 填充粉末冶金后排屑行为下降,磨损行为更为复杂,制动系统产生的噪声增大;而填充紫铜、石墨和铸铁后的制动噪声均有所降低,尤其填充铸铁后表面磨损相对均匀,其摩擦学性能相较于其他粒子得到一定的改善. 填充材料产生的磨屑及相应的界面磨损行为是影响制动摩擦振动噪声和表面热分布的关键因素,填充合理的材料有助于降低制动噪声和改善制动界面磨损行为及表面热分布.      

The thermoelastic Hertzian contact problem

A numerical solution is obtained for the steady-state thermoelastic contact problem in which heat is conducted between two elastic bodies of dissimilar materials at different temperatures with arbitrary quadratic profiles. Thermoelastic deformation causes the initially elliptical contact area to be reduced in size and to become more nearly circular as the temperature difference is increased. There is also a small but identifiable deviation from exact ellipticity at intermediate temperature differences. An approximate analytical solution is obtained, based on approximating the contact area by an ellipse.     

Convective heat transfer in a locally heated plane incompressible fluid layer

The problem of convection in a plane horizontal layer of incompressible fluid with rigid boundaries when the temperature is constant on the lower boundary and has a parabolic profile on the upper boundary can be reduced to solution of a system of time-dependent one-dimensional equations. An analytic solution of the problem is obtained directly at the extremum point. Together with the wellknown solutions which describe heat transfer for the linear temperature distribution on the boundaries, the results obtained make it possible to calculate the heat flux through a thin slit for an arbitrary given heating of a thin fluid layer between heat-conducting bodies.     

Analysis of heat conduction in a disk brake system

In this paper, the governing heat equations for the disk and the pad are extracted in the form of transient heat equations with heat generation that is dependant to time and space. In the derivation of the heat equations, parameters such as the duration of braking, vehicle velocity, geometries and the dimensions of the brake components, materials of the disk brake rotor and the pad and contact pressure distribution have been taken into account. The problem is solved analytically using Green’s function approach. It is concluded that the heat generated due to friction between the disk and the pad should be ideally dissipated to the environment to avoid decreasing the friction coefficient between the disk and the pad and to avoid the temperature rise of various brake components and brake fluid vaporization due to excessive heating.     

A nonlinear contact pressure distribution model for wear calculation of planar revolute joint with clearance

As various errors result from manufacture and assembly processes or wear effect, clearance joint widely exists in mechanical system as a base component. The coupling analysis of tribology and dynamics of clearance joint is important to the reliability of mechanical system. A nonlinear contact pressure distribution mode (NLCP) is proposed to combine dynamics analysis with wear calculation together in this paper. The discrete thought of Winkler model is adopted to deal with contact problem with a high conformal rate. The contact relationship in a local microcontact area can be regarded as the contact between cylinder and plane. And the local contact pressure is acquired based on Hertz contact theory. The NLCP model has not only described the nonlinear relationship between contact pressure and penetration depth, but also avoided the complexity in contact pressure computation. The performance of NLCP model is demonstrated in comparison with asymmetric Winkler model, revealing that NLCP model has enhanced the calculation accuracy with a good efficiency. A comprehensive experimental study on the wear calculation of a slider–crank mechanism with clearance joint is presented and discussed to provide an experimental verification for NLCP model. The paper’s work has solved the contact problem with a high conformal rate and has described the nonlinear relationship between contact pressure and penetration depth. It has great value to the wear analysis of clearance joint.     

考虑材料温度相关性的二维轮轨弹塑性滑动接触温升分析

轮轨滑动接触温升的准确预测对于轮轨的磨耗和疲劳研究均具有重要意义. 目前的轮轨温升解析或半解析模型通常考虑Hertz弹性接触压力分布和单一材料属性的温度相关性, 与实际的轮轨传热状态尚有一定偏差, 因此在轮轨滑动温升计算模型中考虑接触压力的塑性修正和多种材料属性的温度相关性, 有望提高温升预测结果的准确性. 基于弹塑性接触理论, 同时考虑热导率、比热容和摩擦系数的温度相关性, 通过基尔霍夫变换方法以热导率温度相关性函数的积分作为待求量, 将复杂的非线性Fourier导热方程转化成含单个变系数的简单偏微分方程形式, 从而构建了一种不限制材料温度相关性函数形式的统一隐式差分求解格式, 分别讨论了对流换热系数、法向载荷、蠕滑率以及行车速度对钢轨表面滑动温升的影响. 结果表明, 当列车高速行驶时, 对流换热系数对轮轨滑动温升的影响甚微; 蠕滑率和行车速度的增大, 均会引起摩擦功率的增大, 进而导致钢轨表面温度的升高; 钢轨表面滑动温升的峰值随法向载荷的增大而近似线性上升. 此外, 在轮轨滑动温升计算模型中考虑材料属性的温度相关性可有效避免对滑动温升的过分高估, 且摩擦系数的温度相关性对温升的影响要显著强于热导率和比热容.      

FRICTIONAL TEMPERATURE ANALYSIS OF TWO-DIMENSIONAL ELASTO-PLASTIC WHEEL-RAIL SLIDING CONTACT WITH TEMPERATURE-DEPENDENT MATERIAL PROPERTIES 1)

轮轨滑动接触温升的准确预测对于轮轨的磨耗和疲劳研究均具有重要意义. 目前的轮轨温升解析或半解析模型通常考虑Hertz弹性接触压力分布和单一材料属性的温度相关性, 与实际的轮轨传热状态尚有一定偏差, 因此在轮轨滑动温升计算模型中考虑接触压力的塑性修正和多种材料属性的温度相关性, 有望提高温升预测结果的准确性. 基于弹塑性接触理论, 同时考虑热导率、比热容和摩擦系数的温度相关性, 通过基尔霍夫变换方法以热导率温度相关性函数的积分作为待求量, 将复杂的非线性Fourier导热方程转化成含单个变系数的简单偏微分方程形式, 从而构建了一种不限制材料温度相关性函数形式的统一隐式差分求解格式, 分别讨论了对流换热系数、法向载荷、蠕滑率以及行车速度对钢轨表面滑动温升的影响. 结果表明, 当列车高速行驶时, 对流换热系数对轮轨滑动温升的影响甚微; 蠕滑率和行车速度的增大, 均会引起摩擦功率的增大, 进而导致钢轨表面温度的升高; 钢轨表面滑动温升的峰值随法向载荷的增大而近似线性上升. 此外, 在轮轨滑动温升计算模型中考虑材料属性的温度相关性可有效避免对滑动温升的过分高估, 且摩擦系数的温度相关性对温升的影响要显著强于热导率和比热容.     

The fundamental equations in finite element method of coupled thermo-elastic plane problem

The fundamental equations in finite element method for unsteady temperature field elastic plane problem are derived on the bases of variational principle of coupled thermoelastic problems. In these derivations, elastic plane is divided into three nodes triangular elements, and time interval is divided into linear time elements, in which all the variables, including displacements and temperatures at various nodal points, are varied linearly with time. Two coupled sets of linear algebraic equations of all the unknown displacements and temperatures at every nodal point in every instant (i.e. the terminal values of time elements) are obtained. They are the fundamental equations of the said problem.The total energy in elastic body not only contains the potential energy and heat energy but also contains the kinetic energy, if the rate of change of temperature field with respect to the time in thermoelastic problem is large enough. And the change of displacement is included in the equations of heat conduction. For this reason the variational principle of coupled thermoelastic problems is employed. [1] In this paper, expressions of this principle for plane problems are given. The discretization is carried on then, and Hamilton's action and the potential action of heat flow of elements are derived. Finally they are assembled, so as to get the polar value of the action. And thus the groups of linear algebraic equations in matrix form are obtained.