高速列车车轮踏面磨耗预测方法的研究

高速铁路的发展满足日益增长的运输需求,同时带来了轮轨型面磨损问题.通过磨耗预测模型对车轮踏面磨耗量进行预测,及时对磨损的车轮踏面进行镟修,对于列车安全运行具有重要意义.通过建立轮对-钢轨三维有限元模型进行接触计算,提出一种基于有限元算法的摩擦功计算方法,即接触节点的摩擦功等于接触摩擦力与节点相对位移的乘积,实现车轮踏面磨耗预测.通过接触计算,发现接触斑中心处的接触摩擦力较大,相对位移量较小,摩擦功较小;将接触斑摩擦功叠加得到车轮踏面摩擦功,数值曲线呈中部大边缘小,且随牵引力的增大而增大;通过动力学计算,发现列车在直线钢轨运行初期的车轮横移量近似呈正态分布;对列车在直线钢轨上运行不同里程的车轮踏面进行磨耗预测,发现预测型面与实测型面具有相同的磨耗趋势,即车轮名义滚动圆处磨耗最严重,且磨耗宽度随列车运行里程增加而逐渐增大;应用有限元法计算磨耗功并预测车轮踏面磨耗,具有一定的研究意义和实用价值.     

轮轨滚动摩擦温升分析

利用有限元法,考虑轮轨间非稳态热传导、与环境的热对流以及热辐射的影响,建立了轮轨滚动接触热耦合计算模型来模拟轮轨滚滑摩擦温升;在模拟轮轨纯滑动条件下,计算分析了由磨损引起的滑动接触斑的尺寸增大对轮轨温度场的影响;在模拟轮轨接触斑部分滑动工况时,针对不同蠕滑率、摩擦系数以及轴重对轮轨温度场的影响进行了相应的计算分析.结果表明:接触斑材料的磨损速度只影响磨损过程中的温度场分布,其稳态温度场分布基本一致;热载荷随着纵向载荷、蠕滑率以及摩擦系数的增大而增大,进而影响轮轨滚动接触热疲劳.     

基于有限元法的轮轨蠕滑特性研究

轮轨滚动接触蠕滑率／力理论是轮轨相互作用一系列问题研究的基础．现有的几种计算蠕滑力的理论模型均建立在Hertz接触条件和半空间假设的基础上，已经无法完成对复杂的接触问题的进一步研究．使用有限元参数二次规划法来求解轮轨的三维弹性／弹塑性接触问题，得出了在不同的轴重、牵引力矩、摩擦系数、踏面形状、横向力条件下的轮轨接触力．提出用轮轨接触的轮周位移计算蠕滑率的新方法，并对在各种参数下所得到的蠕滑率进行了分析比较．     

高速列车车轮磨耗预测仿真

为了研究高速列车车轮磨耗问题,建立了车辆多体系统动力学和车轮磨耗耦合模型.模型中考虑了车辆系统悬挂非线性?轮轨接触几何非线性和轮轨蠕滑力非线性.采用数值仿真方法研究车轮型面的磨耗分布和发展.考虑车辆通过一条由直线和不同曲线组成的典型线路,通过动力学仿真计算轮轨接触情况,采用FASTSIM计算轮轨接触斑上车轮磨耗量,进行车轮型面磨耗量的累积和型面外形更新,然后再进入下一个磨耗循环的计算.通过比较分析,选择车轮型面垂直磨耗0.1mm为型面更新的条件,分别采用Archard磨耗模型?基于摩擦功的磨耗模型和基于磨耗指数的磨耗模型来预测车轮型面磨耗发展情况.并与测量得到的车辆实际线路运行中车轮磨耗量进行了比较.结果表明,仿真得到的车轮型面磨耗发展情况和实际测量结果趋势相同,其中基于磨耗功和磨耗指数模型的计算结果接近,而Archard模型算得的轮缘磨耗相对较大.因此,可以根据具体线路有针对性地选择磨耗模型,通过仿真方法预测车轮型面的磨耗,为高速列车的安全可靠运行提供指导.     

轮轨滚动接触力学的发展

轮轨滚动接触力学主要研究轮轨滚动接触过程中的作用行为。由于其研究的复杂性,目前在该领域的研究已基本形成既独立又关联的六个分支,它们分别是轮轨滚动接触蠕滑率/力理论、轮轨粘着、接触表面波浪形磨损、轮轨滚动疲劳、脱轨和轮轨噪音。本文综述了这几个方面研究的发展历史和现状。由于轮轨滚动接触作用的研究又是以轮轨滚动接触蠕滑率/力理论为基础的,故本文着重评述目前常用于车辆/轨道动力学和轮轨关系研究中几个经典滚动接触理论模型的优缺点。根据实际工程中轮轨作用存在的严重问题,并提出轮轨滚动接触理论及其试验在今后的研究方向和所要考虑的有关重要因素。      

轨下支承失效对直线轨道动态响应的影响

建立了基于Timoshenko梁模型的车辆/轨道耦合动力学模型,分析轨下支承失效对直线轨道动态响应的影响. 钢轨被视为连续弹性离散点支承上的无限长Timoshenko梁,通过假设轨道系统刚度沿纵向分布发生突变来模拟轨下支承失效状态. 推导了考虑钢轨横向、垂向和扭转运动的轮轨滚动接触蠕滑率计算公式. 利用Hertz法向接触理论和沈氏蠕滑理论计算轮轨法向力及轮轨滚动接触蠕滑力. 采用移动轨下支承模型的车辆/轨道耦合系统激振模式,考虑轨枕离散支承对系统动力响应的影响. 通过新型显式积分法求解车辆/轨道耦合动力学系统运动方程,由数值分析计算得到不同轨下支承失效状态下直线轨道的动态响应. 结果表明,轨下支承失效对直线轨道变形及加速度有显著的影响,随着失效轨下支承个数的增加,轮轨相互作用力和轨道部件的位移、加速度将会急剧增大,将加速失效区段线路状况的恶化.      

基于有限元的高速列车车轮多边形磨耗成因分析

研究了中国高速列车车轮多边形磨耗的形成原因,考虑轮对的旋转惯量,建立了高速列车轮对-轨道-盘式制动系统有限元模型. 基于轮轨系统摩擦自激振动的理论,采用有限元复特征值分析法研究了高速列车制动时轮对-轨道-盘式制动系统的稳定性. 研究了饱和的轮轨蠕滑力和盘式制动系统摩擦力耦合作用对车轮多边形磨耗的影响,并调查了轮轨-轨道-盘式制动系统的参数敏感性. 数值模拟结果表明:在饱和的轮轨蠕滑力和盘式制动器摩擦力耦合作用下,轮轨系统的摩擦自激振动导致高速列车车轮多边形磨耗的产生,其导致的21~22阶和23~24阶车轮多边形磨耗占主导地位,这与中国高速列车高阶车轮多边形磨耗最为符合. 饱和的轮轨蠕滑力主要影响较低阶车轮多边形磨耗,盘式制动器摩擦力主要影响较高阶车轮多边形磨耗. 制动压力为13 kN时,车轮多边形磨耗形成的几率最小,发展速度最慢. 过高或者过低的垂向悬挂力均不利于抑制车轮多边形磨耗. 垂向悬挂力为75 kN时,车轮多边形磨耗形成的可能性最小,发展速度最慢.      

应用于高速轮轨滚动接触的蠕滑理论算法对比研究

运用多体动力学仿真软件UM建立了车辆-轨道多体动力学模型，并基于轮轨滚动蠕滑理论对比分析了FASTSIM算法与CONTACT算法两者在稳态和瞬态滚动状态中轮轨动态作用力之间的差异.计算结果表明:列车以稳态滚动状态行驶在直线轨道和曲线轨道上时通过FASTSIM算法计算得出的横、纵向轮轨蠕滑力与CONTACT算法的计算值存在的差异值较小，达到了10%~15%，而在瞬态滚动状态下尤其是在大蠕滑以及考虑风阻等比较恶劣的工况下行驶时计算得出的横、纵向蠕滑力与CONTACT算法的计算值存在较大的误差，差值达到了25%，并且随着车速的增加，最大差异值达到了30%，这表明CONTACT算法在瞬态滚动工况下进行蠕滑力计算上相比于FASTSIM算法更加精准，更适用于作出对列车运行时的安全性方面的评价.      

曲线半径对钢轨磨损影响的数值计算与试验分析

用数值计算方法详细分析了静态接触情况下,轮轨接触质点间蠕滑力、黏滑区的分布和摩擦功随曲线半径的变化,利用模拟试验研究了曲线半径对钢轨试样磨损特性的影响.结果表明:钢轨磨损量随曲线半径的增大呈非线性减小,在小于1 200 m的小曲线半径范围内,钢轨磨损量值随曲线半径的减小而急剧增大;随着曲线半径的增大,轮轨接触斑中最大滑动量逐渐减小,滑移区的面积减小,而黏着区的面积增大;轮轨接触斑上摩擦功随曲线半径的增大呈非线性的减小.     

小半径曲线科隆蛋扣件地段钢轨波磨特性

为研究小半径曲线科隆蛋扣件轨道的波磨演化特征,首先通过分析钢轨波磨实测数据,获得了波磨的典型通过频率;然后运用车辆-轨道空间耦合模型和基于摩擦功理论的钢轨材料摩擦磨损模型,对曲线段钢轨波磨特性进行了分析。结果表明:导向轮可承载的外侧蠕滑力几乎全程达到饱和,内侧蠕滑力部分达到饱和,且饱和部分呈周期性出现;当蠕滑力等于饱和蠕滑力时,磨耗深度最大,并且内轨的磨耗深度幅值大于外轨。结合钢轨磨耗预测型面可知,外轨主要发生侧磨,内轨则趋向发生波磨,从而出现内轨波磨严重而外轨波磨轻微这一现象。磨耗频域特性分析表明,内轨磨耗等级含有与实测波磨通过频率相近的特征频率,且这些频率处的磨耗增长率较大,说明对应频率的磨耗将不断发展,最终形成波磨。     

Effect of a scratch on curved rail on initiation and evolution of plastic deformation induced rail corrugation

A calculation model is put forward to analyze the effect of a scratch on the running surface of a curved rail on initiation and growth of plastic deformation induced rail corrugation when a wheelset is steadily and repeatedly curving. The numerical method considers a combination of Carter’s two-dimensional contact theory, a two-dimensional elastic–plastic finite element model and a vertical dynamics model of railway vehicle coupled with a curved track. A concept of feedback between the corrugation development and the vertical coupling dynamics of the wheelset and track is involved. The cyclic ratchetting effect of the rail material under repeated contact loadings is taken into account. The numerical results indicate that when a vehicle runs on rails with a scratch the contact vibration between the wheel and rail occurs at large amplitude, and rail corrugation due to plastic deformation initiates and develops. The corrugation has a tendency to move along the running direction and its evolution rate decays as wheelset passages increase. The passing frequencies of the plastic deformation induced corrugation depend on the natural frequencies of the track. The residual stresses stabilize after a limited number of wheelset passages. The residual strains increase at a reduced rate with increasing wheelset passages.     

Stability of the rectilinear motion of a railway Wheelset

A railway wheelset rolling on rails without slip is studied with consideration of the creep hypothesis. The wheelset is represented by two cones having a common base; the rails are represented by two circular cylinders with parallel axes. The kinematic characteristics of undisturbed rolling for the wheelset are determined when its center of mass moves along a straight line; these characteristics are also determined in the case of disturbed motion when the mass center of the wheelset moves along a sinusoidal trajectory. For these modes of motion, the constraint reactions are found with an accuracy up to the second order of smallness with respect to the values of disturbed variables. When the absolutely rigid point contact is replaced by the elastic contact, the creep hypothesis is used, the method of averaging with respect to the fast variables is applied, and a critical velocity above which the rectilinear rolling becomes unstable is determined on the basis of the averaged equations.     

Medium frequency dynamic investigation of the railway wheelset-track system using a discrete-continuous model

Summary In the paper, dynamic interaction between elastic high-speed-train car wheelset and track is studied using a discrete-continuous mechanical model. The model enables to investigate the influence of the parametric excitation from the track as well as static and dynamic unbalances of wheels and brake disks on the dynamic response of the wheelset running at various speeds on the track of various average vertical stiffness. From the results of numerical simulation it follows that particularly severe periodic resonances occur for the track of large stiffness, yielding high vertical dynamic contact forces between the wheels and rails. The maximum dynamic response has been obtained for parameters corresponding to the conditions at which the phenomenon of grumbling noise generation is usually observed in reality. Received 21 January 1997; accepted for publication 29 February 1997     

Track dynamic behavior at rail welds at high speed

As a vehicle passing through a track with different weld irregularities, the dynamic performance of track com- ponents is investigated in detail by using a coupled vehi- cle-track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are dis- cretely supported by sleepers. In the track model, the sleepers are modeled as rigid bodies accounting for their vertical, lat- eral and rolling motions and assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the study of the coupled vehicle and track dynamics, the Hertizian contact theory and the theory proposed by Shen-Hedrick-Elkins are, respectively, used to calculate normal and creep forces between the wheel and the rails. In the calculation of the normal forces, the coefficient of the normal contact stiffness is determined by transient contact condition of the wheel and rail surface. In the calcu- lation of the creepages, the lateral, roll-over motions of the rail and the fact that the relative velocity between the wheel and rail in their common normal direction is equal to zero are simultaneously taken into account. The motion equations of the vehicle and track are solved by means of an explicit integration method, in which the rail weld irregularities are modeled as local track vertical deviations described by some ideal cosine functions. The effects of the train speed, the axle load, the wavelength and depth of the irregularities, and the weld center position in a sleeper span on the wheel-rail impact loading are analyzed. The numerical results obtained are greatly useful in the tolerance design of welded rail pro- file irregularity caused by hand-grinding after rail welding and track maintenances.     

Boundary element method for moving and rolling contact of 2D elastic bodies with defects

A scheme of boundary element method for moving contact of two-dimensional elastic bodies using conforming discretization is presented. Both the displacement and the traction boundary conditions are satisfied on the contacting region in the sense of discretization. An algorithm to deal with the moving of the contact boundary on a larger possible contact region is presented. The algorithm is generalized to rolling contact problem as well. Some numerical examples of moving and rolling contact of 2D elastic bodies with or without friction, including the bodies with a hole-type defect, are given to show the effectiveness and the accuracy of the presented schemes. The project supported by the National Natural Science Foundation of China (19772025)     

谐波型波磨激扰下轮轨系统接触蠕滑特性

将钢轨波浪形磨耗理想化为三种波长和波深组合的连续谐波激扰，通过多体动力学软件UM，分析不同波长和波深工况下谐波激扰对轮轨接触蠕滑特性的影响。研究表明，当波长固定、波深增大时，钢轨轮对垂向振动加速度和纵向蠕滑率/力的平均值均增大，横向蠕滑率/力平均值均减小。当波深固定、波长增大时，钢轨轮对垂向振动加速度平均值和纵向蠕滑率/力平均值均减小，横向蠕滑率/力平均值均增大。纵横向蠕滑率/力均含有与初始不平顺频率值相接近的特征频率成分，纵向蠕滑率/力特征频率随着波深的增大趋向高频段发展，横向蠕滑率/力特征频率集中在低频段，且随着波深增大逐渐减小。当波深为0.3 mm时，纵横向蠕滑率/力强度相当，能量主要集中在低频，频率比较单一；当波深达到0.6 mm和0.9 mm时，蠕滑率/力以纵向蠕滑率/力为主，表现出多频率特征。在波长相同的条件下，随着运营时间的增加，磨耗量在低频段增加较小，在中高频段增加较大。     

Effect of rail corrugation on vertical dynamics of railway vehicle coupled with a track

The effect of rail corrugation on the vertical dynamics of railway vehicle coupled with a curved track is investigated in detail with a numerical method when a wheelset is steadily curving. In the calculation of rail corrugation we consider the combination of Kalker‘s rolling contact theory modified, a model of material loss on rail running surface, and a dynamics model of railway vehicle coupled with a curved track. In the establishment of the dynamic model, for simplicity, one fourth of the freight car without lateral motions,namely a wheelset and the equivalent one fourth freight car body above it, is considered. The Euler beam is used to model the rails and the track structure under the rails is replaced with equivalent springs, dampers and mass bodies. The numerical results show the great influence of the rail corrugation on the vibration of the parts of the vehicle and the track, and the some characters of rail corrugation in development.     

Dynamic Stability and Random Vibrations of Rigid and Elastic Wheelsets

A stability analysis and vibration studies are presented for a passenger coach model which is equipped with rigid or elastic wheels. The elastic components between wheel rim and disc act as third suspension reducing the unsprung mass and isolating the passenger coach from the high frequency motion of the wheel rim. The vertical and lateral motion by such a design requires a thorough analysis of the system dynamics. The excitation of the vertical vibrations by stochastic track irregularities results in acceleration amplitudes of the carbody that may generate droning noise. A parameter study of spring and damper coefficients of the system with radialelastic wheels leads to considerably reduced droning noise and lower force level between wheel and rail. Furthermore, the eigenmotion of a rigid and an elastic wheelset rolling on a track, the so-called hunting, is investigated. The variation of the spring and damper coefficients shows limits to guarantee the stability of the system.