轨底坡对轮轨滚动接触行为的影响

为了探讨轨底坡与轮轨滚动接触行为的内在联系,针对高速客运专线轮轨接触状况,即轮对踏面为LMA和钢轨为国产CN60,利用改进的三维接触几何程序、Kalker的三维弹性体非赫兹滚动接触理论及其CONTACT数值程序,分析比较轨底坡对轮轨接触几何参数、接触斑形状、接触斑滑动量、摩擦功、接触应力等的影响.通过分析计算可得,轨底坡对轮轨滚动接触行为有很大影响.尤其当轮对相对轨道横移在6 mm～9 mm范围内变化时,随着轨底坡从1/20到1/40的逐渐减小,轮对左右轮滚动半径差和等效锥度增大,这说明在1/40轨底坡下,轮对恢复对中的能力更好,更有利于曲线通过.1/40轨底坡对应的最大正压力、等效应力等较小,其对应的摩擦功较大.1/20轨底坡的情况刚好相反.综合考虑各种因素,对于LMA-CN60轮轨接触副,1/40轨底坡较1/20轨底坡的接触状态更好.数值结果为轨底坡的设计提供重要的参考依据.     

钢轨轨底坡对LM和LMA两种轮对接触行为的影响

为揭示轨底坡与两种踏面的轮轨滚动接触行为之间内在联系,利用改进数值算法分析不同轨底坡下,LM踏面和LMA踏面车轮沿中国钢轨60 kg/m (CHN60)上滚动接触时的接触几何参数、轮轨接触点处的刚性蠕滑率的变化情况,再根据Kalker的三维弹性体非赫兹滚动接触理论,详细地分析两种轮对滚动接触斑上的正压力和切向力分布.利用弹性力学中Bossinesq-Cerruti力/位移计算公式并借助Gauss数值积分方法,确定两种型面轮轨滚动接触时体内的弹性位移、应变和应力的分布情况.分析计算中,考虑两种车轮半径420 mm和460 mm.计算结果表明,1/20轨底坡下LM踏面车轮对应的接触应力等参量远小于1/40轨底坡下的情况,LMA踏面轮对的情况刚好相反.由此可知,对于LM-CHN60轮轨接触副,1/20轨底坡较1/40的好;对于LMA-CHN60轮轨接触副,1/40轨底坡较1/20的好.车轮半径对LM-CHN60和LMA-CHN60的滚动接触行为的影响不大.数据结果为轮轨型面优化设计和轨底坡的设计提供了重要的参考依据.     

车轮型面对轮轨滚动接触行为影响及选用

分析两种轨底坡情况下锥形踏面与磨耗型踏面车轮的滚动接触行为,结合钢轨损伤行为提出车轮型面的选用要求.结果表明,轨底坡从1∶40变为1∶20时,磨耗型和锥形踏面的滚动接触几何参数将发生很大的变化;轨底坡为1∶20时,磨耗型踏面的最大切应力和等效应力明显小于锥形踏面.磨耗型车轮踏面能减轻重载钢轨侧磨且等效锥度大于锥形踏面车轮;由于重载与高速铁路钢轨损伤形式的不同,建议优化设计高速铁路车轮踏面形状,以减轻高速钢轨疲劳损伤的发生.     

曲线半径及轴重对轮轨摩擦功影响的研究

基于非Hertz滚动接触理论利用数值计算方法详细分析了静态接触情况下,轴重和曲线半径对轮轨接触质点间等效应力、接触斑粘滑区的分布、总滑动量和摩擦功的影响。分析计算表明,轴重增加引起轮轨接触质点间等效应力,接触质点间粘滑区的面积以及总滑动量的变化,同时对轮轨接触质点阍的摩擦功的变化有重要影响;小曲线半径处轮轨接触质点间的总滑动量,接触斑滑移区的面积以及摩擦功都明显增大,导致曲线上钢轨磨损加剧。因此曲线半径和轴重是影响轮轨滚动接触磨损的重要因素。     

基于轮轨型面匹配数值模拟的地铁车轮异常磨耗原因分析

通过线路测试和数值仿真对某B型地铁列车车轮异常磨耗现象进行深入分析。结合轮轨接触几何关系和轮轨滚动接触理论进行轮轨静态接触分析;基于UM软件建立该地铁车辆动力学仿真模型和磨耗预测模型,计算轮对运动状态和车轮磨耗水平。通过对比不同轮轨匹配的仿真结果来分析该地铁车辆发生轮缘和踏面异常磨耗的原因,进而提出相应的控制措施。结果表明,该地铁线路小半径曲线占比较大且钢轨轨底坡异常。地铁车辆轮缘和踏面异常磨耗是由较大轨底坡线路条件下轮轨型面匹配关系不合理所导致。将全线轨底坡修正成1/40对车轮异常磨耗现象的减缓效果有限。为有效减轻该地铁车辆车轮异常磨耗,可考虑将车轮踏面外形由S1002镟修为LM。     

横移量、摇头角对轮轨滚动接触行为的影响研究

基于非Hertz滚动接触理论利用数值计算方法详细分析了静态接触情况下,横移量和摇头角对轮轨接触质点间蠕滑力、接触斑粘滑区的分布、等效应力的影响.通过数值计算表明:横移量、摇头角的变化对轮轨滚动接触行为的影响是同时存在并且相互影响的.随着横移量的增加,接触斑的滑动区逐渐增大,粘着区面积逐渐减小,横向移动分量逐渐增大,最大应力值逐渐减小;随着摇头角的增大,接触斑上滑移区面积和最大剪应力和等效应力值均逐渐增大,直至接触斑处于全滑动状态,当轮轨接触斑上的切向力达到饱和时,摇头角对接轮轨接触斑上的蠕滑力、粘滑区分布和应力分布没有影响,计算结果对研究轮轨滚动接触疲劳提供一定的参考价值.     

轮轨直线滚动过程接触力学性能计算方法

以铁路客运列车直线运行时的轮轨接触问题为研究对象,在利用前期研究构建的薄层模型计算轮轨非赫兹接触正应力分布的基础上,分析了直线滚动时轮轨接触斑的蠕滑问题和切应力分布,进一步构建了精确求解任意形状接触斑正压力和切向力共同作用下轮轨内部各点应力的计算模型.结合算例,计算了不同类型轮轨接触斑内的滚动接触应力,并深入计算了钢轨内部各点的Mises应力和最大切应力,分析了滚动过程中接触斑上正压力和切向力对钢轨内部应力的影响规律.     

曲线几何参数对车辆轮轨磨耗的影响

运用SIMPACK动力学软件,从曲线段线路设计出发,对曲线轨道上曲线半径、曲线超高及轨底坡对轮轨磨耗的影响进行仿真计算和分析。结果表明:为降低轮轨磨耗及保证行车安全,应尽量减少小半径曲线;在规定范围内调整曲线超高可有效降低轮轨磨耗,但调整的过高或过低反而会增大磨耗;适当调整轨底坡可起到降低轮轨磨耗的作用,但效果不是太明显,且过大的轨底坡会加剧轮轨的磨耗。     

轮轨配合对重载货车轮轨磨耗的影响*

在中国既有线路的参数设置下,建立标准LM车轮与R60轨和R75轨配合时的轮轨接触和磨耗模型,对比研究不同轮轨配合时的磨耗性能。计算表明R75轨轮轨接触点集中分布在轨侧、轨头和轨顶三个区域,接触线不连续。在当轮对横移小于3 mm时,两种钢轨滚动圆半径差和接触角差基本一致,轮对横移大于3 mm时,R75轨的滚动圆半径差和接触角差稍小。R75轨与LM车轮配合时,在车轮踏面和轮缘、钢轨轨顶和轨角两段圆弧的过渡段的接触斑面积和应力变化剧烈。车辆在直线上运行时,R75轨的轮轨磨耗将增大数倍,动态通过800 m半径曲线时,外轨磨耗增大约45%。轮轨配合的理论分析表明R75轨不适应我国重载运输,采用提高强度的R60轨更符合我国重载铁路的实际情况。     

考虑摩擦因数与滑动速度相关时的轮轨滚动接触有限元分析

使用与滑动速度相关的摩擦因数替代库伦摩擦定律中的常系数,结合mixed Lagrangian/Eulerian方法建立轮轨滚动接触有限元模型,分析牵引力主导的蠕滑工况下的干燥状态的轮轨滚动接触特性。通过与摩擦因数取值为常数的轮轨滚动接触分析结果对比发现:与滑动速度相关的摩擦因数对轮轨滚动接触最大接触应力和接触斑面积影响不大,均在1%以内;但是对轮轨接触斑内最大Mises应力、最大纵向切应力、最大横向切应力和最大等效塑性应变影响较大,特别是对最大纵向切应力影响幅度近20%;更需要引起注意的是对轮轨滚动接触摩擦力矢量分布和切向塑性应变分布影响明显,这对轮轨滚动接触疲劳损伤分析非常重要。     

An investigation into the effect of train curving on wear and contact stresses of wheel and rail

Some important papers concerning the studies on rail wear and wheel/rail contact stresses are briefly reviewed. The present paper utilizes a numerical method to analyze the effect of railway vehicle curving on the wear and contact stresses of wheel/rail. The numerical method considers a combination of Kalker's non-Hertzian rolling contact theory, a material wear model and a vertical and lateral coupling dynamics model of the vehicle/track. In the analysis, the important factors influencing on the wear and the contact stresses are, respectively, the curving speed, the curved track super-elevation and the rail cant. Compared to the present model, some concerned models and results in the published papers are in detail discussed. Through the detailed numerical analysis, it is found that the difference between the normal loads of the left and right of the wheelset increases linearly with increasing the vehicle curving speed. The material wear volume per length along the rail running surface has a tendency to grow. However, the variation of the maximum normal contact stress has a large fluctuation as the curving speed increases. The increase of the maximum contact stress depends greatly on not only the normal load but also the profiles of the wheel/rail. Increasing the track super elevation efficiently lowers the normal load difference of the left and right of the front wheelset, and the contact stresses and the wear. The rail cant has a great influence on the low rail wear of the curve track. An increase in rail cant results in a great increase in the low rail wear of the curved track, and a decrease in the outside rail wear. These conclusions are very useful in the maintenance of the track.     

车轮滚动接触疲劳与磨耗耦合关系数值模拟

滚动接触疲劳和磨耗是车轮失效的主要方式。通过三维弹性体非赫兹滚动接触理论得到接触斑内的法向、切向应力和材料上不同深度处的最大切应力分布,以CL60钢和贝氏体车轮钢为例,基于"layer"滚动接触疲劳失效模型和Zobory车轮磨耗模型,分析LM型车轮踏面和75 kg.m–1钢轨型面匹配时轮轨接触条件和车轮材质对车轮滚动接触疲劳和磨耗竞争关系的影响。计算结果表明,摩擦因数为0.3时,CL60钢在小蠕滑条件下会发生滚动接触疲劳损伤,在大蠕滑条件下只有轴重大于30 t时才会出现滚动接触疲劳损伤,而贝氏体车轮钢只有在大蠕滑条件且轴重为30 t时,载荷循环次数小于1×105的情况下才会出现滚动接触疲劳损伤;摩擦因数为0.6时,CL60钢和贝氏体车轮钢在各种工况下的滚动接触疲劳损伤速度都小于相同条件下的磨耗速度。     

Decarburisation and rolling contact fatigue of a rail steel

Decarburisation is present on all new rails and unless ground off, will be on the running surface once installed. This paper presents a detailed investigation into the effect of decarburisation of rolling contact fatigue and wear. Twin disc testing has been used to study the phenomenon under water-lubricated rolling/sliding contact. Rail discs have been cut from grade 220 rail and heat-treated to give samples with varying depths of decarburisation. It was found that as the depth of decarburisation increased the wear rate of the rail disc increased while that of the wheel disc decreased. The effect of decarburisation on rolling contact fatigue was to increase the crack growth rate of samples with increasing depth. Cracks under rolling contact fatigue were propagated by contact stresses via the fluid pressure mechanism and influenced by microstructure. The effect of decarburisation was predicted to have little effect on rail/wheel contact when scaled from the laboratory tests using the depth of maximum shear stress.     

车速变化对钢轨磨损影响的数值计算与实验研究

用数值计算方法分析静态接触情况下,轮轨接触质点间蠕滑力、黏滑区的分布随横移量和摇头角变化速率的变化,利用模拟试验研究有制动力作用下车速对钢轨试样磨损特性的影响。结果表明:有制动力影响时钢轨磨损量随车速的增大呈非线性减小,在车速小于160 km/h时,钢轨磨损量随车速增加急剧减小,但是当车速超过200 km/h之后,磨损量随车速的增大而下降的趋势相对比较平缓;随着摇头角变化速率和横移量变化速率的增大,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。     

车轮磨耗计算模型及其数值方法

综述国内外车轮磨耗理论模型及其数值方法,提出基于车辆轨道垂、横向耦合动力学、轮轨滚动接触力学和材料摩擦磨耗模型为一体的车轮磨损计算模型, 并发展相应的数值方法。模型中车辆结构和钢轨下部结构被简化成等效质量、弹簧和阻尼系统, 而钢轨用Euler 梁代替, 并考虑它的垂向、横向弯曲变形和扭转变形。利用修改的KALKER三维弹性体非Hertz 滚动接触理论和相应的数值方法计算轮轨蠕滑力和滑动量等参量;根据Archard材料磨损模型计算车轮的磨耗深度。利用该模型和相应的数值方法分析不同曲线半径情况下车轮的磨损情况,结果表明该模型可以较好地模拟车轮磨损的演化过程。给出列车通过曲线半径为350 m时车轮的磨损情况。数值结果表明,每个转向架下前轮对比后轮对磨耗严重,外轨上的车轮比内轨上的车轮磨耗严重。     

ELASTIC-PLASTIC FINITE ELEMENT ANALYSIS OF THREE-DIMENSIONAL CONTACT-IMPACT AT RAIL JOINT

Using the finite element code ANSYS/LS-DYNA, a dynamic finite element model with anelastic-linear-kinematic-hardening plastic material is established to analyze elastic-plastic stresses inthe railhead in the impact process of wheel and rail occurring at the gap of rail joint. The model isbased on the discrete elastic support condition of the rails, which is suitable for the actual situation ofwheel/track rolling contact. In the analysis the influences of axle load, yield stress and tangent modulus     

Effect of small harmonic oscillations during the steady rolling of a cylinder on a plane

If a wheel rolling over a rail transmits a tangential traction, frictional microslip occurs in part of the contact area, resulting in energy dissipation and localized wear. If the applied forces oscillate in time, the resulting wear will be non-uniform, resulting in ‘corrugations’ that can grow with progressive passes, depending on the dynamics of the overall system. In this paper, a linear perturbation method is used to obtain closed-form expressions for the receptance of a two-dimensional rolling contact subjected to small oscillations in normal force and rotational speed superposed on a mean value in the limit of large coefficient of friction. Corresponding expressions are also obtained for the amplitude and phase of the energy dissipation in the contact, which is expected to correlate with the local wear rate.The results are compared with a simpler Winkler model of the contact and with other models that have been used for the analysis of rail corrugation. Surprisingly good agreement is obtained with numerical results due to Gross-Thebing for the receptances due to oscillations in rotational speed.     

EFFECT OF DISCRETE SUPPORTS OF RAIL ON INITIATION AND EVOLUTION OF RAIL CORRUGATION

The effect of discrete support of rail on the formation and evolution of rail corrugation is primarily investigated with numerical method in the situation of wheelset curving steadily and repeatedly. In the numerical analysis of corrugation it is considered that a combination of Kalker's rolling contact theory with non-Hertzian to be modified, a linear frictional work model and a vertical dynamics model of railway vehicle coupled with a curved track. And the uneven support stiffness of rail in the vertical direction due to discrete sleeper support and the different running speed of the wheelset are taken into consideration. The damage on the running surface of rail, concerning rail corrugation formation, is restricted to wear mechanism of rail material. The numerical results obtained indicate that the discrete supports of rail by sleepers have a great influence on the formation of the corrugation under the condition of non-zero and stable creepages of wheelset and track.