A Novel Model for Describing Rail Weld Irregularities and Predicting Wheel-Rail Forces Using a Machine Learning Approach

Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.

Effects of Lateral Motion on the Creep Forces in Wheel/Rail Rolling Contact

The influences of the lateral motion of a single wheelset running on a tangent railway on the creepages and creep forces between wheel and rail are investigated with numerical methods. The effect of the yaw motion of wheelset is neglected in the analysis, and Kalker’s theory of three dimensional elastic bodies in rolling contact is employed to analyze the creep forces in the wheel/rail rolling contact with Non Hertzian form.

Influence of Angle of Attack and Lateral Force between Wheel and Rail on Wear of Rail ——a Laboratory Study

Angle of attack and lateral force are two important parameters influencing wheel rail wear. This paper deals with the question of influences of the angle of attack and the lateral force on the wear of rail. A series of experiments are conducted on 1/4 JD 1 Wheel/Rail Tribology Simulation Facility. The angles of attack selected in the tests are 0°16′30″, 0°37′40″ and 1°0′0″ respectively. The lateral forces selected in the tests are 0.694 kN, 1.250 kN and 2.083 kN, respectively corresponding to the lateral forces of 25 kN, 45 kN and 75 kN measured in the field, with the aim of keeping the same ratio of L/V between laboratory and field conditions. It is found that the larger the angle of attack is, the more serious the wear of rail is. The relation of rail wear rate versus angle of attack is non linear, and the relation of rail wear rate versus lateral force is approximately linear. The influence of angle of attack is more serious than that of lateral force. For the tractive wheelset, the wear index involving linear and quadratic function terms of angle of attack has good agreement with the limited experimental data. Some conclusions are given.

Study on the Curve of Lateral Creep Force of Wheel and Rail

Through the establishment of the negotiation model ofa single-wheelset, the changed curve of the wheel-rail lateral contact characteristic under different working conditions of track media was simulated and analyzed.The elastic mode of the wheel pair, the transverse elasticity of the track, the stick-slip vibration between the wheel and the track, the negative gradient characteristic of the actual creep force characteristic curve, and the right shift characteristic of the saturation point are considered by Simulink model.This can explain many kinds of creep theory and engineering phenomena and also can provide the support of the theoretical and practical for further research based on creep characteristic curve.

Safety evaluation for railway vehicles using an improved indirect measurement method of wheel–rail forces

The wheel-rail force measurement is of great importance to the condition monitoring and safety evaluation of railway vehicles. In this paper, an improved indirect method for wheel-rail force measurement is proposed to evaluate the running safety of railway vehicles. In this method, the equilibrium equations of a suspended wheelset are derived and the wheel-rail forces are then be obtained from measured suspension and inertia forces. This indirect method avoids structural modifications to the wheelset and is applicable to the long-term operation of railway vehicles. As the wheel-rail lateral forces at two sides of the wheelset are difficult to separate, a new derailment criterion by combined use of wheelset derailment coefficient and wheel unloading ratio is proposed. To illustrate its effectiveness, the indirect method is applied to safety evaluation of rail- way vehicles in different scenarios, such as the cross wind safety of a high-speed train and the safety of a metro vehicle with hunting motions. Then, the feasibility of using this method to identify wheel-rail forces for low-floor light rail vehicles with resilient wheels is discussed. The values identified by this method is compared with that by Simpack simulation for the same low-floor vehicle, which shows a good coincidence between them in the time domain of the wheelset lateral force and the wheel-rail vertical force. In addition, use of the method to determine the high-frequency wheel-rail interaction forces reveals that it is possible to identify the high-frequency wheel-rail forces through the accelerations on the axle box.

An integrated approach for the optimization of wheel-rail contact force measurement systems

A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.

Wheel/rail-force–based maintenance interval extension of the C80 series wagon

Purpose–This study aims to introduce the achievements and benefits of applying wheel/rail-force–based maintenance interval extension of the C80 series wagon in China.Design/methodology/approach–Chinese wagons’existing maintenance strategy had left a certain safety margin for the characteristics of widely running range,unstable service environment and submission to transportation organization requirements.To reduce maintenance costs,China railway(CR)has attempted to extend the maintenance interval since 2020.The maintenance cycle of C80 series heavy haul wagons is extended by three months(no stable routing)or 50,000 km(regular routing).However,in the meantime,the alarming rate of the running state,a key index to reflect the severe degree of hunting stability,by the train performance detection system(TPDS)for the C80 series heavy haul wagons has increased significantly.Findings–The present paper addresses a big data statistical way to evaluate the risk of allowing the C80 series heavy haul wagons to remain in operation longer than stipulated by the maintenance interval initial set.Through the maintenance and wayside-detectordata,whichis divided intothreestages,the extension period(three months),the current maintenance period and the previous maintenance period,this method reveals the alarming rate of hunting was correlated with maintenance interval.The maintainability of wagons will be achieved by utilizing wagon performance degradation modeling with the state of the wheelset and the often-contact side bearing.This paper also proposes a statistical model to return to the average safety level of the previous maintenance period’s baseline through correct alarming thresholds for unplanned corrective maintenance.Originality/value–The paper proposes an approach to reduce safety risk due to maintenance interval extension by effective maintenance program.The results are expected to help the railway company make the optimal solution to balance safety and the economy.

Modeling of Energy Processes in Wheel-Rail Contacts Operating under Influence of Periodic Discontinuous Forces

In this paper we present new numerical simulation approaches for determining the energy processes under periodic conditions caused by time-discontinuous forces in the wheel-rail contacts. The main advantage of the presented method is the total elimination of frequency analysis, which in effect introduces important simplifications in the identification of the effects in the contact. The second important feature is the fact that the method is based on the analysis of appropriate loops on the energy phase plane leading to an easy estimation of the rail strength through the evaluation of the loop’s area. That model based simulation in the applied dynamics relies on advanced methods for model setup, robust and efficient numerical solution techniques and powerful simulation tools for practical applications. Fundamental properties of contact displacements of the rail surface have been considered on the basis of the newly established method. The contact zone between railway wheels and the rail surfaces made of bulk materials is perceived as strong enough to resist the normal (vertical) forces introduced by heavy loads and the dynamic response induced by track and wheel irregularities. The analysis is carried out for a wheel running on an elastic rail rested on sleepers arranged on completely rigid foundation. The equations of displacement motion are established through the application of the Lagrange equations approach. The established model of the wheel-rail contact dynamics has been applied to that same roll plane but with taking into account a nonlinear characteristic of the sleeper with respect to the ground. Attention then is focused completely on the modeling of the energy absorbed by the rail. The applied method employs the energy state variables as time functions leading to determine the susceptibility of a given contact on the strength induced by the rail roll.

Experimental study of the wheel/rail impact caused by wheel flat within 400 km/h using full-scale roller rig

Purpose–In service,the periodic clashes of wheel flat against the rail result in large wheel/rail impact force and high-frequency vibration,leading to severe damage on the wheelset,rail and track structure.This study aims to analyze characteristics and dynamic impact law of wheel and rail caused by wheel flat of high-speed trains.Design/methodology/approach–A full-scale high-speed wheel/rail interface test rig was used for the test of the dynamic impact of wheel/rail caused by wheel flat of high-speed train.With wheel flats of different lengths,widths and depths manually set around the rolling circle of the wheel tread,and wheel/rail dynamic impact tests to the flats in the speed range of 0–400 km/h on the rig were conducted.Findings–As the speed goes up,the flat induced the maximum of the wheel/rail dynamic impact force increases rapidly before it reaches its limit at the speed of around 35 km/h.It then goes down gradually as the speed continues to grow.The impact of flat wheel on rail leads to 100–500 Hz middle-frequency vibration,and around 2,000 Hz and 6,000 Hz high-frequency vibration.In case of any wheel flat found during operation,the train speed shall be controlled according to the status of the flat and avoid the running speed of 20 km/h–80 km/h as much as possible.Originality/value–The research can provide a new method to obtain the dynamic impact of wheel/rail caused by wheel flat by a full-scale high-speed wheel/rail interface test rig.The relations among the flat size,the running speed and the dynamic impact are hopefully of reference to the building of speed limits for HSR wheel flat of different degrees.

Multi-Body Dynamics Modeling of Heavy Goods Vehicle-Rail Interaction

Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonableness of the line-coupled dynamics model is verified by using the maximum residual acceleration, the nonlinear critical speed of the wagon. The experimental results show that the established vehicle line coupling dynamics model meets the requirements of vehicle line coupling dynamics modeling.

关键参数对缓圆点波磨区段轮轨力的影响分析

以探究重载线路运行参数对车辆通过缓和曲线低轨侧波磨区轮轨力的影响规律为目的,基于Simpack多体动力学软件搭建了C80车辆-轨道耦合多体动力学模型,利用Matlab生成美国五级轨道随机不平顺,叠加缓圆点前钢轨波磨时域激励作为模型输入,仿真得到在缓圆点处不同波长、波深波磨状态下,缓和曲线长度、曲线半径、超高、行驶速度等关键参数对轮轨力的影响。通过分析一位轮对的轮轨力变化趋势和其最大增长率,发现波磨侧的轮轨力受波磨影响较大;无波磨一侧轮轨横向力受波磨的影响比垂向力大;曲线参数中,各指标最大增长率均随速度的增加而下降;除高轨侧轮轨横向力外,其余指标均随曲线半径的增大而减小;缓和曲线长度和超高的变化,对各指标最大增长率没有明显的降低作用,甚至随着运行参数的增加,指标最大增长率反而增加。

考虑车轮多边形磨损的机车轮轨动力特性研究

针对车轮的多边形磨损,建立了重载列车轨道三维耦合动力学模型,研究了机车车轮多边形磨损引起的轮轨动力相互作用。在动力学模型中嵌入了低粘着区(LAZ)和防滑控制算法,以分析在正常和低粘着条件下车轮多边形磨损对轮轨纵向和横向相互作用的影响。在两台不同磨损模式的机车上进行了对比试验,包括车轮周向磨损测量和机车振动试验,验证了模型的合理性。在此基础上分析了多边形磨损的动态响应,结果表明车轮多边形磨损不仅会加剧车轮/轨道的垂直力,还会加剧车轮与轨道之间的纵向相互作用。多边形磨损对机车前两轮对与后两轮对的纵向相互作用影响较大。

高速列车偏心车轮踏面的高阶多边形磨耗机理研究

目的研究高铁车轮几何偏心与车轮踏面高阶多边形磨耗之间的关系。方法在匀速运行期间对高速列车轴箱体的三向振动加速度进行测试,并分析功率谱密度;建立轮对-钢轨系统有限元模型,采用瞬时动态法计算车轮不同几何偏心工况下轮轨力的波动情况;采用复特征值法分析轮轨在饱和纵向蠕滑力激励下系统的稳定性,预测引起车轮高阶多边形磨耗的轮轨不稳定振动,并研究对列车运行速度和运营环境的影响。结果高速列车以237 km/h的速度运行且轮轨摩擦因数为0.23时,0.7 mm及以上的车轮几何偏心量会导致轮轨最大纵向蠕滑力达到饱和状态,引起614 Hz的轮轨系统不稳定振动,造成车轮24~25阶多边形磨耗的形成。当车速从200 km/h分别增至300、400 km/h时,引起纵向蠕滑力饱和的车轮几何偏心临界值从0.8 mm分别减至约0.67、0.56 mm。当轮轨间摩擦因数为0.21及以上时,饱和纵向蠕滑力激励的轮轨系统614 Hz不稳定振动的等效阻尼比随着轮轨摩擦因数的增大而减小。在摩擦因数0.21~0.27范围内,该振动的发生趋势线性增强。当摩擦因数降至0.21以下时,该振动趋于稳定。结论在列车高速运行时,超过一定临界值的车轮几何偏心可引起轮轨纵向蠕滑力周期性饱和,激发轮轨系统不稳定振动,从而引起踏面高阶多边形磨耗。车速的提高会导致车轮几何偏心临界值的降低,轮轨摩擦因数增大会造成不稳定振动的发生趋势线性增强,进而引发更为严重的车轮高阶多边形磨耗。

基于GPD理论和百分位数阈值法的轮轨力极值估计与动力系数研究

在高速铁路无砟轨道结构设计和检算时,列车荷载设计值是关键的设计参数之一。基于GPD理论,研究全波段不平顺激励下的轮轨力极值估计方法,并与脉冲激励下的结果对比,为无砟轨道结构设计和相关规范的完善提供依据。结果表明:采用百分位数法选取阈值时,应对样本分簇以提高样本之间的独立性和轮轨力极值估计的精度;提出结合百分位数阈值的形状参数筛选法进行轮轨力极值估计,确定了每簇样本量大小和形状参数区间;样本量宜取3×10^(5)~5×10^(5)个,百分位数阈值宜取50%~98%,且以轮轨力极值估计值的均值作为最终的轮轨力极值估计值;列车速度为250~400 km/h的列车荷载设计值动力系数分别为2.2、2.4、2.6和2.8。

轨道车辆垂向轮轨力时域识别对比及其机器学习修正

为了尽可能减小轨道车辆垂向轮轨力时域识别中存在的误差,以时域法为基础,开展了基于机器学习修正的轨道车辆垂向轮轨力识别研究.首先建立了车辆动力学仿真模型,获取了车辆在随机轨道激励下以250km/h速度行驶时的轴箱加速度响应和垂向轮轨力.其次,建立了Green函数法、状态空间法这2种时域法对应的动载荷识别模型,对状态空间法的初值误差进行了分析,并引入多项式拟合法修正其趋势项误差,进而对比分析了2种方法的计算精度和计算效率.然后,针对时域法存在的识别误差,提出采用NARX(nonlinear autoregressive models with exogenous inputs)模型对识别误差进行训练和预测,用于消减模型中存在的如响应观测不全与观测噪声等因素造成的影响,进而对时域法识别结果进行修正,提高识别精度.最后,通过一个10自由度轨道车辆垂向动力学模型,对方法的正确性进行了验证.研究结果表明:2种方法对轨道车辆垂向轮轨力均具有较高的识别精度,对于各轮对的识别精度各有优劣;在计算效率方面,状态空间法比Green函数法更优;经NARX模型修正的2种时域法对轨道车辆垂向轮轨力均具有很好的识别效果,识别值与正演值的Pearson相关系数大于0.99,为极强相关.基于NARX模型的机器学习误差修正方法可有效提高时域识别精度,可以为后续轨道车辆轮轨力预测提供参考,具有较强的工程运用价值.

小半径曲线上P75钢轨打磨廓形设计及应用研究

以国内某重载铁路R400 m曲线P75钢轨为研究对象,建立了轮轨接触模型和轮径差曲线描述模型,选取代表性车轮踏面和钢轨廓形,采用轮径差曲线逆向求解法优化了轮轨接触区域钢轨廓形,并依据打磨量最小化原则设计得到了曲线钢轨打磨廓形。建立了实测参数下的车辆-轨道多体动力学仿真模型,对比分析了实测廓形和设计廓形匹配下的动力学指标。按钢轨廓形设计要求,在该R400 m曲线上实施了钢轨打磨试验和轮轨动力学测试。研究结果表明,优化后轮径差曲线趋于平滑,车辆曲线通过能力得到提高,抗脱轨能力得到保持;轮轨关系得到显著改善、轮轨接触点交叉跳跃和集中问题得到缓解;轮轨横向力减小20%以上,脱轨系数减小16%以上,钢轨法向接触应力减小32%以上,轮轨蠕滑力减小26%以上;实施打磨后,轮轨横向力减小34%以上,脱轨系数减小35%以上,钢轨振动加速度减小35%以上;打磨后3个月轨面疲劳伤损未见明显发展,钢轨使用寿命由前一换轨周期的8个月延长至13.5个月。仿真分析和打磨试验验证了钢轨廓形设计方法在重载铁路小半径曲线的应用效果。

轮轨接触点位置变化对测力轮对测量影响及其补偿方法

[目的]列车运行过程中,轮对存在随机振动,导致轮轨接触点位置发生变化,进而影响轮轨力的测量结果。为了解决该问题,提出一种测量补偿方法。[方法]介绍了轮轨接触点位置变化对测力轮的影响;介绍了轮轨接触点位置变化后,轮轨力测量的补偿方案;通过仿真分析,验证考虑轮轨接触点位置变化的轮轨力测量补偿方案的有效性。[结果及结论]添加美国五级轨道不平顺谱激励后,轮轨接触点位置最大偏移量为17.53 mm,垂向力最大相对误差达到了22.85%;采用所提测量补偿方法后,轮轨垂向力最大相对误差为8.02%,测量精度明显提高。叠加尖弯不平顺谱后,脱轨系数最大达到了1.016 8,超过允许限度;采用无偏移标定系数计算出的脱轨系数为0.347 7,采用所提补偿方法计算出的脱轨系数为0.962 2,说明该方法能够更准确地反映出列车的运行安全状态。

基于轮轨力测量的新型轨道交通轮对智能运维监测系统研制

轮轨力直接反映了列车-线路耦合状态及车轮服役损伤水平,创新发展轮轨力在线测量技术对保障列车运行安全至关重要。简述了现有直接轮轨力测量系统的工作原理及存在的不足,通过传感器结构设计、数据融合算法及软件处理系统开发,研制了一种新型轨道交通轮对智能运维监测系统(RIM)。基于剪力法轮轨力测量原理,利用设计研发的钢轨卡装式H型剪力传感器组桥阵列及多通道信号重构技术实现了轮轨力的连续测量。同时,通过制定系统测区布置方案,提出各检测功能评价方法,并构建监测系统网络架构,能满足对车轮踏面损伤、车辆偏载及超员检测等功能需求。经某地铁公司现场实测验证,本系统无需对轨道结构进行任何改动,拆装方便快捷,并能连续重叠采集测量区间内的轮轨力信号,有效弥补了单个剪力测量点独立工作产生的测量盲区,实现了轮轨垂向力的米级连续在线测量。

城市轨道交通列车轮轨垂向力测量方法

[目的]城市轨道交通运营中通常会出现大量的隧道病害,列车轮轨力是各种病害的主要成因,因此,需在不影响城市轨道交通列车正常运营的条件下,对列车轮轨垂向力的测量方法进行研究。[方法]以成都地铁7号线茶店子站—一品天下站下行区间道床剥离病害为研究对象,基于弯矩差法理论,采用ANSYS有限元软件建立了静荷载及动荷载作用下的钢轨有限元模型,并对其进行了数值模拟分析。在室内对1根长2 m、3跨布置的钢轨进行了标定试验。[结果及结论]静荷载数值模拟分析表明,钢轨测点可选择在钢轨跨中轨底上表面边缘两侧位置;当钢轨跨中位置受到垂向力作用时,该点沿钢轨方向的应变最大,且应变随垂向力线性增加。通过标定试验测得的标定系数为0.6260×10^(6)kN,而数值模拟测得的标定系数为0.6441×10^(6)kN,两者偏差仅2.8%,可通过静荷载标定试验确定标定系数。轮轨垂向力的测量方法可以更好地评估轨道结构和列车运行的安全性,及时发现安全隐患,并采取相应措施进行修复和改进。

城市轨道交通轮轨力间接测量法仿真验证

针对现有传统轮轨力直接测量法测力轮对安装复杂、前期贴片与标定操作难度较大且成本较高等问题,以现有的相关研究为基础,以城市轨道交通列车为研究对象,利用Simpack动力学软件对轮轨力间接测量法进行仿真验证。推导出轮轨力间测量法的理论公式,利用Simpack软件,建立车辆-轨道动力学仿真模型,通过运算得出直线段轮轴横向力与轮轨垂向力两者在不同工况下误差的50%、75%、90%与最大值。结果表明,间接测量法具有较高的测量精度,为城市轨道交通轮轨力测量提供可选方案。