Influence of railway wheel tread damage on wheel-rail impact loads and the durability of wheelsets

Dynamic wheel-rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds.Based on laser scanning,the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle-track interaction to calibrate and verify a simulation model.The relation between the magnitude of the impact load and various operational parameters,such as vehicle speed,lateral position of wheel-rail contact,track stiffness and position of impact within a sleeper bay,is investigated.The calibrated model is later employed in simulations featuring other forms of tread damage;their effects on impact load and subsequent fatigue impact on bearings,wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed.The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear,and for general assessment of the severity of different types of railway wheel tread damage.

Influence of dynamic unbalance of wheelsets on the dynamic performance of high-speed cars

With further increasing in running speed of newer high-speed EMUs（electric multiple units）,higher demand for wheelset dynamic balance is required.In order to study the influence of the dynamic unbalance of wheelset on the stability,ride quality,and curving performance for a high-speed car,a detailed dynamic model of a high-speed EMU car is established using the software SIMPACK.The analysis results indicate that the dynamic unbalance of the wheelset significantly influences the dynamic performance of the high-speed car.The increase in dynamic unbalance of the wheelset will decrease the hunting critical speed,worsen the vertical ride quality,and increase the wheelset lateral force,derailment coefficient,and wheel unloading ratio.Therefore,in order to improve the stability,ride quality,and running safety of high-speed car,the values of dynamic unbalance of wheelset should be strictly controlled in manufacturing,and periodically monitored in operation.

Useful zero friction simulations for assessing MBS codes Pascal’s formula giving wheelsets frequency for zero wheel-rail friction

Present study provides a simple analytical formula,the“Klingel-like formula”or“Pascal’s Formula”that can be used as a reference to test some results of existing railway codes and specifically those using rigid contact.It develops properly the 3D Newton-Euler equations governing the 6 degrees of freedom(DoF)of unsuspended loaded wheelsets in case of zero wheel-rail friction and constant conicity.Thus,by solving numerically these equations,we got pendulum like harmonic oscillations of which the calculated angular frequency is used for assessing the accuracy of the proposed formula so that it can in turn be used as a fast practical target for testing multi-body system(MBS)railway codes.Due to the harmonic property of these pendulum-like oscillations,the squareω2 of their angular frequency can be made in the form of a ratio K/M where K depends on the wheelset geometry and load and M on its inertia.Information on K and M are useful to understand wheelsets behavior.The analytical formula is derived from the first order writing of full trigonometric Newton-Euler equations by setting zero elastic wheel-rail penetration and by assuming small displacements.Full trigonometric equations are numerically solved to assess that the formula providesω2 inside a 1%accuracy for usual wheelsets dimensions.By decreasing the conicity down to 1×10^(−4) rad,the relative formula accuracy is under 3×10^(−5).In order to test the formula reliability for rigid contact formulations,the stiffness of elastic contacts can be increased up to practical rigidity(Hertz stiffness×1000).

Research on the influence of flexible wheelset rotation effect on wheel rail contact force

Purpose-Under the high-speed operating conditions,the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition.In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction,it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approach-The wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper.As for the wheel-rail contact forces,which is a particular force element in vehicle multibody system,a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation.Based on the flexible wheelset modeling approach in this paper,two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established,two kinds of track excitations,namely normal measured track irregularities and short-wave irregularities are used,wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.Findings-Under normal track irregularity excitations,the amplitudes of vertical,longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model,and the virtual penetration and equivalent contact patch are also slightly smaller.For the flexible wheelset model,the wheel rail longitudinal and lateral creepages will also decrease.The higher the vehicle speed,the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model.Under track short-wave irregularity excitations,the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset.However,unlike the excitation case of measured track irregularity,under short-wave excitations,for the speed within the range of 200 to 350 km/h,the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase.This is partly due to the contribution of wheelset's elastic vibration under short-wave excitations.For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above,as well as high-frequency wheel-rail interaction analysis problems under various speed conditions,the flexible wheelset model will give results agrees better with the reality.Originality/value-This study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system.Furthermore,by comparative research,the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained,which is useful to the application scope of rigid and flexible wheelset models.

Analysis of steering performance of differential coupling wheelset

In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differential cou- pling wheelset （DCW） was developed in this work. The DCW was composed of two independently rotating wheels （IRWs） coupled by a clutch-type limited slip differential. The differential contains a static pre-stress clutch, which could lock both sides of IRWs of the DCW to ensure a good steering performance in curves with large radius and tangent track. In contrast, the clutch could unlock the two IRWs of the DCW in a sharp curve to endue it with the characteristic of an IRW, so that the vehicles can go through the tight curve smoothly. To study the dynamic performance of the DCW, a multi-body dynamic model of single bogie with DCWs was established. The self-centering capability, hunting stability, and self-steering performance on a curved track were analyzed and then compared with those of the conventional wheelset and IRW. Finally, the effect of coupling parameters of the DCW on the dynamic performance was investigated.

Effects of wheelset vibration on initiation and evolution of rail short-pitch corrugation

The initiation and evolution of short-pitch corrugation in Beijing metro line 4 was studied from the viewpoint of wheelset vibration.A three-dimensional elastic model was set up.Numerical simulations were undertaken with this model to analyze the corrugation by the wheelset vertical vibration and torsional vibration.Based on numerical results,the relation between rail corrugation and wheelset vibration,and the relation between the position of electromotor and wheelset vibration were indicated.It is found that avoiding the wheelset-rail resonance is one method of controlling the rail short-pitch corrugation and solving the vibration and noise problem in metro lines.

Effect of wheelset flexibility on wheel–rail contact behavior and a specific coupling of wheel–rail contact to flexible wheelset

The fexibility of a train＇s wheelset can have a large effect on vehicle–track dynamic responses in the medium to high frequency range.To investigate the effects of wheelset bending and axial deformation of the wheel web,a specifi coupling of wheel–rail contact with a fexible wheelset is presented and integrated into a conventional vehicle–track dynamic system model.Both conventional and the proposed dynamic system models are used to carry out numerical analyses on the effects of wheelset bending and axial deformation of the wheel web on wheel–rail rolling contact behaviors.Excitations with various irregularities and speeds were considered.The irregularities included measured track irregularity and harmonic irregularities with two different wavelengths.The speeds ranged from 200 to400km/h.The results show that the proposed model can characterize the effects of fexible wheelset deformation on the wheel–rail rolling contact behavior very well.

Research on hunting stability and bifurcation characteristics of nonlinear stochastic wheelset system

A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stochastic parametric excitations of equivalent conicity and suspension stiffness.The wheelset is systematized into a onedimensional(1D)diffusion process by using the stochastic average method,the behavior of the singular boundary is analyzed to determine the hunting stability condition of the wheelset system,and the critical speed of stochastic bifurcation is obtained.The stationary probability density and joint probability density are derived theoretically.Based on the topological structure change of the probability density function,the stochastic Hopf bifurcation form and bifurcation condition of the wheelset system are determined.The effects of stochastic factors on the hunting stability and bifurcation characteristics are analyzed,and the simulation results verify the correctness of the theoretical analysis.The results reveal that the boundary behavior of the diffusion process determines the hunting stability of the stochastic wheelset system,and the left boundary characteristic value cL=1 is the critical state of hunting stability.Besides,stochastic D-bifurcation and P-bifurcation will appear in the wheelset system,and the critical speeds of the two kinds of stochastic bifurcation decrease with the increase in the stochastic parametric excitation intensity.

FPGA Implementation of Extended Kalman Filter for Parameters Estimation of Railway Wheelset

It is necessary to know the status of adhesion conditions between wheel and rail for efficient accelerating and decelerating of railroad vehicle.The proper estimation of adhesion conditions and their real-time implementation is considered a challenge for scholars.In this paper,the development of simulation model of extended Kalman filter(EKF)in MATLAB/Simulink is presented to estimate various railway wheelset parameters in different contact conditions of track.Due to concurrent in nature,the Xilinx®System-on-Chip Zynq Field Programmable Gate Array(FPGA)device is chosen to check the onboard estimation ofwheel-rail interaction parameters by using the National Instruments(NI)myRIO®development board.The NImyRIO®development board is flexible to deal with nonlinearities,uncertain changes,and fastchanging dynamics in real-time occurring in wheel-rail contact conditions during vehicle operation.The simulated dataset of the railway nonlinear wheelsetmodel is tested on FPGA-based EKF with different track conditions and with accelerating and decelerating operations of the vehicle.The proposed model-based estimation of railway wheelset parameters is synthesized on FPGA and its simulation is carried out for functional verification on FPGA.The obtained simulation results are aligned with the simulation results obtained through MATLAB.To the best of our knowledge,this is the first time study that presents the implementation of a model-based estimation of railway wheelset parameters on FPGA and its functional verification.The functional behavior of the FPGA-based estimator shows that these results are the addition of current knowledge in the field of the railway.

Influence of unsupported sleepers on the dynamic stability of ballasted bed based on wheelset impact tests

The unsupported sleeper can change the load characteristics of ballast particles and thus affect the dynamic stability of a ballasted bed.In this work,a laboratory test was constructed on a ballasted track containing unsupported sleepers.The ballasted track was excited by a wheelset,and the influence of unsupported sleepers on the dynamic stability of a ballasted bed was studied.The results show that the main frequency of the sleeper vibration appeared at 670 Hz,and the first-order rigid vibration mode at the frequency of 101 Hz had a significant effect on the condition without the unsupported sleeper.When the sleepers were continuously unsupported,the vibration damping effect of ballasted bed within the frequency range of 0–450 Hz was better than that at higher frequencies.Within the frequency range of 70–250 Hz,the vibration damping effect of the ballasted bed with unsupported sleepers was better than that without the unsupported sleeper.Owing to the excitation from the wheelset impact,the lateral resistance of the ballasted bed with unsupported sleepers whose hanging heights were 30,60,and 90 mm increased by 37.43%,12.25%,and 18.23%,respectively,while the lateral resistance of the ballasted bed without the unsupported sleeper remained basically unchanged.The unsupported sleeper could increase the difference in the quality of the ballasted bed between two adjacent sleepers.In addition,test results show that the hanging height of the unsupported sleeper had little effect on the lateral resistance of a ballasted bed without external excitation,but had an obvious effect on the rate of change of the lateral resistance of a ballasted bed and the acceleration amplitude of the sleeper vibration under the wheelset impact.

A Nondestructive Instrumented Wheelset System for Contact Forces Measurements

A nondestructive continuous instrumented wheelset design is proposed based on strain gauges placing inside of the wheel web and wireless telemetry system. The signal feature analysis including frequency contents and high order harmonic ripples is also carried out. The strain gradient decoupling method for vertical and lateral force identification is proposed based on the strain distributions under respective loads. The method implements minimum crosstalk effects and insensitive to the varying contact points. The KMT telemetry system is adopted for wireless inductive powering and signal transferring. The drilling holes on the wheel and axles are avoidable to ensure the integrity and long-term using of the wheelset. Bridging and demodulating schemes for lateral and vertical force are designed respectively as they have dramatic differences at the dynamic signal features. High order harmonic ripple analysis and error estimation are gotten by independent waveforms. Based on the data form calibration test rig, it is indicated that the high order ripple amplitudes are below 10% of the demodulation amplitudes and fulfill designed requirements.

列车轮对简化模型重力刚度与滚动半径的计算方法

在建立列车轮对简化模型动力学方程中,如果假设侧移和摇头角是微小量,及质心高度保持不变,可以较简便地求出重力刚度和滚动半径等量的近似表达式。本文用几何方法给出了轮对质心高度和滚动半径与侧向位移之间的函数关系,从而可以获得这些量的解析表达式;另外还通过运动学方法,证明了重力刚度和滚动半径等量的简便计算方法是正确的。

采用弹性车轮的独立轮对有轨电车曲线通过动力学性能研究

采用动力学仿真软件SIMPACK,利用离散刚度阻尼单元模拟弹性车轮的弹性变形特性,建立了三编组现代有轨电车列车动力学计算模型,对比分析了曲线半径R400 m线路条件下弹性车轮在时域和频域内的减振性能,讨论了50~400 m不同半径的曲线线路条件下不同轮对形式的弹性车轮对中间拖车曲线通过性能的影响。计算结果显示:弹性车轮能够减小20~40 Hz、50~70 Hz和180~300 Hz频率范围内的车体垂向振动以及20~550 Hz范围内的车体横向振动。从轮对横移量和轮重减载率看,曲线半径R200 m左右是弹性车轮传统轮对和弹性车轮独立轮对曲线导向能力的分界点;从轮轨横向蠕滑率、轮对摇头角、脱轨系数和轮轴横向力看,曲线半径R100 m左右是分界点。

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。

应用于轮对主动径向控制的数字阀控液压系统研究

针对主动径向液压伺服控制系统发热量过高的问题,文章提出了一种基于脉冲编码调制技术的轮对主动径向数字阀液压控制系统方案,以高速开关阀脉冲编码调制控制代替伺服阀控制,从根源上解决热量产生的主要环节。文章介绍了脉冲编码调制数字阀控制原理,推导了脉冲编码调制数字阀控液压系统数学模型,提出了包含位置控制和压力控制的速度前馈项的闭环控制器设计方法;在完成系统的位置轨迹跟踪控制性能仿真后,搭建脉冲编码调制数字阀控液压系统试验台,开展了车辆通过曲线半径250 m线路时关于轮对的期望位置轨迹跟踪性能试验和故障工况试验。试验结果表明,系统不仅具有较好的位置轨迹跟踪控制精度,而且有较好的容错性能,为解决主动径向液压伺服控制技术应用于车辆时系统出现发热的问题提出了解决方案。

轨道交通车辆轮对表面处理技术专利分析

随着国家铁道运输和轨道交通行业的快速发展,四川省以培育轨道交通车辆装备产业集群为目标。轮对作为轨道交通车辆的关键装备,在服役中表面极易产生损伤和失效,通过不同表面处理技术可改善其表面性能。本文以产业技术应用和专利视角,分析国内外轨道交通车辆轮对用表面处理技术专利,得到该领域的国内外发展状况、趋势和方向,为四川省轨道交通装备相关技术人员在轮对表面处理技术领域研究、决策提供技术支撑和客观依据。

基于机器视觉的轮对磁粉探伤裂纹检测方法研究

为实现火车轮对荧光磁粉探伤裂纹的自动检测,提出一种基于机器视觉的裂纹识别和测量算法。基于工业相机分区采集的轮对荧光磁粉探伤图像,首先通过G通道分离处理、G通道阈值处理和高斯滤波处理等操作,降低图像噪点,提高裂纹特征对比度;然后在图像二值化和形态学处理初步提取目标区域的基础上,提出基于连通域的裂纹特征分割算法,进一步精确提取裂纹目标,并根据连通域信息完成裂纹分类和识别;最后,采用裂纹分割图像骨架细化拟合曲线的方法进行裂纹长度测量。实验表明,提出的方法可以有效精准地对轮对裂纹进行检测,查全率为98.56%,查准率为91.12%,识别速度为每幅48.5 ms。

变转速工况下基于快速谱平均峭度图的列车轮对轴承故障诊断

由于受到轮轨激励的干扰,轮对轴承故障特征易被背景噪声所淹没,且在变转速模式下故障特征具有时变性,进一步加剧了提取难度。为此,提出一种基于快速谱平均峭度图的列车轮对轴承故障特征提取方法。根据频谱趋势将频谱划分为若干子带,采用Meyer小波构造带通滤波器,计算每个窄带滤波信号的平均峭度并构造快速谱平均峭度图;选取最优频带进行解调,消除背景噪声的影响;通过相位函数对滤波信号进行迭代广义解调,解决时变故障冲击间隔带来的频谱模糊问题。仿真和试验分析结果表明所提方法有效克服了强背景噪声和时变故障特征的干扰,为变转速工况下轮对轴承故障特征提取提供了新的解决策略。

高铁轮对高精度测量系统设计与实现

针对国内轮对尺寸测量手段落后、精度不高、测量效率以及自动化水平低的问题,设计并实现了一种接触式轮对外形尺寸自动化测量系统。该系统利用接触式触发测头以及位移传感器实现了轮对外形尺寸自动化测量,并通过相对测量原理以及温度补偿算法实现了包括内侧距离、轮位、轴颈直径等长度尺寸及径向尺寸的高精度测量。通过在高铁轮对生产组装现场实际试验及试用验证,该系统的测量结果具有高精度和高一致性,满足高铁轮对各个尺寸的测量精度要求。

VMD引导的轮对与轴承复合故障诊断方法

针对列车轮对轴承系统复合故障难以辨识与诊断问题,提出一种变分模态分解(variational mode decomposition,VMD)引导的多故障特征提取匹配方法.首先,为避免预定义模式数在运行过程中对先验知识依赖从而对诊断结果造成影响,对原始轴箱振动数据进行逐阶VMD分解,模式数为2~N;其次,对VMD分解获取的本征模态函数(VMD intrinsic mode functions,VIMF)进行相关峭度计算,提取相关峭度最大的VIMF;然后,将相关峭度最大的VIMF进行平方包络分析,提取故障特征频率;最后,将所提方法与快速峭度谱、相关峭度谱方法进行对比.仿真信号和试验数据分析表明:所提方法完全规避了VMD模型中关键参数K的选择问题,可以准确、有效地分别提取出轮对和轴承的故障特征;与快速谱峭度与相关谱峭度方法相比,获取的故障特征谐波分量在数量和信噪比上均具有明显优势.