On the Polygonal Wear Evolution of Heavy-Haul Locomotive Wheels due to Wheel/Rail Flexibility and Its Mitigation Measures

Wheel polygonal wear can immensely worsen wheel/rail interactions and vibration performances of the train and track,and ultimately,lead to the shortening of service life of railway components.At present,wheel/rail medium-or high-frequency frictional interactions are perceived as an essential reason of the high-order polygonal wear of railway wheels,which are potentially resulted by the flexible deformations of the train/track system or other external excitations.In this work,the effect of wheel/rail flexibility on polygonal wear evolution of heavy-haul locomotive wheels is explored with aid of the long-term wheel polygonal wear evolution simulations,in which different flexible modeling of the heavy-haul wheel/rail coupled system is implemented.Further,the mitigation measures for the polygonal wear of heavy-haul locomotive wheels are discussed.The results point out that the evolution of polygonal wear of heavy-haul locomotive wheels can be veritably simulated with consideration of the flexible effect of both wheelset and rails.Execution of mixed-line operation of heavy-haul trains and application of multicut wheel re-profiling can effectively reduce the development of wheel polygonal wear.This research can provide a deep-going understanding of polygonal wear evolution mechanism of heavy-haul locomotive wheels and its mitigation measures.

Study on wear characteristics and authorized limits of switch rails of high-speed turnout

Purpose-It is quite universal for high-speed turnouts to be exposed to the wear of the stock rail of the switch rail during the service process.The wear will cause the change of railhead profile and the relative positions of the switch rail and the stock rail,which will directly affect the wheel-rail contact state and wheel load transition when a train passes the turnout and will further impose serious impacts on the safety and stability of train operation.The purpose of this paper is to provide suggestions for wear management of high-speed turnout.Design/methodology/approach-The actual wear characteristics of switch rails of high-speed turnouts in different guiding directions were studied based on the monitoring results on site;the authorized wear limits for the switch rails of high-speed turnout were studied through derailment risk analysis and switch rail strength analysis.Findings-The results show that:the major factor for the service life of a curved switch rail is the lateral wear.The wear characteristics of the curved switch rail of a facing turnout are significantly different from those of a trailing turnout.To be specific,the lateral wear of the curved switch rail mainly occurs in the narrower section at its front end for a trailing turnout,but in the wider section at its rear end when for a facing turnout.The maximum lateral wear of a dismounted switch rail from a trailing turnout is found on the 15-mm wide section and is 3.9 mm,which does not reach the specified limit of 6 mm.For comparison,the lateral wear of a dismounted switch rail from a facing turnout is found from the 35-mm wide section to the full-width section and is greater than 7.5 mm,which exceeds the specified limit.Based on this,in addition to meeting the requirements of maintenance rules,the allowed wear of switch rails of high-speed turnout shall be so that the dangerous area with a tangent angle of wheel profile smaller than 43.68 will not contact the switch rail when the wheel is lifted by 2 mm.Accordingly,the lateral wear limit at the 5-mm wide section of the curved switch rail shall be reduced from 6 mm(as specified)to 3.5 mm.Originality/value-The work in this paper is of reference significance to the research on the development law of rail wear in high-speed turnout area and the formulation of relevant standards.

Field investigation on effects of railway track geometric parameters on rail wear

Rail wear has dramatic impact on track performance, ride quality and maintenance costs. The amount of rail wear is influenced by various elements among which geometric parameters play an important role. The amount of wear in Iran’s railway lines and its imposed maintenance costs oblige us to make modifications on the various geometrical parameters. In order to ensure the effectiveness of these changes, it is necessary to investigate these parameters and their effects on the wear. This research is aimed at studying the effects of different track geometrical parameters on the vertical and lateral wear by conducting a three phase field investigation. The first phase was carried out at the switches of a station, the second phase at a straight line, and the third at a curved line out of the station. The results obtained are analyzed and the role of each track geometrical parameter in the rail wear is discussed. Recommendations for prevention or reduction of rail wear are presented.

Simulation of wheel and rail profile wear:a review of numerical models

The development of numerical models able to compute the wheel and rail profile wear is essential to improve the scheduling of maintenance operations required to restore the original profile shapes.This work surveys the main numerical models in the literature for the evaluation of the uniform wear of wheel and rail profiles.The standard structure of these tools includes a multibody simulation of the wheel-track coupled dynamics and a wear module implementing an experimental wear law.Therefore,the models are classified according to the strategy adopted for the worn profile update,ranging from models performing a single computation to models based on an online communication between the dynamic and wear modules.Nevertheless,the most common strategy nowadays relies on an iteration of dynamic simulations in which the profiles are left unchanged,with co-simulation techniques often adopted to increase the computational performances.Work is still needed to improve the accuracy of the current models.New experimental campaigns should be carried out to obtain refined wear coefficients and models,while strategies for the evaluation of both longitudinal and transversal wear,also considering the effects of tread braking,should be implemented to obtain accurate damage models.

Investigation into rail corrugation in high-speed railway tracks from the viewpoint of the frictional self-excited vibration of a wheel–rail system

A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.

Research on rail wear of small radius curve in EMU depot

Purpose–With the help of multi-body dynamics software UM,the paper uses Kik–Piotrowski model to simulate wheel-rail contact and Archard wear model for rail wear.Design/methodology/approach–The CRH5 vehicle-track coupling dynamics model is constructed for the wear study of rails of small radius curves,namely 200 and 350 m in Guangzhou East EMU Depot and those 250 and 300 m radius in Taiyuan South EMU Depot.Findings–Results show that the rail wear at the straight-circle point,the curve center point and the circlestraight point follows the order of center point>the circle-straight point>the straight-circle point.The wear on rail of small radius curves intensifies with the rise of running speed,and the wearing trend tends to fasten as the curve radius declines.The maximum rail wear of the inner rail can reach 2.29 mm,while that of the outer rail,10.11 mm.Originality/value–With the increase of the train passing number,the wear range tends to expand.The rail wear decreases with the increase of the curve radius.The dynamic response of vehicle increases with the increase of rail wear,among which the derailment coefficient is affected the most.When the number of passing vehicles reaches 1 million,the derailment coefficient exceeds the limit value,which poses a risk of derailment.

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.

Parameters studies for rail wear in high-speed railway turnouts by unreplicated saturated factorial design

Rail wear is one of the main reasons for reducing the service life of high-speed railway turnouts in China. The rail wear characteristics of high-speed railway turnouts are influenced by a large number of input parameters of the complex train-turnout system. To reproduce the actual operation conditions of railway turnouts, random distributions of these inputs need to be considered in rail wear simulation. For a given nominal layout of the high-speed railway turnout, 19 input parameters for rail wear simulation in high-speed railway turnouts are investigated based on orthogonal design of experiment. Three dynamic responses(wheel-rail friction work, normal contact force and size of contact patch) are defined as observed values and the significant factors(direction of passage, axle load, running speed, friction coefficient, and wheel and rail profiles) are determined by two unreplicated saturated factorial design methods, including the half-normal probability plot method and Dong 93 method. As part of the associated rail wear simulation, the influence of the wear models and the local elastic deformation on the rail wear was separately investigated. The calculation results for the wear models are quite different, especially for large creep mode. The local elastic deformation has a large effect on the sliding speed and rail wear and needs to be considered in the rail wear simulation.

Research on Wheel Rail Wear for a 140 t Open Type Hot Metal Car

To maintain the safety of an open-type hot-metal car and to reduce wheel-rail wear during transportation, simulation models of the main components of such car were built using Pro/E software and then tested. In particular, the Pro/E models were imported into ADAMS/Rail for assembly and then used to construct a complete hot-metal car dynamic model. Locomotive wheel-rail attack angle, wheel-rail lateral force, and wear index were used as evaluation parameters during the simulation to analyze the effects of bogie parameter, rail parameter, and speed of the hot-metal car on wheel-rail wear. An improvement scheme for reducing wheel-rail wear was proposed based on the result of the dynamic simulation, wherein wheel-rail wear and curving performance were analyzed and compared. The simulation provided an important reference for evaluating and improving the dynamic performance of the hot-metal car. The applied effect showed that the improvement scheme is effective.

Assessment of the curving performance of heavy haul trains under braking conditions

To study the curving performance of trains, 1D and 3D dynamic models of trains were built using nu- merical methods. The 1D model was composed of 210 simple wagons, each allowed only longitudinal motion; whereas the 3D model included three complicated wagons for which longitudinal, lateral, and vertical degrees of freedom were considered. Combined with the calculated results from the 1D model under braking conditions, the behavior of draft gears and brake shoes were added to the 3D model. The assessment of the curving performance of trains was focused on making comparisons between idling and braking conditions. The results indicated the following： when a train brakes on a curved track, the wheel-rail lateral force and derailment factor are greater than under idling conditions. Because the yawing movement of the wheelset is limited by brake shoes, the zone of wheel contact along the wheel tread is wider than under idling conditions. Furthermore, as the curvature becomes tighter, the traction ratio shows a nonlinear increasing trend, whether under idling or braking conditions. By increasing the brake shoe pressure, train steering becomes more difficult.

Typical wheel–rail profile change rules and matching characteristics of high speed railway in China

Purpose–In order to systematically grasp the changes and matching characteristics of wheel and rail profiles of high speed railway(HSR)in China,172 rail profile measurement points and 384 wheels of 6 high-speed electric motive unites(EMUs)were selected on 6 typical HSR lines,including Beijing–Shanghai,Wuhan–Guangzhou,Harbin–Dalian,Lanzhou–Xinjiang,Guiyang–Guangzhou and Dandong–Dalian for a two-year field test.Design/methodology/approach–Based on the measured data,the characteristics of rail and wheel wear were analyzed by mathematical statistics method.The equivalent conicity of wheel and rail matching in a wheel reprofiling cycle was analyzed by using the measured rail profile.Findings–Results showed that when the curve radius of HSR was larger than 2,495 m,the wear rate of straight line and curve rail was almost the same.For the line with annual traffic gross weight less than 11 Mt,the vertical wear of rail was less than 0.01 mm.The wear rate of the rail with the curve radius less than 800 m increased obviously.The wheel tread wear of EMUs on Harbin–Dalian line,Lanzhou–Xinjiang line and Dandong–Dalian line was relatively large,and the average wear rate of tread was about 0.05–0.06 mm$(10,000 km)
1,while that of Beijing–Shanghai line,Wuhan–Guangzhou line and Guiyang–Guangzhou line was about 0.03–0.035 mm$(10,000 km)
1.When the wear range was small,the equivalent conicity increased with the increase of wheel tread wear.When the wear range of wheel was wide,the wheel–rail contact points were evenly distributed,and the equivalent conicity did not increase obviously.Originality/value–This research proposes the distribution range of the equivalent conicity in one reprofiling cycle of various EMU trains,which provides guidance for the condition-based wheel reprofiling.

基于Android Wear的智能设备数据安全防护技术研究

随着移动技术的发展与智能操作系统的推广,智能设备在为用户提供便利的同时,也存在一些数据安全隐患。针对Android Wear智能手表,提出了一种通过在Linux内核层对麦克风、蓝牙和ADB等数据端口进行开关控制,以实现对手表中的数据进行保护的技术。该技术使用了两种不同的途径实现对三个数据端口的控制。同时,还实现了一种内核程序的用户交互方法,在文件系统驱动程序中截获用户层程序对特定文件的读写操作,可以显示数据端口的当前开关状态,并对开关状态进行控制,而不需要增加或修改应用层程序,最后通过实验验证了该技术的可行性。

Evolution and formation mechanism of rail corrugation in high-speed railways involving the longitudinal wheel-track coupling relationship

Rail corrugation poses a significant threat to train running safety in the field of railway engineering.Therefore,this study employs numerical analysis to investigate the evolution and formation mechanism of rail corrugation in high-speed railways(HSR).Firstly,a three-dimensional(3D)vehicle-track coupled dynamics(VTCD)model is established,which considers the longitudinal wheel-rail(WR)coupling relationship more adequately.Then,by integrating the USFD wear model into this 3D VTCD model,a long-term iterative wear model is developed to reproduce the corrugation evolution process.The predicted corrugation exhibits two distinct wavelength components and closely matches the sample obtained from China's HSR,validating the established model in terms of reliability.Furthermore,the formation mechanism of these two wavelength components is investigated by analyzing the harmonic behavior of vehicle-track coupled systems(VTCS)and the evolution law of rail corrugation under different calculation conditions.The findings reveal that the 3rd-order vertical rail local bending mode(RLBM)between two wheelsets of a bogie(TW-B)is the primary factor contributing to the formation of the long-wavelength component of rail corrugation.The discrete supports of the fasteners do not affect the 3rd-order vertical RLBM,which can be stably excited.Moreover,the vertical rail vibration has a substantial coupled effect on the longitudinal WR creep.When the 3rd-order vertical RLBM is excited,the coupled effect and the negative longitudinal WR creepage together evidently promote the formation of the short-wavelength component of rail corrugation.

DC-Rail ZVT逆变器中异步电机直接转矩控制研究

逆变器开关频率的高低是影响直接转矩控制性能的重要因素.利用一种控制简单的直流环节零电压过渡(DC-Rail ZVT)软开关逆变电路,可以大大减少开关损耗、提高开关频率,从而考虑将此软开关电路应用于异步电机直接转矩控制系统中.本文给出了软开关逆变器中异步电机直接转矩控制系统的设计思路和原则,并通过仿真试验说明了此软开关逆变器电路在直接转矩控制应用中的可行性.

一种适于Rail-to-Rail输入的2.5 V CMOS模拟采样电路

文章分析了影响低压CMOS采样电路性能的主要因素,设计了一种适合在2.5V电源下工作的CMOS自举开关采样电路。其输入信号的动态范围为0～2.5V,并给出了0.6μm标准CMOS工艺条件下的Hspice模拟结果。

Study on Match Relationship between Rail and Wheel

The match relationship between rail and wheel was studied by investigating the behavior of the contact fatigue wear in rail/wheel systems.The hardnesses of samples were close or equal to that of the real rail and wheel.Meanwhile the probe of study went further into the condition match and the material match based on the hardness match.The experimental results show that the wear rate depends on the hardness ratio(H/H)between rail and wheel,and the safe value of H/Hequals 1.00-11.20.The fatigue life of materials relies on the operating conditions except hardness.The selected experimental conditions satisfy the condition match except Rheat-treated out-line.The factor H/Sis the main element effecting wears in rail steel and wheel steel.The nature of the hardness match is the microstructure match under specified operating conditions.

Improving rail vehicle dynamic performance with active suspension

Today,it is difficult to further improve the dynamic performance of rail vehicles with conventional passive suspension.Also,simplified vehicle respectively running gear layouts that significantly could reduce vehicle weights are difficult to realize with modern requirements on passenger vibration comfort and wheel and rail wear.Active suspension is a powerful technology that can improve the vehicle dynamic performance and make simplified vehicle concepts possible.The KTH Railway group has,together with external partners,investigated active suspensions both numerically and experimentally for 15 years.The paper provides a summary of the activities and the most important findings.One major project carried out in close collaboration with the vehicle manufacturer Bombardier and the Swedish Transport Administration was the Green Train project,where a 2-car EMU test bench was used to demonstrate different active technologies.In ongoing projects,a concept of single axle-single suspension running gear is developed with active suspension both for comfort improvement and reduced wheel wear in curves.The results from on-track tests in the Green Train project were so good that the technology is now implemented in commercial trains and the simulation results for the single-axle running gear are very promising.

钢轨材料局部激光熔覆自熔性合金涂层的磨损与滚动接触疲劳行为

激光熔覆技术可用于钢轨局部损伤表面的局部修复,但局部修复钢轨材料的磨损与滚动接触疲劳损伤规律尚不清楚。通过在钢轨试样表面切除凹槽来模拟局部损伤,在凹槽处激光熔覆Ni基、Fe基和Co基自熔性合金粉末,分析修复钢轨微观组织与硬度,然后利用双轮对滚试验研究局部修复钢轨试样的磨损与滚动接触疲劳行为。结果表明,激光熔覆涂层形成了共晶与枝晶组织,Ni基涂层组织粗大、硬度较小,Fe基与Co基涂层组织尺寸较小,Fe基涂层硬度最大,Co基涂层硬度居中。相比未熔覆区域,激光熔覆区(涂层)塑性变形层厚度较小,且涂层原始硬度越高,硬化后硬度越大,但硬化率和硬化层厚度更小。未熔覆区滚动接触疲劳裂纹较长,但裂纹角度较小;熔覆区裂纹长度均有所降低,但裂纹扩展角度明显增大;熔覆区与未熔覆区结合处疲劳损伤最为严重,疲劳裂纹角度和深度均比熔覆区和未熔覆区更大。对比分析发现,Stellite21(Co基)熔覆试样摩擦因数较低,熔覆区与未熔覆区磨损深度差较小,抗滚动接触疲劳性能较好,较为适合钢轨局部损伤的激光修复。研究结果可为激光熔覆技术在钢轨局部修复上的应用与优化提供理论与技术指导。

不同牵引特性城轨列车车轮磨耗与疲劳研究

针对列车频繁牵引起动对车轮磨耗与疲劳损伤产生的影响问题,在恒定牵引力的基础上,探究了不同牵引特性曲线恒功率区转折点速度对车轮磨耗与疲劳的影响规律。采用SIMPACK和MATLAB软件进行联合仿真,建立了不同牵引特性下城轨列车动力学模型和基于Archard的车轮磨耗模型,分析在牵引电机不同起动转矩下牵引特性曲线恒功率区转折点速度对城轨列车轮轨蠕滑率、车轮磨耗深度、磨耗面积以及疲劳指数的影响规律。结果表明:列车牵引起动过程中,电机起动转矩越大,轮轨蠕滑率、车轮磨耗深度和磨耗面积也越大,而疲劳指数则越小;电机起动转矩一定时,随着列车牵引特性曲线恒功率区转折点速度的增大,轮轨蠕滑率、车轮磨耗深度和磨耗面积也增大,疲劳指数则有所减小;当电机起动转矩从800 N·m增大到1400 N·m,车轮磨耗深度和磨耗面积增长率最大为6.9%和12.6%,而疲劳指数下降率最大为7.2%;当恒功率区转折点速度从50 km/h增加到80 km/h,车轮磨耗深度和磨耗面积增长率最大为4.4%和4.3%,疲劳指数下降率最大为1.9%。本文研究了车辆起动转矩与恒功率转折点速度变化对车轮磨耗与疲劳的影响规律,可为车辆牵引特性设计和电机控制以及车轮运维提供参考。

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。