Parametric investigation of railway fastenings into the formation and mitigation of short pitch corrugation

Short pitch corrugation has been a problem for railways worldwide over one century.In this paper,a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation.A three-dimensional finite element vehicle-track dynamic interaction model is employed,which considers the coupling between the structural dynamics and the contact mechanics,while the damage mechanism is assumed to be differential wear.Various fastening models with different configurations,boundary conditions,and parameters of stiffness and damping are built up and analysed.These models may represent different service stages of fastenings in the field.Besides,the effect of train speeds on corrugation features is studied.The results indicate:(1)Fastening parameters and modelling play an important role in corrugation formation.(2)The fastening longitudinal constraint to the rail is the major factor that determines the corrugation formation.The fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components.(3)The strengthening of fastening constraints in the longitudinal dimension helps to mitigate corrugation.Meanwhile,the inner fastening constraint in the lateral direction is necessary for corrugation alleviation.(4)The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation propensity.The simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength components.It can also explain the field data with respect to the small variation between the corrugation wavelength and train speed,which is caused by frequency selection and jump between rail longitudinal compression modes.

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 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 Kalkers 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.

Investigation into the Vibration of Metro Bogies Induced by Rail Corrugation

The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.

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 railcorrugation is primarily investigated with numerical method in the situation of wheelset curvingsteadily and repeatedly. In the numerical analysis of corrugation it is considered that acombination of Kalker's rolling contact theory with non-Hertzian to be modified, a linear frictionalwork model and a vertical dynamics model of railway vehicle coupled with a curved track. And theuneven support stiffness of rail in the vertical direction due to discrete sleeper support and thedifferent running speed of the wheelset are taken into consideration. The damage on the runningsurface of rail, concerning rail corrugation formation, is restricted to wear mechanism of railmaterial. The numerical results obtained indicate that the discrete supports of rail by sleepershave a great influence on the formation of the corrugation under the condition of non-zero andstable creepages of wheelset and track.

Experimental and simulation investigation into the cause and treatment of rail corrugation for metro

The cause and treatment of rail corrugation for the metro have always been a popular and challenging issue. In this work, the field measurements were carried out on rail corrugation, track stiffness, and the track dynamic response. A three-dimensional finite element model was developed to investigate the cause of rail corrugation. The constraints on rail vibration from two wheelsets and adjacent wheel-rail interactions were taken into account in the model. According to experimental and simulation results, the suppression measure for rail corrugation was proposed and the suppression mechanism was discussed. It was found that the cause of rail corrugation is related to vertical and lateral vibration of the rails outside the two wheelsets at around 380 Hz. The increased stiffness of the fasteners reduces the vibration energy of the rail and the wheel-rail force. However, simply increasing the stiffness of the fasteners may not be effective in the suppression of rail corrugation. If necessary, the rails need to be grinded to reduce the roughness to a certain level, so that increasing the fastener stiffness can effectively suppress the rail corrugation.

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.

Slip-Stick Vibrations of Wheelsets and Rail Corrugations

A dynamic space coupling model is developed for simulating the vibrations of wheel/rail systems as well as the torsion and bending vibrations of wheelsets. It is found that the slip stick vibrations of wheelsets are mainly caused and controlled by the crossing excitation or self excitation of the vertical vibrations of the whole system and by the bending vibrations and torsion vibrations of the wheelsets. It is found for the first time that the slip stick vibrations may occur in more than one forms, and one or another of the three kinds of vibrations is excited more strongly. Four typical kinds of slip stick vibrations are enumerated and described. The field investigation on rail corrugations shows that the four kinds of slip stick vibrations are most likely to exist and related with different corrugated features.

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.

基于波噪比的高速铁路钢轨波磨快速检测方法

为实现高速铁路钢轨波磨里程覆盖式、高频次、快速测量,提出基于波噪比的钢轨波磨快速检测方法。采用便携式添乘仪检测高速列车车体振动和车内噪声数据,提出基于车体纵向加速度进行数值积分来计算列车速度和里程,采用曲线地段车体摇头角速度里程与台账里程的偏差值修正速度积分误差。利用提取的里程修正后车厢噪声数据与钢轨波磨对应的400~700 Hz频带成分,计算频带能量占噪声总能量的比值,并获取波噪比超限时的钢轨波磨波长和里程。结合高速列车实测数据分析,研究结果表明:速度修正后列车定位里程最大误差为87 m,对波磨比大于0.3的线路区段进行钢轨波磨波形测量和轴箱加速度振动能量比分析,钢轨波磨波长范围为53~57 mm,实测波长为53 mm,验证了该方法的正确性,为高速铁路钢轨波磨的快速测量提供技术支撑。

扣件刚度非线性对波磨区轮轨瞬态滚动接触行为的影响

WJ-8型扣件橡胶垫板刚度在长期服役过程中表现出非线性特征,静刚度随荷载增加而降低,为提高三维瞬态滚动接触有限元模型计算精确性,本文以LMA踏面车轮及CHN60型钢轨为基础,基于显式积分算法,将以往研究中线弹性扣件转化为非线性扣件,建立考虑扣件刚度非线性特征的三维轮轨瞬态滚动接触有限元模型,研究刚度非线性对车轮与钢轨波磨间高频动态响应及瞬态接触行为的影响,并重点分析了波磨工况下时频域内轮轨接触力、轴箱加速度的变化信息.结果表明:扣件非线性对轮轨接触力变化影响明显,主要表现为车轮行驶至扣件前端时强振动导致橡胶垫板表现为柔软特性使轮轨接触力减小,车轮行驶至扣件上方时在轴重作用下振动减弱表现为刚硬特性使轮轨接触力增大,轮轨力变化差异最大达到13.1%.

地铁钢轨波磨对车辆-轨道振动及噪声特性的影响

钢轨波磨作为地铁线路中最为常见的轨道损伤问题之一,始终未得到根本性的解决。为研究不同轨道结构形式产生钢轨波磨后车辆内部振动噪声以及轨道结构振动的时频域特性,探究钢轨波磨对车辆和轨道的影响,对某地铁线路进行现场动静态测试,获取了钢轨波磨激励下车辆内部的振动和噪声响应以及轨道各部件的振动响应,使用时域指标统计、1/3倍频程谱分析等方法分析轨道振动响应特征和车内振动及噪声响应特征。结果表明:在小半径曲线地段,浮置板轨道产生了特征波长约为200 mm的钢轨波磨,整体道床轨道产生了特征波长约为60 mm的钢轨波磨;浮置板轨道的钢轨、道床板、隧道壁振动加速度有效值分别是整体道床的1.8、5.8倍及0.3倍;钢轨波磨对轨道振动的影响主要体现在中高频范围,在300~400 Hz附近,浮置板轨道振级从钢轨至隧道壁共衰减66 d B,而整体道床共衰减49 d B;列车通过测试区域时,转向架上方与客室中部垂、纵向振动加速度有效值基本一致,而客室中部横向振动加速度有效值约为转向架上方的2倍;车内转向架位置处的异常振动主要来源于钢轨波磨的激励,且短波长波磨所激励的车内振动及噪声更加剧烈。因此,地铁钢轨波磨产生后在轨道及车辆的振动噪声响应中均占主要成分,应及时对钢轨进行打磨处理,研究结果可为地铁工务维修提供理论指导。

钢轨短波波磨对轨道振动俘能器发电性能的影响规律研究

以轮轨摩擦自激振动理论和轨面不平顺反馈振动理论为基础,结合钢轨波磨与轨道振动能量回收两个研究方向,通过建立考虑钢轨波磨的“车轮-钢轨-吸振器”振动分析模型与轨道振动俘能器分析模型,研究了不同波深与波长的钢轨短波波磨对轨道振动俘能器的输出功率的影响规律。分析结果显示,波磨深度的增大会导致轮轨接触力和轨面垂向加速度的振幅增大,但不会影响钢轨的主振频率。波磨波长的增大会导致轮轨接触力和轨面垂向加速度的振幅先增大后减小,钢轨的主振频率随波磨波长的增大而减小。轨道振动俘能器的输出功率会受到波磨深度和波长的影响,表现为波长不变时,波深增加,俘能器的输出功率提高。波深不变时,波长增加,俘能器的输出功率先增大后减小,但仍大于光滑轨道上俘能器的输出功率,并且,采用小波包分解方法得到小波包能量值与波磨波长几乎呈线性关系。上述分析结果表明,该轨道振动俘能器在高效回收轨道振动能量的条件下,能有效地监测钢轨波磨的产生过程和预测钢轨波磨的近似波长。

高速铁路钢轨波磨地段轴箱振动加速度时频特征分析

钢轨波磨是一种常见的高速铁路轨道病害。为了研究钢轨波磨参数与轴箱加速度响应时频特征之间的对应关系,从理论上探索通过轴箱振动加速度识别钢轨波磨的可行性,基于车辆-轨道耦合动力学理论建立了考虑车辆主要部件柔性化的刚柔耦合动力学模型。通过与实测数据的对比,验证了模型的准确性;在研究了钢轨波磨参数与轴箱振动加速度时域信号之间因应关系的基础上提出了一种基于VMD-SPWVD的钢轨波磨时频分析方法,并验证了该方法的有效性。研究结果表明,钢轨波磨会对轴箱振动加速度信号产生较大影响;不同波深和波长下的轴箱振动加速度最大值在时域信号中的位置具有随机性;钢轨波磨参数与轴箱振动加速度均方根之间的规律性较为明显,但其作为一种时域指标无法准确定位波磨区段的位置和严重程度;相较于时域分析方法,本文提出的基于VMD-SPWVD的时频分析方法能有效反映钢轨波磨参数与轴箱振动加速度之间的因应关系,时频分析结果能准确得到钢轨波磨的特征频率且不存在干扰成分,能量幅值与钢轨波磨波深之间呈正相关,该方法可以定位波磨存在的区段并能够体现同一区段不同位置波磨的严重程度。最后采用该方法对实测数据进行分析,进一步验证了本文所述方法通过轴箱振动加速度信号识别钢轨波磨的有效性。

地铁曲线波磨地段振动特性影响因素分析

为研究地铁曲线波磨地段振动特性影响因素,建立车辆-轨道及轨道-隧道-大地模型,分析不同波磨波深、隧道埋深、轨道减振措施下隧道壁及地面的振动响应。结果表明:减小钢轨波磨波深或增加隧道埋深,隧道壁和地面的垂向最大加速度和加速度分频最大振级均有减小趋势;采取不同轨道减振措施时,浮置板的减振效果最佳;隧道埋深和轨道减振措施的改变,不会改变隧道壁和地面加速度峰值的频段区间及加速度分频最大振级的中心频率;振动在隧道壁传递到地面的过程中高频衰减较快。

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。

宽频式钢轨动力吸振器对波磨的影响分析

为了解决某地铁钢弹簧浮置板轨道曲线段钢轨波磨问题,首先对钢轨波磨进行了现场测试,其次依据波磨特征进行宽频式钢轨动力吸振器(wide-frequency tuned mass damper,WTMD)的精准调频和研制。然后将WTMD的质量、刚度和阻尼等参数输入到建立的车辆-WTMD-钢弹簧浮置板耦合动力学模型。模型中浮置板和基础考虑为柔性体,轮轨接触采用多点非赫兹接触的Kik-Piotrowski模型求解。以美国5级谱叠加现场实测的波磨不平顺谱作为激励,运用有限元软件ANSYS和多体动力学仿真软件UM进行联合耦合动力学分析,逐次迭代优化WTMD参数。同时,将有无WTMD的仿真分析得到的钢轨振动加速度和现场实测数据进行对比,研究了WTMD对钢轨振动的影响。最后进行了有无WTMD的钢轨振动总振级、钢轨振动衰减率和3次波磨跟踪测试,研究了WTMD对钢轨振动、钢轨振动衰减率和波磨发展的影响。研究表明:设计的WTMD前3阶振动主频分别为518、700、759 Hz,与车辆通过波磨频率(520~830 Hz)一致;仿真和实测的钢轨振动加速度数据吻合较好,安装WTMD后钢轨振动加速度均方根值由200 g降低为20 g,减振效果为8.1 dB;WTMD可以提高钢轨的垂向和横向振动衰减率,抑制钢轨的垂向和横向pinned-pinned共振;3次波磨跟踪测试发现,WTMD安装后,钢轨波磨发展缓慢,无肉眼可见的波磨。通过以上的仿真和试验都验证了WTMD可以有效地抑制钢轨波磨。

基于图像处理技术的车载钢轨波磨自动识别与预警系统

[目的]目前地铁轨道日常巡检采用的人工检测和轨道检查车方式存在效率低、成本高等问题,已无法满足日益发展的轨道交通安全运营需求。对此,需要基于图像处理识别技术,研究车载钢轨波磨自动识别与预警系统。[方法]阐明了钢轨波磨自动识别的总方案,从钢轨表面图像的去噪与光照不均校正问题及钢轨表面图像的定位与分割、钢轨波磨区间的定位、钢轨波磨周期估计等方面,详细阐述了基于图像处理的钢轨波磨自动识别与评估方法。基于系统构成和逻辑架构从软硬件角度分别描述了病害自动识别与预警系统的构建,并介绍了该系统在北京地铁的示范应用情况。[结果及结论]该系统能实现对轨道波磨病害的实时检测、定位、评估及预警。示范应用测试结果表明:该系统的钢轨波磨病害识别准确率达到97%以上;与传统人工巡检和专用轨道检测车相比,检测效率极具优势。

钢轨调频阻尼器质量分布与性能研究

为研究减振块中谐振质量分布对钢轨调频阻尼器动力性能的影响,采用数值仿真与平台试验相结合的方法,对比分析不同谐振质量体分布下的钢轨调频阻尼器在典型频率和钢轨振动衰减率方面的差异,并分别选取2个试验段,采用现场测试的方法对钢轨调频阻尼器在减振垫浮置板轨道、减振扣件轨道结构下的钢轨振动以及轨旁噪声控制效果进行分析。研究结果表明:减振块中质量体的分布影响减振块的模态频率、有效频段和分频吸振效能,上层质量体及邻近弹性层厚度确定了垂/横向1阶频率,近轨侧弹性层厚度及总质量确定了吸振能力最高的频率。钢轨调频阻尼器的模态频率与试验平台垂向振动衰减率峰值频率和衰减率增加的显著频段一致性较好,可根据模态频率和参振质量比对减振块质量分布进行优化。经平台试验,前十五阶模态参振质量低与高的两款钢轨调频阻尼器安装后,钢轨振动衰减率最大值由安装前的0.53dB/m分别提升至3.54dB/m和4.07dB/m,钢轨垂向振动衰减率分频最大增加率分别为1143%和2023%。由现场测试结果可知,安装调频钢轨阻尼器可降低减振垫浮置板轨道1~1000 Hz频段钢轨振动加速度总级值5.6 dB,降低波磨主频处分频振级2.2~5.8 dB,并有效降低钢轨表面粗糙度发展速度;安装后可降低高等级减振扣件轨道轨旁噪声6.1 dB(A)。研究成果可为钢轨调频阻尼器的结构设计及优化提供参考。

某地铁转向架构架端部开裂机理及分析

针对某B型地铁在正常运营过程中发生转向架构架端部开裂问题,文中采用运营模态分析和线路试验开展断裂机理研究。首先文中基于PolyMAX方法识别出构架在实际运营中的工作模态,其中构架端部存在频率为222.9 Hz,阻尼比为0.72%的纵向摆动固有模态;然后通过分析轴箱、构架端部加速度和动应力时频特性以及对典型区间轨道调查发现,车辆以60 km/h的运营速度通过含有波长为80 mm钢轨波磨的弹性短轨枕区段时,构架端部与轨道固有频率重合,从而导致结构共振引发疲劳破坏;在相同工况条件下,构架端部安装加强筋改进后的结构,其振动加速度和动应力均比原方案减小90%左右,同时对改进前后构架端部进行寿命评估,结果表明安装加强筋后的构架端部损伤值大幅降低,满足转向架的使用寿命要求。