A vertical coupling dynamic analysis method and engineering application of vehicle–track–substructure based on forced vibration

Purpose–This study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.Design/methodology/approach–The track and substructure are decomposed into the rail subsystem and substructure subsystem,in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener.The rail is treated as a continuous beam with elastic discrete point supports,and spring-damping elements are used to simulate the constraints between rail and fastener.Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system,while the external load is used to deal with the reverse effect.The fastener failure is simulated with the methods that cancel the forced vibration transmission,namely take no account of the substructure–rail interaction at that position.Findings–The dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method.Local fastener failure will slightly affect the vibration of substructure and carbody,but it will significantly intensify the vibration response between wheel and rail.The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value,respectively,under the train speed of 350 km$h
1.At the same time,the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%,respectively,from the normal value.Originality/value–This method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.

Distribution characteristics and influencing factors of the frequency-domain response of a vehicle–track vertical coupled system

Employing theory on vehicle-track coupled dynamics, the equation of motion of a vehicle-track vertical coupled system was established by combining frequency analysis and symplectic mathematics. The frequency response of the vehicle-track vertical coupled system was calculated under the excitation of the German low-interfer- ence spectrum, and the effects of the vehicle speed, vehicle suspension parameters, and track support parameters on the frequency response of the coupled system were studied. Results show that, under the excitation of the German low- interference spectrum, the vertical vibration of the car body is mainly concentrated in the low-frequency band, while that of the bogie has a wide frequency distribution, being strong from several Hertz to dozens of Hertz. The vertical vibrations of the wheel-rail force, wheelset, and track structure mainly occur at a frequency of dozens of Hertz. In general, the vertical vibration of the vehicle-track coupled system increases with vehicle speed, and the vertical vibrations of the car body and bogie obviously shift to higher frequency. Increasing the vehicle suspension stiffness increases the low- frequency vibrations of the vehicle system and track struc- ture. With an increase in vehicle suspension damping, the low-frequency vibrations of the car body and bogie and the vibrations of the wheel-rail vertical force and track structure decrease at 50-80 Hz, while the mid-frequency and high- frequency vibrations of the car body and bogie increase. Similarly, an increase in track stiffness amplifies the vertical vibrations of the wheel-rail force and track structure, while an increase in track damping effectively reduces the vertical vibrations of the wheel-rail vertical force and track structure.

Interaction of subway LIM vehicle with ballasted track in polygonal wheel wear development

This paper develops a coupled dynamics model for a linear induction motor （LIM） vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen– Hedrick–Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system （LMS）, Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.

The effect of subgrade inhomogeneity induced by freeze-thaw on the dynamic response of track-subgrade system

The developed vertical coupling model of Vehicle-Track-Subgrade which considered subgrade layer vibration is present- ed. The equations of motion for the ballast, top and bottom subgrade layers are presented in detail. Through inputting different coefficients, the dynamic response of track-subgrade system in a seasonal frozen region in different seasons is obtained by the developed model and the uneven freeze-thaw action of subgrade soil is presented in this model. The ef- fect of subgrade inhomogeneity induced by uneven freeze-thaw on the dynamic response of track-subgrade system was studied and the conclusions are as follows. The force at the interface of ballast and top subgrade layer and the defor- mation of ballast induced by a passing train changed sharply at the stiffness mutation zone. The force and deformation decreased with increasing stiffness ratio with the same amplitude of irregularities as the excitation source. The force and deformation were larger with larger amplitudes of irregularities. There was an obvious effect of uneven deformation and stiffness of subgrade on the dynamic response of track-subgrade system.

波浪荷载作用下车辆-轨道-悬浮隧道动力响应研究

为实现波浪荷载作用下车辆-轨道-悬浮隧道系统耦合动力学行为模拟和分析,基于车辆-轨道耦合动力学理论,引入轮轨非线性时变单元矩阵法和结构单元多尺度耦合法,采用弹簧-阻尼单元模拟锚索系统,建立车辆-轨道-悬浮隧道动力相互作用模型;根据线性波浪理论和Morison方程,确定波浪荷载计算方法;最后,基于所建立的车辆-轨道-悬浮隧道动力相互作用模型开展数值仿真模拟,研究波浪荷载作用下锚索等效刚度、波浪高度、行车速度等参数变化时系统振动响应特性及传播规律。研究结果表明:锚索等效刚度变化对轨道-悬浮隧道系统结构位移的影响显著,提高锚索等效刚度能够有效抑制结构位移增大,且考虑部分锚索失效后系统结构位移变化较大,位移增幅均大于43%,不利于结构稳定;轨道-悬浮隧道系统结构的横向位移主要由波浪荷载引起,随着波浪高度增加,轨道-悬浮隧道系统结构位移整体上呈增大趋势;在工程设计过程中,应充分调研场地水环境,并合理设置轨道-悬浮隧道系统的结构参数,以确保系统的安全性和稳定性。

车辆-轨道系统动力极值预测及可靠度计算

为从车辆-轨道系统的动力极值预测及其可靠度计算角度分析车辆系统行车安全、衡量系统可靠程度,基于车辆-轨道耦合动力学及概率理论,提出一种车轨系统动力极值预测及可靠度评估方法。首先,基于轨道不平顺概率模型,采用轨道不平顺累计概率谱确定具有不同激振能量的随机不平顺序列;依据离散Parseval定理,建立轨道不平顺时域序列和功率谱间的对应关系;将轨道不平顺概率模型与车辆-轨道耦合动力学模型相结合,从随机动力计算中提取车辆-轨道的动力极值及可靠度信息;随后利用车辆-轨道耦合动力模型及二维插值算子,根据谱线能量关系实现动力极值预测;此外,基于此系统激励输入与响应输出间的概率等效性,导出了动力极值的可靠度计算式。以实测的轨道不平顺和车体加速度数据及4种类型不平顺在不同累计概率下的谱组合计算得出的轮轨横向力和钢轨垂向位移的计算结果为样本,与预测结果进行对比。研究结果表明:计算时程的分布趋势基本与实测时程一致,动力极值预测结果与实际的动力计算结果较为接近。由于轨道不平顺随机性的存在使得车辆-轨道系统的动力响应存在随机离散及方差特征,但通过轨道不平顺的幅频及能量特性预测车辆-轨道系统的动力极值的方法是较为可行的。

Dynamic performance of heavy-haul combined train applying emergency braking on straight line

A heavy-haul train-track coupled model is developed. Taking the emergency braking of the 2×104 t combined train as example, the train longitudinal impulse, the coupler dynamic behaviors and wheel-rail interactions of vehicles distributing in the different positions are analyzed. The results indicate that under the coupler compressing forces, the couplers of middle locomotives may tilt to the free swing limits, which induces the unidirectional tilt of their connected wagon couplers. Consequently, the coupler longitudinal forces produce the lateral components, and then affect the wheel-rail dynamic interaction. The performance of the middle locomotive and their neighboring freight wagons deteriorate significantly, becoming the most dangerous parts in the combined train. The wagons disconnecting with the locomotives can basically keep their couplers to stabilize in the centering positions, even though the maximum coupler longitudinal force acts on it. And its corresponding running safety also has little changes.

钢弹簧失能下车辆-浮置板轨道耦合系统动力特性研究

在列车荷载作用下浮置板轨道会发生钢弹簧失能,为研究此问题对车辆-浮置板轨道系统动力特性的影响,基于车辆-轨道动力学理论,建立车辆-浮置板轨道耦合动力学模型,研究不同钢弹簧失能数量、位置、组合形式对车辆-浮置板轨道系统动力响应的影响。结果表明:当钢弹簧失能数量相同时,同一块浮置板的振动响应板中位置大于板端位置;钢弹簧失能1个时,板中位置钢轨、浮置板位移最大值分别比板端位置大0.49 mm和0.22 mm,加速度有效值分别比板端位置大13.34%和21.42%;单侧连续失能钢弹簧数量≥2个时,列车荷载作用下钢轨和浮置板垂向位移最大值均分别超出《浮置板轨道技术规范》规定的限值4 mm和3 mm;车体在频域上的振动响应主要集中在10 Hz内,钢弹簧失能会导致车体振动响应在频域上增大;单侧钢弹簧失能2个比双侧失能2个的钢轨位移最大值、加速度有效值分别增大17.75%、2.22%,比正常状态下钢轨位移、加速度分别增大37.08%,10.84%。钢弹簧失能增加了系统的振动响应,影响减振效果,应注意及时检修。

惯性增强动力吸振器-浮置板轨道低频减振性能研究

浮置板轨道(floating slab track, FST)对低频车轨耦合振动具有放大作用,由此引起的低频环境振动难以解决。引入惯性增强动力吸振系统(inerter enhanced dynamic vibration absorber, IDVA),提出带有IDVA的FST,即FST-IDVA,以减小列车移动荷载下的低频振动影响。理论分析给出浮置板轨道结构等效单自由度系统;考虑轮轨激励随机性,应用H_(2)优化理论给出IDVA的设计参数理论解;开发一种Matlab-Ansys联合仿真技术,应用该技术计算8编组列车运行过程中的车轨耦合动力响应。对比无动力吸振器和普通动力吸振器,验证惯性增强动力吸振器对浮置板轨道低频振动的抑制性能。研究结果表明,移动车辆荷载作用下,应用惯性增强动力吸振器后,FST板在其基频处加速度响应、钢弹簧支反力、单块板传往基础的合力均得到有效减小。惯容器的动态质量效果使吸振器与FST之间的相对位移减小大于50%。该技术可在浮置板轨道有限空间内实现更好的低频减振性能。

基于DEM-MBD对履带车辆在不同颗粒尺寸砂地行驶性能分析

为研究地面颗粒尺寸大小对履带车辆行驶性能的影响,利用DEM-MBD耦合软件对履带车辆行驶进行仿真,地面条件设置为砂地,并结合履带-地面力学对仿真结果进行分析。对履带车辆行驶偏移和沉陷量分析,得出砂地颗粒尺寸越大,履带行驶偏移量越大,沉陷量越少。本文可为履带车辆优化设计提供基础。

扣件失效对车-轨-路-地耦合系统垂向振动特性影响研究

通过有限元软件Abaqus和多体动力学软件UM联立仿真,从刚柔耦合的角度建立了车辆-轨道-路基-地基耦合振动分析模型,对比分析了正常工况、单侧扣件失效1个、3个、5个和两侧扣件失效1~5对等工况对整个系统动力响应的影响规律。研究结果表明:单侧扣件失效5个时,对钢轨垂向位移和垂向加速度影响较大,对车体垂向加速度影响较小;两侧扣件失效工况下,2.5~5对扣件失效时钢轨垂向位移超过标准规定的最大允许值2mm;轨道板和基床表层垂向振动加速度变化趋势几乎一致,与正常工况相比皆增加了约4倍,轨道板和基床表层垂向位移较正常工况变化量不大;出现非对称扣件失效时脱轨系数和轮重减载率发生突变,此时车辆脱轨风险较高。

车辆-轨道系统振动响应分析——Timoshenko梁与Euler梁轨道模型的比较

近年来,铁路的高速化、高运量化以及轻微的地震灾害等因素加速了轨道结构的沉降或变形,导致车辆轨道系统振动的加剧。本文运用车辆-轨道耦合动力学理论,编制了基于Timoshenko梁钢轨模型的车辆-轨道耦合振动仿真分析软件,分析了车辆-轨道系统的垂向振动特性,并与基于Euler梁模型的VICT软件的仿真结果进行了比较分析。结果表明:仿真结果与VICT的仿真结果基本一致,但在较高频域,前者能更好地反映轮轨系统的高频特性。因而,在研究轮轨高频振动及轮轨噪声时,采用Timoshenko梁钢轨模型更具合理性。

基于多车精细建模的曲线地段重载列车-轨道系统动力性能研究

建立考虑多车效应的重载列车-轨道系统精细化动力分析模型，对车辆、钩缓装置中各种细部构件及部件间接触摩擦等作用机制进行精细模拟，基于Hertz理论及FASTSIM算法进行轮轨接触计算。利用自主研发设备通过现场参数试验进行轨道建模。深入研究重载铁路曲线地段列车-轨道系统动力性能及曲线参数影响规律。结果表明，缓和曲线地段轮轨相互作用规律复杂，列车不同位置车轮受力呈现迥异变化趋势及幅度，前后缓和曲线轮轨相互作用亦完全不同，主要由超高顺坡及车辆构造所致；缓和曲线长度过短可导致超高顺坡过大不利列车运行，缓和曲线长度对动力性能影响曲线往往存在拐点，建议以拐点值限定最小缓和曲线长度；增长缓和曲线可有效减弱轮轨相互作用，并主要通过减缓列车首车及导向轮对磨耗降低整体磨耗；随缓和曲线长度不断增加，对动力性能改善效果越不明显。我国重载铁路小半径曲线超高设置通常偏大，建议适当降低超高值、设置10％～20％欠超高，利于改善轮轨受力、减缓磨耗。增大曲线半径利于减弱轮轨相互作用及磨耗，但半径越大改善作用越小。

基于动柔度法的车-线-桥垂向耦合振动分析

利用动柔度的思想建立高速铁路车辆-轨道-桥梁垂向耦合动力学频域模型。将车辆看作具有10自由度的多刚体系统,推导出车辆系统的动柔度;将钢轨看作无限长Timoshenko梁、轨道板简化为自由-自由的Euler梁、桥梁简化为简支Euler梁,扣件系统和CA砂浆层用线性弹性阻尼单元模拟,从而建立线-桥垂向动力相互作用系统,利用动柔度的思想求得线-桥垂向动力相互作用系统的动柔度;利用线性化Hertz接触理论,将车辆系统与线-桥垂向动力相互作用系统耦合成车-线-桥垂向耦合振动模型。分别求解单位简谐激励、轮轨几何粗糙度激励下的轨道系统和桥梁结构的动力学响应,最后结合虚拟激励法求解轨道谱激励下的轨道系统和桥梁结构的随机振动响应。研究结果表明:利用动柔度思想建立的频域车辆-轨道-桥梁垂向耦合动力学模型,具有逻辑清晰、求解快速的特点,能够直接求解系统在频域的动力学响应。

车辆-轨道耦合系统中基于变参数的三维图形仿真研究

建立一个随参数改变而改变的三维可视模型 ,是机车车辆 -轨道耦合系统动力学可视化的一个急待解决的重要问题 .文中将可视化、三维建模技术引入机车车辆 -轨道耦合动力学仿真中 ,系统地研究了机车车辆轨道耦合系统的基于变参数的三维图形仿真的方法 .综合建立了车辆模型的动态装配三维图形系统 ,直、曲线轨道的的三维离散结构等 ,为机车车辆 -轨道耦合动力学仿真建立了一个有效的可视化综合仿真平台 .

改进希尔伯特-黄变换分析波磨对列车时频特征的影响

本文旨在研究钢轨波浪形磨损对列车时频特征的影响.建立了车辆/轨道空间耦合模型,模拟计算了钢轨短波、长波波磨激励下车辆系统的动力响应.将集成经验模态分解(Ensemble Empirical Mode Decomposition,EEMD)和正交希尔伯特变换(Normalized Hilbert Transform,NHT)应用于车辆/轨道耦合系统的振动信号分析中,分析了不同波深和波长的波磨对转向架动力响应时频特征的影响.结果表明:波磨会引起车辆系统振动响应的频率调制,频率振幅与平均频率之比可作为轮轨冲击的预警指标.

基于改进的EMD方法提取车辆-轨道垂向耦合系统动态特性

提出利用一种改进的经验模态分解(EMD)方法提取车辆-轨道耦合系统的动力学特性。该方法以改进的极值域均值代替极值点包络线的均值来提高局部均值的求解精度,以边界波形匹配预测法来抑制端点效应。基于车辆-轨道耦合动力学理论,建立客车-弹性支承块无砟轨道垂向耦合动力学模型,计算车辆-轨道耦合系统在波浪形磨损和轨道不平顺组合激励模型下的振动响应。运用改进的EMD方法对系统的振动响应进行经验模态分解,并且对轮轨力、转向架和车体加速度的本征函数进行分析和比较。研究结果表明:改进的EMD方法自适应地将振动响应分解成本征函数,能有效地提取车辆-轨道耦合系统的动力学特性。

基于UM的车辆-轨道耦合动力学建模及仿真分析

基于多体系统动力学理论,分析某动车各构造拓扑关系及其力学特性,利用多体动力学软件UM建立50个自由度的车辆-轨道动力学模型,仿真分析了车辆的非线性临界速度、脱轨系数、振动加速度及平稳性指数等动力学特性,获得了该型动车直线运行的非线性临界速度477km/h;以200km/h的时速通过曲线半径R=4 000m的曲线线路时车体横向、垂向Sperling平稳性指数分别为2.01和1.69;车体横向、垂向加速度分别为0.062g和0.046g;1位轮对的最大脱轨系数和轮重减载率分别为0.182和0.406 4.研究结果表明:该型动车具有较好的动力学性能.

一系螺旋弹簧动刚度对车辆-轨道耦合振动影响分析

建立准确表征一系悬挂轴箱螺旋弹簧波动特性的力学模型,运用动刚度矩阵法求解,研究其对悬挂系统隔振性能影响。结合基于格林函数法的车辆-轨道耦合动力学模型,引入弹簧刚度频变特性,对比分析考虑一系螺旋弹簧频变刚度前后车辆动力学性能之间的差异。结果表明,动刚度矩阵法可以精确求解螺旋弹簧随频率变化的动刚度特性,在一阶模态振动频率后弹簧刚度值呈现103等级的剧烈变化,该结果与有限元模型结果一致;一系螺旋弹簧的动态频率特性导致轮轨激励由车轮至构架的振动位移传递率提高到接近于1,而对车体的振动传递率提高到了10-3左右;在整车车辆-轨道动力学计算中,其对轮轨振动影响较小,但车体与构架出现了较高的高频振动能量峰值。包含一系悬挂动刚度的车辆模型更接近实际,为了降低车辆振动,应尽量提高一系螺旋弹簧自振频率并降低动刚度变化幅值。

车轮踏面磨耗及轨道不平顺联合作用下的车辆-轨道系统随机分析模型

车轮磨耗和轨道不平顺具有随机特征。基于车轮圆周磨耗的概率特征及高斯分布假设,将车轮型面离散化,形成车轮型面磨耗量的概率反演方法;同时,基于轨道不平顺概率模型,实现轨道不平顺在不同幅-频状态下的遍历随机模拟。结合车辆-轨道耦合动力学理论和概率方法,建立考虑车轮踏面磨耗-轨道随机不平顺耦合作用的车辆-轨道随机分析模型,并用一类概率密度演化方程解决模型的概率密度传递问题。此模型能较好分析车辆-轨道系统在不同车轮型面磨损及线路随机不平顺联合作用下的动力响应分析及可靠度计算问题。