铁路车辆/轨道耦合系统在竖向冲击载荷作用下动态响应的计算机模拟研究

车辆与轨道的动态相互作用,是铁路轮轨接触式运输系统中最基本的问题之一,它直接制约着铁路运营速度的提高和运载重量的增加,也影响着铁路安全运行。本文采用有限元方法,对我国C61型运煤货车,按照车辆/轨道系统的实际几何形状、材料性质和边界条件建立了包括车辆和轨道系统的有限元模型,应用大型非线性动力分析程序LS-DYNA3D来模拟车辆通过轨道错牙接头时的轮/轨动态响应过程。计算结果表明车轮和轨道之间的竖向动态接触力大约是静轮载的2倍,与已有的现场试验结果基本吻合。因此应用有限元方法研究车辆/轨道耦合系统是可行和可靠的。     

高频轮轨相互作用下钢轨的波磨

对高频轮轨相互作用下轨道的波浪形磨损问题进行了考察．通过引入轮轨的灵感度，得到了轮轨间蠕滑力的波动同轨道表面不平顺幅值和表面曲率的波动关系；通过引入摩擦功计算了轨道表面的磨损，得到了磨损率的计算公式．结果表明，钢轨的磨损率同轨道的垂向动力行为密切相关；在不同激振频率下轨道表面不同点的磨损率不同．     

铁路轨道阻尼比容的实测与分析

铁路机车、车辆沿轨道高速运行时,由于机车、车辆和轨道的相互作用,二者作复杂的振动。多年来,人们对铁路轨道的振动,进行过不少的研究工作,其中轨道振动阻尼是人们关心的重要问题之一。以往,对轨道的振动阻尼往...     

轨下支承失效对直线轨道动态响应的影响

建立了基于Timoshenko梁模型的车辆/轨道耦合动力学模型,分析轨下支承失效对直线轨道动态响应的影响. 钢轨被视为连续弹性离散点支承上的无限长Timoshenko梁,通过假设轨道系统刚度沿纵向分布发生突变来模拟轨下支承失效状态. 推导了考虑钢轨横向、垂向和扭转运动的轮轨滚动接触蠕滑率计算公式. 利用Hertz法向接触理论和沈氏蠕滑理论计算轮轨法向力及轮轨滚动接触蠕滑力. 采用移动轨下支承模型的车辆/轨道耦合系统激振模式,考虑轨枕离散支承对系统动力响应的影响. 通过新型显式积分法求解车辆/轨道耦合动力学系统运动方程,由数值分析计算得到不同轨下支承失效状态下直线轨道的动态响应. 结果表明,轨下支承失效对直线轨道变形及加速度有显著的影响,随着失效轨下支承个数的增加,轮轨相互作用力和轨道部件的位移、加速度将会急剧增大,将加速失效区段线路状况的恶化.      

复杂机车振动环境下牵引电机轴承服役寿命评估

牵引电机是铁路机车的动力源, 其关键零部件(支承轴承等)的服役性能直接影响机车传动系统的稳定性和可靠性. 对于重载机车, 传统轴承服役寿命评估方法主要基于定载荷工况, 难以准确评估轨道不平顺等复杂外部激励作用下电机轴承的服役寿命. 因此, 本文根据车辆-轨道耦合动力学理论, 考虑轨道车辆运行过程中的轮轨相互作用和齿轮啮合作用, 建立了具有牵引动力传动系统的机车-轨道耦合动力学模型; 采用线性损伤累积准则和ISO 281标准计算方法, 评估了复杂机车振动环境下牵引电机轴承的服役寿命. 结果表明, 在轨道随机不平顺激励下, 机车轮轨垂向力、齿轮啮合力、牵引电机内部转子离心力、不平衡磁拉力等明显增大; 在复杂机车振动环境中, 电机轴承内部滚子-滚道相互作用加剧, 传动端与非传动端轴承的疲劳寿命缩短; 随着线路状态的不断恶化和机车运行速度的提高, 牵引电机轴承的预测寿命里程不断减小; 由于传动端轴承承受较大的外部动态载荷, 传动端轴承的服役寿命明显低于非传动端轴承. 本文提出的评估方法可为机车牵引电机轴承的设计、选型和寿命评估提供理论指导.      

基于高频轮轨作用的波浪型磨损研究

对高频轮轨相互作用下轨道的波浪形磨损问题进行了考察。通过引入轮轨的灵敏度，得到了轮轨间蠕滑力的波动同轨道表面不平顺幅值和表面曲率的波动关系；通过引入摩擦功计算了轨道表面的磨损，得到了磨损率的计算公式。结果表明，钢轨的磨损率同轨道的垂向动力行为密切相关；轨道表面不同点在不同激振频率下的磨损率不同。     

轮轨滚动接触力学的发展

轮轨滚动接触力学主要研究轮轨滚动接触过程中的作用行为。由于其研究的复杂性,目前在该领域的研究已基本形成既独立又关联的六个分支,它们分别是轮轨滚动接触蠕滑率/力理论、轮轨粘着、接触表面波浪形磨损、轮轨滚动疲劳、脱轨和轮轨噪音。本文综述了这几个方面研究的发展历史和现状。由于轮轨滚动接触作用的研究又是以轮轨滚动接触蠕滑率/力理论为基础的,故本文着重评述目前常用于车辆/轨道动力学和轮轨关系研究中几个经典滚动接触理论模型的优缺点。根据实际工程中轮轨作用存在的严重问题,并提出轮轨滚动接触理论及其试验在今后的研究方向和所要考虑的有关重要因素。      

基于有限元法的轮轨蠕滑特性研究

轮轨滚动接触蠕滑率／力理论是轮轨相互作用一系列问题研究的基础．现有的几种计算蠕滑力的理论模型均建立在Hertz接触条件和半空间假设的基础上，已经无法完成对复杂的接触问题的进一步研究．使用有限元参数二次规划法来求解轮轨的三维弹性／弹塑性接触问题，得出了在不同的轴重、牵引力矩、摩擦系数、踏面形状、横向力条件下的轮轨接触力．提出用轮轨接触的轮周位移计算蠕滑率的新方法，并对在各种参数下所得到的蠕滑率进行了分析比较．     

基于逆虚拟激励法的垂向轨道不平顺功率谱识别

提出一种识别轨道垂向不平顺功率谱的新方法.采用定点激励的垂向车辆-板式轨道耦合动力学模型.车辆简化为多刚体模型,板式轨道考虑为3层梁模型,并通过线性轮轨力耦合车辆模型和轨道模型.以轴箱加速度作为测量对象,采用逆虚拟激励法识别垂向轨道不平顺的功率谱,并研究了测量误差和车辆运行速度对垂向轨道不平顺的识别精度的影响.数值结果表明,本文方法能够较为准确地识别垂向轨道不平顺功率谱,为列车运行环境载荷识别与评估提供了新的途径.     

基于对称性的三维车辆轨道耦合系统随机振动虚拟激励方法

基于结构的对称性提出了用于三维车辆轨道耦合系统高效随机动力响应分析的虚拟激励方法.车辆采用刚体动力学模型,轨道结构利用三维轨道广义单元建模,车辆与轨道通过线性轮轨关系耦合.采用虚拟激励法将高低、方向和水平三类轨道不平顺转化为一系列筒谐的虚拟不平顺;考虑车辆及轨道结构的对称性,分别推导了耦合系统的对称和反对称凝聚矩阵,提出了用于车辆轨道耦合系统动力响应计算的自由度凝聚方法,将耦合系统的自由度缩减至原来的一半以下,并在此基础上实现了耦合系统随机振动的高效分析.数值算例将本文方法与传统有限元方法进行对比,验证了本文方法的正确性和有效性.     

铁路轮轨冲击振动模拟与试验

对铁路工程领域普遍存在的轮冲击振动现象进行了理论与试验研究。将车辆模拟为移动的多刚体振动系统,将轨道描述成离散点支承连续梁结构,应用快速数值 发方法编制了ＶＩＣＴ模拟软件,实现了轮轨冲击振动的快速数值模拟。     

Experimental Investigation on Dynamic Railway Sleeper/Ballast Interaction

In ballasted railway tracks, one of the important components that supports the rails and distributes wheel/rail loading onto the ballast supporting formation is a railway sleeper (sometimes is also called a “railway tie”). This paper presents results of an experimental modal analysis of prestressed concrete sleepers in both free-free and in-situ conditions, incorporating the dynamic influence of sleeper/ballast interaction. Dynamic interaction between concrete sleepers and ballast support is crucial for the development of a dynamic model of railway track capable of predicting its responses to impact loads due to wheel flats, wheel burns, irregularities of the rail, etc. In this study, four types of prestressed concrete sleepers were in-kind provided by the Australian manufacturers. The concrete sleepers were tested using an impact hammer excitation technique over the frequency range of interest, 0–1600 Hz. Frequency response functions (FRFs) were measured using PULSE modal testing system. The FRFs were processed using STAR modal analysis package to identify natural frequencies and the corresponding mode shapes for the sleepers. The conclusions are presented about the effect of the sleeper/ballast interaction on the dynamic properties of prestressed concrete sleepers and their use for predicting railway track dynamic responses.     

Interaction between a moving two-mass oscillator and an infinite homogeneous structure: Green’s functions method

This paper deals with the interaction between a vehicle and a slab track using the model of moving wheel for both frequency and time-domain. The vehicle is reduced to a moving two-mass oscillator and the slab track is considered as an infinite structure consisting of elastically supported double Euler–Bernoulli beams. In order to perform the time-domain analysis, a semi-analytical method based on the outstanding properties of the time-domain Green’s functions of the slab track has been developed. The method allows the computing of the non-linear wheel/rail contact (the contact loss and the non-linear contact stiffness). The vehicle/track interaction due to the polygonal wheel and the corrugated rail has been investigated and the running velocity and non-linear wheel/rail contact influences have been pointed out.     

车-桥-线竖平面振动及其能量转化机制精细建模

建立了考虑车-桥(线)纵向振动及其能量相互转化机制的竖平面内精细耦合运动方程.将车-桥(线)视为一个整体系统,车辆各剐体的纵向运动均作为独立的自由度,考虑到车-桥(线)纵向振动及其能量相互转化机制,车辆驱动或制动作用采用轮轨间的纵向相互作用力和轮对作用力矩模拟,桥梁、线路结构采用梁单元离散,线路与桥梁之间的钢轨基础采用竖向和纵向的均布弹簧阻尼连接,建立了竖平面内精细耦合运动方程,它可合理模拟车桥(线)间能量相互转化的过程.简支梁桥算例表明:车辆在桥上无驱动或制动运行过程中,不考虑轨道结构时车速先增加后减小,而考虑轨道结构时车速只有减小的趋势,轮对还发生了高频的纵向振动,且车体和轮对的纵向振动对轨道竖向不平顺较为敏感;此外,考虑轮轨滚动碾压作用和能量转化机制时,钢轨加速度响应略偏大.本文研究可为实际车辆动态变速运行的模拟和更精细空间耦合模型的建立提供研究基础.     

A novel method to estimate derailment probability due to track geometric irregularities using reliability techniques and advanced simulation methods

Track irregularities have a dramatic impact on the response and vibration of a railway vehicle and on the interaction between wheel and rail. The random nature of the track structure and constituent materials and the effects of other factors such as maintenance conditions and transit traffic give rise to the random nature of track irregularities. This research provides a method to estimate the derailment probability of a railway vehicle where track irregularities are assumed to be random, and the interaction of the track and the moving train is considered using advanced dynamic analysis. For this purpose, the limit state function of derailment was estimated using the response surface method and advanced simulation. The probability of derailment was then estimated using a Level 3 reliability method.     

An Alternative Rail Pad Tester for Measuring Dynamic Properties of Rail Pads Under Large Preloads

One of the main components in ballasted railway track systems is the rail pad. It is installed between the rail and the sleeper to attenuate wheel/rail interaction loads, preventing the underlying railway sleepers from excessive stress waves. Generally, the dynamic design of tracks relies on the available data, which are mostly focused on the structural condition at a specific toe load. Recent findings show that track irregularities could significantly amplify the loads on railway tracks. This phenomenon gives rise to a concern that the rail pads may experience higher effective preloading than anticipated in the past. On this ground, this paper highlights the significance of accounting for effects of preloading on dynamic properties of polymeric rail pads. An innovative test rig for controlling preloads on rail pads has been devised. A non-destructive methodology for evaluating and monitoring the dynamic properties of the rail pads has been developed based on an instrumented hammer impact technique and an equivalent single degree-of-freedom system approximation. Based on the impact-excitation responses, some of the selected rail pads have been tested to determine such modal parameters as dynamic stiffness and damping constants in the laboratory. The influence of large preloads on dynamic properties of both new and worn rail pads is demonstrated in this paper. Additionally, the design criteria, which has been used to take into account the influence of the level of preload on dynamic properties of generic rail pads, are discussed. Note: The authors’ work in the references can be found electronically via UoW Research Online at URL