Theory of random energy analysis for train derailment

Three fundamental problems in the calculation of train derailment abroad and at home were pointed out and the solutions to these problems were presented. The theory of random energy analysis for train derailment was suggested. The main contents of this theory are as follows: geometric criterion of derailment; method of random energy analysis of transverse vibration of train track system; mechanism of derailment and energy increment criterion for derailment evaluation; calculation of the entire derailment course of train. This theory is used to calculate a case of freight train derailment, which corresponds to an actually occurring accident. Another derailment test, in which the train is judged not to be derailed, is calculated and the maximum vibration response is well correspond to the test results. And the effectiveness and practicability of the theory are proved by the two calculated cases.

Development of a simulation model for dynamic derailment analysis of high-speed trains

The running safety of high-speed trains has become a major concern of the current railway research with the rapid development of high-speed railways around the world.The basic safety requirement is to prevent the derailment.The root causes of the dynamic derailment of highspeed trains operating in severe environments are not easy to identify using the field tests or laboratory experiments.Numerical simulation using an advanced train–track interaction model is a highly efficient and low-cost approach to investigate the dynamic derailment behavior and mechanism of high-speed trains.This paper presents a three-dimensional dynamic model of a high-speed train coupled with a ballast track for dynamic derailment analysis.The model considers a train composed of multiple vehicles and the nonlinear inter-vehicle connections.The ballast track model consists of rails,fastenings,sleepers,ballasts,and roadbed,which are modeled by Euler beams,nonlinear spring-damper elements,equivalent ballast bodies,and continuous viscoelastic elements,in which the modal superposition method was used to reduce the order of the partial differential equations of Euler beams.The commonly used derailment safety assessment criteria around the world are embedded in the simulation model.The train–track model was then used to investigate the dynamic derailment responses of a high-speed train passing over a buckled track,in which the derailmentmechanism and train running posture during the dynamic derailment process were analyzed in detail.The effects of train and track modelling on dynamic derailment analysis were also discussed.The numerical results indicate that the train and track modelling options have a significant effect on the dynamic derailment analysis.The inter-vehicle impacts and the track flexibility and nonlinearity should be considered in the dynamic derailment simulations.

A framework for train derailment risk analysis

This study aims to develop a framework based on the Nadal formula to assess train derailment risk. Monte Carlo simulation was adopted to develop 10000 sets of random parameters to assess train derailment risk subject to the curvature radius of the track, the difference between the flange angle and the equivalent conicity, and accelerations from 250 to 989.22 gal during horizontal earthquake. The results indicated that railway in Taiwan, China has no derailment risk under normal conditions. However, when earthquakes occur, the derailment risk increases with the unloading factor which is caused by seismic force. The results also show that equivalent conicity increases derailment risk;as a result, equivalent conicity should be listed as one of maintenance priorities. In addition, among all train derailment factors, flange angle, equivalent conicity and unload factors are the most significant ones.

Energy increment criteria for evaluation of train derailment

The criteria for evaluation of train derailment were studied. The worldwide commonly used evaluation criteria for wheel derailment were summarized and their main problems were pointed out. The mechanism of train derailment was expounded on the basis of system dynamics stability concept. And the energy increment criteria were proposed to evaluate train derailment. By applying the criteria, the calculated results concerning 6 cases of freight train derailment on tangent railway line and 6 cases of freight train derailment on bridge were obtained, which are all in agreement with the practical situation. The safety, comfort and stability results concerning 3 cases of freight train running on bridge were analyzed. In addition, the running speed limits of freight train on the Yanconggou and Donggou bridge in the Beijing-Tonghua railway line of 50km/h and 60km/h, respectively, were proposed. And the running speed of freight train on the Nanjing Yangtze River Bridge can reach 70km/h.

Derailment risk and dynamics of railway vehicles in curved tracks： Analysis of the effect of failed fasteners

The effect of the fastener＇s failure in a railway track on the dynamic forces produced in the wheel-rail contact is studied using the simulation software VAMPIRE to assess the derailment risk of two different vehicles in two curves with distinct characteristics. First, a 3D-FEM model of a real track is constructed, paying special attention to fasteners, and calibrated with displacement data obtained experimentally during a train passage. This numerical model is subsequently used to determine the track vertical and lateral stiffness. This study evidences that although the track can practically lose its lateral stiffness as a consequence of the failure of 7 consecutive fasteners, the vehicle stability would not be necessarily compromised in the flawed zone. Moreover, the results reveal that the uncompensated acceleration and the distance along which the fasteners are failed play an important role in the dynamic behavior of the vehicle-track system, influencing strongly the risk of derailment.

Research on dynamical derailment system for CRH

Based on an improved three-dimensional wheel-rail contact trace algorithm and a new model of wheel-rail contact force, wheel-rail derailment dynamical model is established on China Railways High-speed（CRH） vehicle and developed in MATLAB software, which is called dynamical derailment system for CRH （DDSCRH）. Analyzed on dynamical derailment process of high speed vehicle by DDSCRH, the critical position on chmb wheel and influence factors on lateral force for derailment are obtained. Finally, high-speed vehicle dynamical simulation is verified on DDSCRH by comparing with the existing results of the line test.

Simulation on derailment base on a new wheel-rail contact method

The simulation package for special research on derailment of high speed vehicle is established.The process of derailment is different from other behaviors of vehicle dynamics because of large lateral displacement of wheelsets.To get correct results,a new fast algorithm to computing contact force is adopted and the exact geometry analysis is necessary to judge derailment happened.Variation of contact condition and coefficient of friction with speeds are also considered into vehicle-track coupled model.The structure of the package is presented in detail.The results are particular emphasis on investigation influence of maximum track defect,critical vehicle speed and various contact condition on derailment.The simulation can also be used to define the most risk factor leading to derailment.

On a New Method for Evaluation of Wheel Climb Derailment

In the paper, a new derailment index λ for evaluation of wheel climb derailment is proposed which is based on primary suspension forces. It is easy to apply because of its minimum criterion characteristic and can also be applied to explain the reason why wheel climb derailments are almost always accompanied by some wheel unloadings.

Fragility analysis for vehicle derailment on railway bridges under earthquakes

With the rapid development of high-speed railways around the globe,the safety of vehicles running on bridges during earthquakes has been paid more attention to.In the design of railway bridges,in addition to ensuring the safety of the bridge structure in earthquake,the vehicle safety should also be ensured.Previous studies have focused on the detailed analysis of vehicle derailment on bridges,proposing complex numerical algorithms for wheel-rail contact analysis as well as for parametric analysis,but they are inconvenient for designers.Intensity measure(IM)used in performance-based earthquake engineering is introduced in this study.A method to evaluate the vehicle safety on bridges under earthquakes is proposed with respect to the optimal IM.Then,the vehicle derailment case of the Kumamoto earthquake in Japan verifies the decoupling method of vehicle-bridge interaction model.In the assessment of vehicle derailments,eight IMs are systematically compared:the IMs of bridge deck motion are generally better than those of ground motion;the variation coefficient of spectral intensity of the bridge deck is the smallest at different frequencies.Finally,the derailment fragility cloud map is presented to evaluate the vehicle safety on bridges during earthquakes.

桥上脱轨列车姿态演变行为与倾覆风险研究

针对高速列车桥上脱轨后的车体姿态演变行为与倾覆风险问题,通过多体动力学方法,建立八编组整车−桥梁防护墙多体动力学模型并开展数值研究。首先,通过相同工况下多体动力学结果与有限元方法结果,对比验证本文模型的正确性。然后,通过数值模拟分别研究直线空载高速列车、直线满载高速列车、曲线不同离心加速度下高速列车脱轨后的动力学演变行为。研究结果表明:桥上脱轨列车与防护墙发生撞击后,会出现明显的车轮跳起和车体大幅度侧滚现象,各车存在极大从右后向左前翻滚到线路外侧坠落的风险;桥梁曲线脱轨比直线脱轨更加危险,会出现明显的甩尾现象,离心加速度越大,甩尾现象越明显。

不同初始姿态下城际列车车钩碰撞特性及脱轨风险分析

列车碰撞时车钩缓冲装置经常存在初始姿态偏置,影响列车运动姿态,增加脱轨风险。本文以某城际列车全自动车钩为研究对象,建立车钩非线性有限元模型,并与台车冲击试验进行对比验证,在此基础上建立城际列车头车对撞模型,研究初始位移偏置和角度偏转对车钩的碰撞特性及列车脱轨风险的影响。研究结果表明:随着初始偏置及偏转程度的增加,车钩点头角及摇头角稳定值逐渐增大,且不同初始姿态对车钩转角的影响程度不同,点头角对初始垂向偏置和点头偏转较为敏感,摇头角对初始横向偏置和摇头偏转较为敏感。此外,初始姿态对主动车的轮对抬升有重要影响,当车钩点头角随偏置及偏转增大而明显增大时,车体所受垂向力增加,转向架轮对抬升量变大,列车更易出现脱轨现象。

地铁列车脱轨防护装置方案

[目的]在自然灾害、车辆或轨道关键部件失效、外部冲击等不可预知的复杂状态下,地铁列车仍有可能会发生脱轨。因此,对列车被动脱轨防护装置方案的研究十分必要。[方法]建立地铁列车多体系统动力学非线性仿真模型,采用典型的车轮踏面外形和典型钢轨外形匹配,根据地铁列车运行的线路特点,提出地铁列车脱轨防护装置的三种方案,对其进行了低速运行条件下的脱轨工况仿真。针对仿真结果,综合考虑防二次爬轨脱轨的效果、安装部位的强度,以及脱轨后铁轨与脱轨防护装置发生碰撞而对车辆造成的损害,提出了在构架下端安装防脱轨横向止挡作为脱轨防护装置的方案。针对该地铁列车脱轨防护装置,进行了动力学仿真分析,并与无防护装置工况进行对比。[结果及结论]地铁列车脱轨防护装置具有明显的防脱轨效果,且具有一定的可行性。地铁列车脱轨防护装置动态包络线符合某地铁线路的限界要求,不会影响列车正常行驶,可以进行工程应用。

高速列车曲线通过性能分析及脱轨影响因素研究

列车往往会因为线路不平顺或自身运行状态问题发生脱轨事故,由于实际运行情况下列车以编组形式出现,因此对编组列车脱轨评价对象的筛选以及在此基础上的影响因素分析是至关重要的。在SIMPACK中建立编组列车动力学仿真模型,针对脱轨系数和轮重减载率这2种评价指标,采用数值仿真分析方法筛选典型运行状态下8编组列车在不同评价体系下的评价对象,比较轨道不平顺性、轨底坡、运行速度、曲线半径以及曲线超高这5种脱轨影响因素的变化规律,并采用全因子采样的方法对影响因素进行均匀采样,应用Sobol全局敏感性分析方法对影响列车脱轨的影响因素进行权重分析。研究结果表明:在编组列车26种不同工况下,第1节车的相同位置脱轨系数较其他车辆最大,该车前转向架前轮对的轮重减载率及其弯道内侧车轮的脱轨系数最大的情况分别占85%和81%,两者可以作为编组列车脱轨影响因素分析的目标。轨道不平顺性系数和轨底坡对于高速列车脱轨的影响较小,其变化趋势接近线性。运行速度对于高速列车运行安全性的影响最大,其次是曲线半径,然后则是曲线超高。运行速度对于列车运行产生的影响相对较大,即最容易导致列车曲线通过脱轨事故的发生,在实际运行环节中应当予以重视。

脱轨系数数字特征求解的同分布概率演化法

为探究高速铁路列车的脱轨系数统计特性,提出同分布概率演化法研究其数字特征(均值与标准差)、阈值、概率分布和服从该分布的前提条件。采用该方法求得脱轨系数均值和标准差与横、竖向轮轨力数字特征的关系;本文方法证明脱轨系数满足高斯分布的数学条件;采用Monte Carlo法对脱轨系数的数字特征进行验证,并比较不同方法的计算效率;提出采用阈值估计法求脱轨系数的阈值。基于该方法,以动车组通过3跨桥梁为例,研究不同轨道谱、列车速度和桥梁动挠度等工况下的列车脱轨系数。计算结果表明:对常用高速铁路桥梁而言,脱轨系数具有高斯特性;本文计算方法能准确地求得不同工况下列车脱轨系数的数字特征,计算效率较高;脱轨系数的尾部分布不是高斯分布,不同工况需要采用相应的阈值估计法才能达到高斯分布3σ法则的置信水平。

面向脱轨后被动安全防护的转向架结构优化

为了验证和优化列车转向架部件的脱轨后被动安全防护效果,提出基于多边形接触模型的列车脱轨后接触建模方法,并建立列车脱轨后动力学模型,模拟不同结构参数组合下的列车脱轨后运行行为。将所得横移量和结构参数组合作为反向传播神经网络模型的训练样本,拟合两者之间的非线性关系,采用基于锦标赛选择的自适应遗传算法搜索横移量最小解及其对应的参数组合。以拖车制动盘优化问题为例,运用该优化模型进行结构参数优化。研究结果表明:在100 km/h脱轨速度下,制动盘的最优结构参数组合的半径为335 mm、厚度为80 mm、安装位置为320 mm;与原设计相比,车辆脱轨后横移量减少80.2%,大幅度提高了制动盘被动安全防护能力。本文所提出的建模方法和优化模型可推广应用于其他列车结构的脱轨后被动安全防护能力优化和验证,具有较大的工程实用价值。

单轴迫导向径向机构布置方案选型

传统转向架通过小半径曲线时,导向轮对的冲角大,轮轨磨耗严重。双轴迫导向转向架能有效减小轮对冲角,但结构复杂,而单轴迫导向转向架结构相对简单且能有效减小导向轮对的冲角,提高车辆的曲线通过性能。因此,文章以某工程车为研究对象,分别建立了采用传统转向架、单轴迫导向转向架和双轴迫导向转向架的工程车动力学模型,对比其曲线通过性能。同时,考虑牵引力和双向运行的影响,综合分析评估径向机构安装位置与动力轮对分布位置对工程车曲线通过性能的影响,得出单轴迫导向径向机构与动力轮对的最佳布置方案,并对采用此种单轴迫导向转向架的工程车的稳定性和曲线通过性能进行分析。结果表明,其临界速度略低于采用传统转向架和双轴迫导向转向架的工程车;安装单轴迫导向径向机构能够有效减小轮轴横向力、脱轨系数和轮对冲角;与采用传统转向架的工程车相比,其轮轴横向力降低了9.51%,脱轨系数降低了11.32%,一位轮对冲角降低了52.49%。

地铁车辆段小号码道岔区域车辆脱轨仿真分析

[目的]小号码道岔在城市轨道交通尤其是地铁车辆段内有着较为广泛的应用,但其转辙角偏大的特征使车辆在通过道岔时存在脱轨的风险。研究地铁车辆段道岔心轨位置处车辆脱轨的原因很有必要。[方法]逐步建立轮对、转向架子模型和单节车厢模型,然后用铰接的方式将所有车厢连接形成整车模型。在道岔前方设置直线段以消除车辆起动的影响。通过线性内插得到整个道岔区域的相应轨道截面,然后导入到软件中计算。选取轮对横移量、脱轨系数和轮重减载率作为评价指标,分析了车速、车轮踏面型式、钢轨竖向刚度等因素对列车脱轨风险的影响规律。[结果及结论]由仿真分析得出如下结论:当车速过大时,轮重减载率会大幅超标,因此建议列车通过道岔时车速控制在5 km/h以内;当车轮采用LMX型踏面时,车辆会相对平稳地通过辙叉区的有害空间,有利于降低列车的脱轨风险;列车在通过钢轨竖向刚度为200 MN/m的道岔时更易发生脱轨。

城市轨道交通列车脱轨碰撞事故仿真研究

[目的]针对2015年发生的一次城市轨道交通不锈钢车体列车脱轨事故的过程进行仿真,重现在复杂事故场景中的车体破坏的直接原因和过程。[方法]在调查事故场景和不锈钢车体结构与特点的基础上,使用有限元方法重建事故模型,分析了整个事故中车辆的速度、加速度、能量变化。[结果及结论]仿真研究的结果表明,事故发生时的巨大能量和地面的高低起伏,导致中间车辆发生爬车、蛇行及相互碰撞,是造成本次事故中不锈钢车体结构发生断裂失效的重要原因。车体断裂位置主要集中在驾驶室框架与底架、端墙与顶棚、底架与侧墙和端墙的连接处。

基于特征物理量的铁道车辆脱轨检测技术研究

近年来,铁道车辆迅速发展,但伴随着的安全问题也愈发引起的社会关注,其中脱轨问题毋庸置疑成为人们关注的焦点,所以对于铁道车辆的脱轨检测技术的研究具有重大意义。经过长时间的探索研究,前人使用经典的脱轨系数、轮重减载率等指标判断铁道车辆是否面临脱轨风险时,存在日常运营车辆的轮轨力难以检测、信息传递滞后等问题。针对以上问题,本文首先进行铁道车辆脱轨模拟仿真实验,确定轮对脱轨失效显著且易测的脱轨特征物理量即轮对横向加速度和侧倾角;其次,使用复合传感器检测仿真模拟时的轮对运行状态,通过实时检测车辆运行时轮对的状态,从而设计出一种脱轨的在线检测方案;然后,基于铁道车辆脱轨模拟仿真实验,分析铁道车辆行驶在直线与曲线工况下的轮对脱轨时对应的观测量阈值,并对车辆行驶在曲线路段设置的超高所引入的额外侧倾角进行补偿;最后,根据脱轨检测方案设计一套脱轨检测与预警系统,采用仿真算例来验证设计方案的可行性与有效性。研究结果表明:设计的脱轨检测技术方案可实现对车辆脱轨故障的有效检测,能有效支撑脱轨预警系统的开发,达到保护乘客和车辆安全的目的。此研究对于铁道车辆的快速安全发展具有一定的价值,为铁道车辆的脱轨检测技术的研究提供了更多思路。

基于Simpack转向架的适配性改进及仿真试验分析

转向架可有效解决传统矿山铁路运输时需卸车—装车—再发车而导致的运输效率低和货损率大的问题,为进一步提升转向架的适配性,需要结合实际运输条件对其进行改进。以E22型转向架为研究对象,基于Simpack软件构建了改进后转向架的模型,并根据相关规范设定了判定标准,重点对转向架在不同工况条件下的轮重减载率、脱轨系数以及轮轴横向力进行仿真分析;结合实践工况对不同工况条件下的脱轨系数和轮重减载率进行试验分析。上述两项结论均满足相关标准要求,可在实际中推广应用。