An investigation into the effect of train curving on wear and contact stresses of wheel and rail

Some important papers concerning the studies on rail wear and wheel/rail contact stresses are briefly reviewed. The present paper utilizes a numerical method to analyze the effect of railway vehicle curving on the wear and contact stresses of wheel/rail. The numerical method considers a combination of Kalker's non-Hertzian rolling contact theory, a material wear model and a vertical and lateral coupling dynamics model of the vehicle/track. In the analysis, the important factors influencing on the wear and the contact stresses are, respectively, the curving speed, the curved track super-elevation and the rail cant. Compared to the present model, some concerned models and results in the published papers are in detail discussed. Through the detailed numerical analysis, it is found that the difference between the normal loads of the left and right of the wheelset increases linearly with increasing the vehicle curving speed. The material wear volume per length along the rail running surface has a tendency to grow. However, the variation of the maximum normal contact stress has a large fluctuation as the curving speed increases. The increase of the maximum contact stress depends greatly on not only the normal load but also the profiles of the wheel/rail. Increasing the track super elevation efficiently lowers the normal load difference of the left and right of the front wheelset, and the contact stresses and the wear. The rail cant has a great influence on the low rail wear of the curve track. An increase in rail cant results in a great increase in the low rail wear of the curved track, and a decrease in the outside rail wear. These conclusions are very useful in the maintenance of the track.     

基于轮轨噪声检测的列车接近报警研究

建立了轮轨激励振动的数学模型,通过Euler梁近似和降阶处理求解,得到了长钢轨的各阶固有频率;对现场采集的钢轨振动信号进行分析,发现明显存在钢轨的某些阶次特征频率分量,且这些分量的能量在列车距离传感器1000m以内时有逐渐增大的趋势.     

新型高速轮轨接触疲劳试验机研制

220 kW新型高速轮轨疲劳试验机可准确再现时速300 km/h条件下,轮轨滚动接触时的疲劳、钢轨波磨和侧磨等现象,模仿真实工况条件下高速轮轨损伤机理及粘着特性等,为高速铁路发展建设提供必要的研究手段和设计数据。     

曲线半径及轴重对轮轨摩擦功影响的研究

基于非Hertz滚动接触理论利用数值计算方法详细分析了静态接触情况下,轴重和曲线半径对轮轨接触质点间等效应力、接触斑粘滑区的分布、总滑动量和摩擦功的影响。分析计算表明,轴重增加引起轮轨接触质点间等效应力,接触质点间粘滑区的面积以及总滑动量的变化,同时对轮轨接触质点阍的摩擦功的变化有重要影响;小曲线半径处轮轨接触质点间的总滑动量,接触斑滑移区的面积以及摩擦功都明显增大,导致曲线上钢轨磨损加剧。因此曲线半径和轴重是影响轮轨滚动接触磨损的重要因素。     

基于向量式分析的轮轨接触模拟

介绍了一种新的区别于传统有限元方法的计算力学方法——向量式分析方法。在理论公式推导的基础上,通过自编程序,利用该方法对轮轨静态接触问题进行了模拟。计算结果表明,该方法得到的最大轮轨法向接触压力、接触斑大小、Von mises等效应力与Hertz接触理论和有限元软件ANSYS结果仅相差±5%,吻合很好。向量式分析方法具有有效处理连续体大转动的优点,可为进一步模拟高速轮轨滚动接触动态行为提供很好的借鉴。     

多刚体系统运动学分析的自然坐标法及在悬架运动学分析中的应用

本文介绍了一种适用于计算机分析的多刚体系统运动学分析的自然坐标法。利用自然坐标描述多刚体系统时,只需要一些点和一些单位向量,刚体的约束方程和运动副的约束方程组成了多刚体系统的运动学约束方程。约束方程均为线性或二次方程,因此求解方便。文中利用该方法分析了Maepherson悬架的轮胎横向滑移量、主倾内倾角等与车轮上、下跳动距离的关系。     

Numerical analysis of rolling-sliding contact with the frictional heat in rail

Thermal damage caused by frictional heat of rolling-sliding contact is one of the most important failure forms of wheel and rail. Many studies of wheel-rail frictional heating have been devoted to the temperature field, but few literatures focus on wheel-rail thermal stress caused by frictional heating. However, the wheel-rail creepage is one of important influencing factors of the thermal stress In this paper, a thermo-mechanical coupling model of wheel-rail rolling-sliding contact is developed using thermo-elasto-plastic finite element method. The effect of the wheel-rail elastic creepage on the distribution of heat flux is investigated using the numerical model in which the temperature-dependent material properties are taken into consideration. The moving wheel-rail contact force and the frictional heating are used to simulate the wheel rolling on the rail. The effect of the creepage on the temperature rise, thermal strain, residual stress and residual strain under wheel-rail sliding-rolling contact are investigated. The investigation results show that the thermally affected zone exists mainly in a very thin layer of material near the rail contact surface during the rolling-sliding contact. Both the temperature and thermal strain of rail increase with increasing creepage. The residual stresses induced by the frictional heat in the surface layer of rail appear to be tensile. When the creepage is large, the frictional heat has a significant influence on the residual stresses and residual strains of rail. This paper develops a thermo-meehanical coupling model of wheel-rail rolling-sliding contact, and the obtained results can help to understand the mechanism of wheel/rail frictional thermal fatigue.     

往复式穿梭车在AS/RS系统中的调度分析

结合实际应用建立穿梭车的作业模型,分别对单车单工位系统、单车双工位系统、双车及多车系统流程进行了分析研究,对比其优劣,为进一步提升分配车系统的效率奠定了基础。     

水下高速航行器壳体联结强度分析

随着超空化技术被用于水下航行器减阻提速,水下高速舷行器的结构设计也成为热点.为了确保在设计范围内航行器可以正常运行,采用分析软件ANSYS对水下高速舷行器壳体的卡箍连接强度进行了研究.考虑到实际问题的复杂性,首先建立了整个壳体的三维有限元模型,初步分析了壳体应力的大致分布;然后利用子模型技术以及非线性有限元技术,建立了壳体卡箍连接部位的有限元子模型,进一步分析了壳体间连接的接触强度.以有限的计算机资源,得到较为准确的结果.分析结果表明在常态下壳体结构联结强度较好,并进一步预估了壳体的极限载荷.为航行器壳体的结构设计以及优化提供了理论依据.     

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 loco-motive 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 multi-cut 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.     

异形高耸塔机回转支承的接触动力学分析

基于刚性多体接触动力学理论,运用三维建模软件Pro/E和动力学仿真软件ADAMS,对异形高耸塔机的回转支承进行接触动力学分析研究,分别以Restitution - based模型和Impact函数模型对其接触过程进行仿真,得出各回转位置角处的接触力和变形量,并与理论计算值相比较,为接触分析模型的选择及回转支承的优化设计与强度校核提供了依据.     

The influence of surface roughness and the contact pressure distribution on friction in rolling/sliding contacts

A numerical contact model is used to study the influence of surface roughness and the pressure distribution on the frictional behaviour in rolling/sliding contacts. Double-crowned roller surfaces are measured and used as input for the contact analysis. The contact pressure distribution is calculated for dry static contacts and the results are compared with friction measurements in a lubricated rolling/sliding contact made with a rough friction test rig. The mean pressure is suggested as a parameter that can be used to predict the influence of surface roughness on the friction coefficient in such contacts. The results show two important properties of the friction coefficient for the friction regime studied in this paper: (1) there is a linear decrease in friction coefficient as a function of the slide-to-roll ratio, and (2) the friction coefficient increases linearly with increasing mean contact pressure up to a maximum limit above which the friction coefficient is constant. The absolute deviation of experimental results from the derived theory is for most cases within 0.005.     

Rolling cylinder on an elastic half-plane with harmonic oscillations in normal force and rotational speed. Part I: Solution of the partial slip contact problem

We study the effect of harmonic oscillations during the steady rolling of a cylinder on a plane in partial slip contact conditions in the limit of small oscillations. The solution is an extension of that given in Barber et al. [1] for infinitely large coefficient of friction. Here, the effect of varying normal load and hence contact area is investigated in detail by analyzing the first order variation of the tangential force and the corresponding relative displacements.In particular, the solution is given in terms of an explicit length scale d in the Flamant solution used as a Green function. Appropriate choice of values of d allows to treat both two-dimensional problems and three-dimensional ones having elliptical contact area sufficiently elongated in the direction of the rotation axis.Also, this analysis can be used as starting point for corrugation calculations in railway tracks, where oscillations in time of the normal forces can result in non-uniform wear and hence in amplification of the corrugation.     

水油介质下研磨子对轮轨增黏与损伤影响

利用滚动磨损试验机开展轮轨黏着试验,研究水油介质下研磨子对轮轨增黏与损伤行为的影响。结果表明:水油介质下研磨子具有明显轮轨增黏作用,其增黏效果随施加压力的增加而增大,相同压力作用时油介质下研磨子的轮轨增黏效果更佳;水油介质下施加研磨子会加重轮轨试样的磨损,随压力增加轮轨试样磨损量呈增加趋势;水油介质下研磨子对轮轨试样表面损伤具有较大影响作用,增加压力会加重轮轨试样的表面损伤和塑性流动;随施加压力增加,水介质下轮轨试样损伤从轻微磨损向明显的表面剥离损伤转变,油介质下轮轨试样损伤从轻微点蚀转变为明显的表面疲劳损伤。     

电动汽车再生制动系统双向DC/DC变换器的设计

为了实现电动汽车再生制动的能量回收方案,采用超级电容作为储能元件,设计了电动汽车超级电容再生制动系统双向DC/DC变换器,介绍了DC/DC变换器主电路的四种控制方案。实验测试证明了设计合理,工作稳定可靠。     

基于Pro／E的桥梁检测车三维建模与运动仿真

桥梁检测车是检测桥梁的重要检测工具。为了了解桥梁检测车的结构组成及检测臂的工作过程,用Pro／E3．0的实体建模功能对检测车各个结构进行了三维建模,同时对建立的零件模型进行了虚拟装配及装配体干涉检查;在Pro／E的运动仿真模块中对检测车检测桁架的工作过程进行了运动仿真。从建立的模型中可以直观的了解到检测车主要结构的连接关系;而运动仿真结果则直观的显示了检测车的实际工作过程,对桥梁检测车的结构设计及装配具有参考意义。     

Hertz理论与有限元法分析轮轨接触疲劳的差异性研究

采用Hertz理论和有限元分析软件ANSYS,对钢轨表面存在微裂纹的轮轨接触疲劳问题进行研究,在不同轴重和运行状态下,获得不同位置的裂纹尖端应力强度因子。结果表明,随着轴重的增加,应力强度因子KI增加,而KII的变化趋势因车轮运行状态的不同而不尽相同。摩擦力的存在,使得KI、KII明显增加,且明显改变KII的变化趋势;在无摩擦力时,KII所占KI的比例约为6%,纯滚动时,KII所占KI的比例达到将近20%,全滑动时,KII所占KI的比例接近50%,因此,对钢轨进行疲劳断裂机理分析时,KII明显不可忽略。由于Hertz理论不考虑材料的塑性和轮轨间的摩擦力,使得Hertz理论分析轮轨接触疲劳时有适用范围小、计算结果偏大、误差累计等缺点,而有限元法是解决复杂轮轨接触疲劳问题更有效的方法。     

The effect of tape overwrap angle and head radius on head/tape spacing and contact pressure in linear tape recording

Linear tape recording devices typically employ contact recording to minimize head/media magnetic spacing and thus maximize recording density. Successful contact recording is a delicate balance between spacing and contact pressure. If an air bearing develops, spacing will exceed the 100 nm upper limit for current high recording density devices. Conversely, high contact pressure can lead to head wear or tape damage. Most recording heads produced today for linear tape devices consist of one or more cylindrical wafer sections that are bonded together to form a rigid structure. Each individual tape bearing surface is cylindrical with straight edges. The tape is held over the head contact surface by tape guides so that the tape is wrapped sharply around the edges where cylindrical surface and flat surface meet. Overwrap angle is defined as the angle between the tape after it leaves the head and a tangent to the cylindrical head surface at the edge where cylindrical surface and flat surface meet. This paper will use one-dimensional finite element modeling to explore how overwrap angle and bump radius affect head/tape spacing and contact pressure. The effects of tape stiffness, tape tension, and tape velocity will be investigated. Feasible combinations of overwrap angle and bump radius will be presented which minimize head/tape separation, yet keep contact pressure within bounds.     

轨道交通车辆门远程监测车载网关的设计与实现

为了满足监测轨道交通车辆门状态的需求,基于3G/4G移动通信平台、短距离无线通信技术设计并实现了轨道交通车辆门远程监测车载网关.车载网关以Cortex-A8架构的AM335X处理器为核心,采用嵌入式Linux操作系统,以高可靠性和灵活性完成对轨道车辆门状态参数的采集和实时传输、设备的远程维护与升级等功能.在多条轨道交通车辆上的应用表明,所设计的车载网关具有运行稳定、性能优良等特点.     

臂式斗轮堆取料机俯仰机构运动特性分析及调速回路选用

通过臂式斗轮堆取料机俯仰机构运动特性分析,绘制出液压缸速度变化曲线,进而分析液压系统主参数(流量)变化规律及设计原则,结合俯仰机构载荷特点分析流量控制即调速回路的类型及选用原则.