【作者】 郭俊；

【导师】 刘启跃；

【作者基本信息】 西南交通大学 ， 城市轨道交通技术与装备， 2006， 博士

【摘要】 随着列车速度的提高和轴重的加大，铁路运输向科学研究提出一系列挑战，许多关键科学技术问题急需解决，其中轮轨滚动接触疲劳损伤就是最复杂问题之一，它的解决对列车安全运营和降低运输成本以及发展高速列车具有重要的意义。本文在详细论述轮轨滚动接触疲劳破坏现象分类及其研究历史与现状的基础上，主要以轮轨制动损伤、轮轨冲击损伤、轮轨磨损和高速线路钢轨斜裂纹等几种典型破坏现象为研究对象，以机车车辆—轨道耦合动力学、轮轨滚动接触理论、材料摩擦磨损模型、传热学、弹塑性力学和有限元方法为基础，应用数值仿真和试验方法来研究以上几种常见损伤产生和发展的机理和关键影响因素，并提出具体的损伤预防和减缓措施。具体来说，本文主要开展了以下几方面的研究工作。采用有限元法从摩擦引起的热效应角度来探寻轮轨表面破坏的原因，建立了轮轨热—机械载荷耦合接触模型，分析制动工况即纯滑动接触过程中轮轨温升以及热应力，模型中考虑了轮轨间非稳态热传导、与环境的热对流和热辐射以及轮轨间的接触计算，研究了滑动接触过程中应力场的分布特点以及速度的影响。研究表明，轮轨间摩擦热响应的影响深度很浅(大约2mm以下)，且随着深度增加而变小；热载荷加大了轮轨表层材料的应力水平；相对滑动速度越大，轮轨热响应越明显。建立了钢轨错牙接头处三维动态弹塑性接触有限元模型，模型中考虑车轮与钢轨、钢轨与夹板、夹板与螺栓和螺栓与钢轨之间的接触。研究列车速度、轴重和错牙接头高度差对钢轨轨头处应力和应变的影响。结果表明，当车轮通过钢轨错牙接头时，车轮对钢轨的冲击作用强烈，容易导致轨端产生压溃和碎裂等损伤。车速和错牙高度对钢轨应力和应变的影响比轴重大。详细分析了轮轨作用力与钢轨斜裂纹的关系。建立了适合于广深线机车车辆—轨道空间耦合模型，进行机车车辆曲线通过动力学分析，从轮轨动态接触点和作用力大小及方向确定引起钢轨斜裂纹的机车车辆类型。还分析了京广线直线段钢轨焊接不平顺对钢轨斜裂纹的影响。理论分析发现，“蓝剑”动车组动车和SS8机车对钢轨斜裂纹形成和发展的影响最大。通过测量和分析列车通过发生钢轨斜裂纹区段时钢轨的变形和变形方向，判断轮对和钢轨作用特点，验证了理论计算结果的可靠性。通过大量的动力学仿真计算，对比分析不同超高、轨底坡、曲线半径、轨距和轨下垫层刚度情况下的轮轨作用力和轮轨接触点位置，得到了轨道结构参数的优化结果。分析计算结果为现场部门预防和减缓钢轨斜裂纹形成和扩展提供理论指导和参考。采用数值方法研究车辆曲线通过对钢轨磨损和接触应力的影响，该方法综合考虑了Kalker三维非赫兹滚动接触理论、材料磨损模型、车辆—轨道垂横向耦合动力学模型和轮轨接触几何计算，可以同时预测同一转向架四个车轮下的钢轨磨损。研究表明，改进轮轨型面是减小接触应力的主要方法；增大曲线轨道的超高能改善车辆曲线通过性能，减小接触应力和钢轨磨损；轨底坡对钢轨磨损和接触应力有显著的影响。建立了轮轨三维弹塑性滚动接触计算模型。针对广深线发生钢轨斜裂纹区段运行情况，分析不同硬度钢轨接触表面附近材料残余应力分布和塑性流动的大小和方向，由此判断钢轨滚动接触疲劳裂纹萌生的位置和方向。利用Kalker三维非赫兹滚动接触理论及其数值程序CONTACT研究轨底坡、轨距和曲线半径等轨道结构参数对轮轨静态接触应力的影响。计算结果发现，与轨距和曲线半径相比，轨底坡对轮轨接触应力的影响较大。数值结果对我国铁路轨道结构的优化设计提供了有力的参考依据。综述了各种钢轨打磨方法的原理和作用。通过对广深线路的运营特点和损伤类型分析，提出了广深线使用预防性打磨和曲线轨头非对称打磨两种打磨方法。根据线路钢轨表面裂纹出现的时间及通过的年运量情况，建议广深线曲线钢轨预防性打磨周期为6个月。钢轨曲线非对称打磨可以使接触点在轨面上向中心移动，避免接触点靠近轨肩位置，降低轮轨之间的接触应力，从而减轻斜裂纹的发生。更多还原

【Abstract】 With increases of train speed and axle load, railway transportation put forward a series of challenges to science and research. Many key problems of science and technology need to be urgently solved. Wheel-rail rolling contact fatigue and damage is one of the most serious problems. The solution to the problem is very important to the train running safety, decreasing of the transportation cost and developing high speed train.Firstly the classes of wheel-rail rolling contact fatigue and the studies on it in the past and now in the world are reviewed in detail. Based on the vehicle-track coupling dynamics theory, wheel-rail rolling contact theory, material wear model, heat transfer, plasiticity theory and finite element method, the initiation and development mechanisms and key impacting factors of some typical phenomena of wheel-rail rolling contact fatigue, such as wheel-rail braking damage, impact damage, wear and rail oblique crack, are investigated numerically and by experiment. Many measures are put forward to preventing and lightening the above damages. The main research and results are given as follows.Temperature rise and thermal stress due to wheel/rail friction play an important role in the failure of wear, flatting and checking. In this thesis, a thermal-mechanical coupling contact model of wheel/rail in sliding contact or braking is put forward to calculate the temperature rise and thermal stress with finite element method. The non-steady heat conduction between the contacting surfaces of the wheel/rail, heat-convection and radiation between the wheel/rail and an ambient are taken into consideration. The contact pressure distribution is gotten by contact element method. The numerical results show that the contact element method is effective. The thermal effects only exist in the thin layer of wheel/rail, and its effect decreases as the depth increases. The total stress levels near wheel-rail surfaces become larger due to the thermal load. Higher sliding speed leads to stronger thermal effects.A three dimensional dynamic elastic-plastic finite element model of the traditional rail joint with height difference is established, which considers the contacting interactions between the wheel and the rails, the rails and the joint bars, the joint bars and the bolts, the bolts and the rails. The influences of train speed, axle load and height difference of rail joint on the contact stresses and strains at rail head are investigated. The results obtained show that when the wheel rolls over the joint rails with height difference, the impact action between the wheel and rails is strong, which easily causes crushing and crack of rail head. The train speed and height difference have greater effect on rail stresses and strains than the axle load does.The thesis detailedly analyzes the relation between the wheel-rail contact traction and rail oblique crack. Spatial coupling dynamics models of rolling stock and track for Guang-Shen Line are established. The rolling stock types causing rail oblique crack are determined on the basis of the location of wheel-rail contact point and the magnitude and direction of the contact traction obtained from the vehicle curving dynamic analysis. The effect of rail weld irregularity in Jing-Guang Line on rail oblique is also studied. The numerical results show that Blue-Arrow power car and "SS8" locomotive car play the most important role in the initiation and evolution of rail oblique crack. The theory results are validated by experiments in which the displacement and its direction are measured when the trains pass through the tracks with rail oblique cracks. Through investigating the influences of curved track super-elevation, rail cant, curve radius, rail gauge and railpad stiffness on wheel-rail contact force and location, the optimal results of track structure parameters are obtained. The results provide theoretic basis and guidance for preventing and lightening the formation and development of rail oblique crack.The present thesis 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, a vertical and lateral coupling dynamics model of the vehicle and the curved track and the three-dimensional contact geometry analysis of wheel-rail. The developed numerical program can consider a feedback process between the rail wear and the transient coupling dynamics of four wheels of a same bogie and the track. Through the detailed numerical analysis, it is found that the difference between the normal loads of the left and right wheels 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 maximum normal contact stress fluctuates largely with the increasing curving speed. The increase of the maximum contact stress depends greatly not only on the normal load but also on the profiles of the wheel/rail. Increasing the track super elevation efficiently lowers the normal load difference between the left and right wheels of the wheelset, the contact stresses and the wear. Increasing the rail cant leads to the great growth of the low rail wear of the curved track, the reduction in the outside rail wear. The results are very useful in the maintenance of the track.A three-dimensional elastic-plastic stress analysis model for wheel-rail rolling contact is established. The model is applied to a case study of a section of Guang-Shen Line with rail oblique crack. Under the condition of different rail hardness, the residual stresses distributions and the magnitude and direction of the material plastic deformation are calculated. Besides, the effects of rail cant, rail gauge and curve radius on the static contact stresses of wheel-rail are investigated using Kalker’s non-Hertzian rolling contact theory and its numerical program CONTACT. It is found that the rail cant has a greater effect on static contact stresses of wheel-rail than rail gauge and curve radius. The results provide a powerful tool for the optimal design of track structure.The princible and function of many types of rail grinding techniques are stated. Through the analysis of the operation character and damage type of Guang-Shen Line, the thesis introduces that the preventive grinding and asymmetric grinding of curved rail head should be applied to Guang-Shen Line. Based on the period when the rail obligue crack initiates and annual volume of the Guang-Shen Line, it is proposed that the preventive grinding interval of the curved track is about 6 months. The asymmetric grinding of curved rail head can make the wheel-rail contact point move toward rail centre and apart from rail shoulder. Accordingly, the contact stress between the wheel and rail decreases and the rail obligue crack can be eliminated and lightened.更多还原