关键词： 轮轨滚动接触   轨枕空吊   焊接不平顺   有砟轨道   显式有限元法  

摘要： 采用显式有限元法建立考虑有砟道床非线性支撑的三维轮轨瞬态滚动接触模型,于时域内再现轨枕空吊和钢轨焊接接头不平顺共同激扰下的轮轨滚动接触行为,研究了轨枕的空吊间隙和数量对焊接不平顺区轮轨瞬态相互作用的影响。结果表明:轨枕完全空吊会进一步加剧焊接不平顺区的轮轨冲击效应,进而加大了钢轨表层材料的屈服变形,且屈服程度随空吊轨枕数量的增长而增长;焊接接头处2根毗邻轨枕完全空吊条件下,法向轮轨力、瞬态接触应力、接触斑面积和von Mises等效应变等轮轨接触参数较无轨枕空吊时分别增长14.5%、4.2%、8.5%和6.7%,轨面垂向位移的增幅达到72.0%,而接触斑内黏着与滑移区比例的变化则相对较小;当焊接接头处1根轨枕的空吊间隙超过1.0 mm或2根毗邻轨枕的空吊间隙超过1.3 mm时,前述轮轨接触参数会随着轨枕空吊间隙增长而增长迅速,直至出现轨枕完全空吊现象。

关键词： Wheel-track impact   conventional method   velocity-based method   acceleration-based method   unreliability   suspension damage   theoretical method   FE modelling  

摘要： Without considering either velocity or acceleration effects, the current conventional method presented in literature applies the vertical deflection of a wheel centre caused by a flat defect to the Hertzian contact theory. This method has been numerically and theoretically proved to be inappropriate and can incorrectly predict a higher wheel-rail impact force for a low speed than a high speed. Therefore, under a hypothesis of no wheel bouncing and sliding, two new methods, the velocity-based and the acceleration-based have been proposed. The former method takes the wheel centre deflection change in each computational increment from the Hertzian contact theory while the latter applies the wheel centre acceleration caused by the flat in revolutions to the wheel as a force in dynamic simulation, which interprets the speed effects on impacts precisely. A sensitivity study proves that the velocity-based method is unreliable as opposed to the acceleration-based method. A beam/rigid FE model has also been developed to inspect the wheel-track interaction by performing dynamic analysis in the time domain. It has been found out that the impact responses predicted by the FE analysis and the velocity method are similar and the FE results heavily depend on the compute increment, which implies the FE modelling in ABAQUS may be unreliable for this issue with current applied increments. Finally, the results calculated using the acceleration method have been employed to study the suspension/damper torsional stress caused by a wheel flat. This indicates that a wheel flat may lead to potential fatigue damage if without proper maintenance management.

关键词： 轨道超高   轮对-轨道接触   接触应力   轮轨   非线性  

摘要： 轨道超高是高速列车曲线行驶的主要参数之一,直接影响到车辆的安全性和轨道的耐久性。为研究轮轨垂向振动状态下曲线轨道超高的影响规律,基于动力学理论建立轮轨三维实体非线性接触的有限元模型,采用瞬态动力学分析方法,在曲线轨道高低不平顺激励下研究曲线轨道超高对轮对-曲线轨道非线性接触系统的动力影响。研究结果:低速在较大超高的轨道上行驶会增大车体横向振动,不同超高的舒适速度为190 km/h;车体垂向振动随着速度的增大受超高的影响逐渐减小;倾覆系数随着速度的增大呈非线性增大,内外侧轮轨脱轨系数差异在低速较大超高轨道中最大,且随着超高的增大差异逐渐减小;速度超过160 km/h时,轨距动态扩大量会迅速增大,超高会增加轨距动态扩大量,建议采取拉杆等措施予以加固;钢轨、轨枕及道床垂向振动随着车速增大而增大,超高影响较小,可忽略;超高引起内外侧轮轨接触应力完全不一致,法向接触应力以内侧轮轨较大,切向接触应力以外侧轮轨较大;速度超过160 km/h时,轮轨接触斑动态总滑动量会迅速增大,轨道超高会引起内侧轮轨接触斑动态滑动量大于外侧,其差值随着超高的增大而增大。

关键词： 轨道车辆   制动防滑控制   轮轨接触   黏着改善   黏着模型  

摘要： 针对轨道车辆制动工况下的低黏着特性,分析防滑控制作用下制动力调节引起轮轨间黏着变化和改善的原因;基于滑动功率和滑动能对Polach黏着模型进行改进,并考虑各轴随位置不同的黏着修正,给出适用于制动工况下的轮轨低黏着模型;基于Matlab/Simulink和AMESim的联合仿真,进行紧急制动工况下的制动防滑控制仿真分析,并与试验数据进行对比,验证所改进低黏着模型的有效性和实用性;提出基于速度差的统计指标,可对制动防滑控制过程的仿真有效性进行评估。结果表明,改进的黏着模型符合规范BS EN 15595—2018的黏着曲线仿真要求,方法简洁,计算高效,涉及参数较少,更好地再现了制动工况下轮轨间的低黏着状态,且能够直接应用到列车制动过程中的防滑控制实时仿真。

关键词： 柔性轮对   重载货车   车轮失圆   安全性  

摘要： 为研究重载货车振动特性,以我国轴重最大的某型30 t轴重重载货车为研究对象。首先采用有限元方法建立了轮对的弹性模型,进而在UM软件中进行总体集成,建立了考虑与不考虑轮对弹性的货车刚体模型以及刚柔耦合振动模型。然后选取径向偏差较大的某30 t重载货车车轮,采用与之对应的镟修后三个月、一年后和一年半后运营时间段的车轮多边形数据,从轮轨力的时域以及频域的角度分析车轮失圆对轮轨作用力的影响;并对两种模型曲线通过性做了研究。通过对结果分析可知,轮对的柔性结构能够一定程度上缓和了车辆与钢轨的刚性作用。随着车轮失圆加深,两种模型的差别向高阶发展,随着运行时间的增长,轮轨力表现更为强烈。说明车轮失圆极大程度的影响了轮对的柔性结构。

摘要： The world of today has the transportation sector growing and railway transportation system is contending all transportation modes by this time. This fact is because railway transportation system is able to carry a large number of passengers at low cost and reduced time while also being environmental friendly. Even if the railway is booming, there are things that are still challenging and need more attention, and among those challenge, there is the track irregularities. The irregularities have many causes and in this project the main cause of irregularities is the variation of track stiffness. Track irregularities including stiffness variation are known to accelerate the track deterioration and to affect the rail vehicle; but a little is known how this effect is correlated with train speeds, under dynamic loading conditions. This study aims to investigate the combined effect of rail vehicle speeds and track irregularities caused by railway spatial stiffness variation on the wheel and rail stresses, deformations and vertical displacements. Explicit dynamic finite element analysis using ABAQUS software package is used in this study. The model is composed of a train wheel rotating on a rail across several sleepers, which are fixed at their base. The equivalent average of the sleeper moduli is chosen to resemble the total average track modulus under the rail, in real situation. The variation of track stiffness in the model is achieved by changing the statistics of the randomly distributed sleeper moduli. It is found that increase in speeds and the longitudinal variation in track stiffness for a given track stiffness mean results in increased amplitude of oscillations of rail deflections, and reduction of a corresponding oscillation frequency, and in increased level of von Mises stresses at much higher level of stiffness variations. For the deflection of the rail as the speed changes the deflection varies as well. In this project considering the speed variation for exampl

关键词： 轮轨材料   重载列车   黏着系数   滑差   磨损  

摘要： 在自行研制的小型轮轨滚动磨损实验机上,以CL60车轮钢和U71Mn钢轨钢配副为研究对象,通过控制轮轨的转速,研究滑差对重载列车轮轨黏着特性与表层损伤的影响。结果表明:滑差对轮轨黏着特性存在显著影响,在所测试的若干工况下,随滑差增大,轮轨黏着系数增大;滑差影响轮轨的磨损量,随滑差增大,轮轨磨损量增加;轮轨表面硬度随滑差增大提高;不同滑差下轮轨表面磨损机制不同,纯滚动摩擦时轮轨以疲劳损伤为主;随滑差的增加,轮轨表面磨损机制由轻微的疲劳磨损转变为黏着磨损。此外,在相同滑差下,车轮表面损伤程度较钢轨严重。

关键词： 刚柔耦合   轮轨冲击   踏面损伤   车轮扁疤限值   多体动力学  

摘要： 为探究列车车轮旧扁疤对轮轨冲击的影响规律,建立了考虑柔性轮对的高速动车刚柔耦合模型和有限元扁疤损伤接触模型。分析了不同位置分布的单或双扁疤对轮轨冲击的影响,以避免车辆运行状态下发生跳轨冲击,保证运营安全,并为高速动车组安全运行时车轮损伤限值确定提供依据。分析结果表明:旧单扁疤产生的轮轨垂向冲击力随车速的增大先增大后减小,在100 km/h处达到峰值;速度为100~200 km/h时,当双扁疤间隔70°以下时,第一旧扁疤对第二旧扁疤有增益作用,当间隔70°以上时,增益明显减少,可视作独立扁疤;当车轮存在长度为30 mm的双扁疤时,车轮发生跳轨后最大冲击应力可以达到1059 MPa。

关键词： 有限元   弹性分析   塑性分析   偏斜分析  

摘要： 目的基于低速重载工程机械运行速度慢、载重量大等特点,对其进行定义,并提出关于其轮轨接触问题的解决办法。方法利用APDL语言建立轮轨接触分析参数化模型,通过非线性有限元接触分析技术对无轮缘车轮和轨道与有轮缘车轮和轨道进行对比分析;并通过Von-Mises应力云图对安装误差引起的偏斜运行轮轨结构进行分析。结果在轮轨结构横向截面与纵向截面的接触区域有塑性变形的产生,应力值降低且扩散面积增大;对无轮缘轮轨结构接触区和双轮缘轮轨结构接触区在相同的条件进行分析,无轮缘车轮-轨道的应力值明显更小;垂直偏斜对接触应力的变化影响较小,但长期接触会导致轨道或车轮单侧磨损;侧向力作用下会导致轮轨结构接触状态变差。结论在低速重载的工作条件下,轮轨结构材料接触应力值较小,易塑性变形;在相同的工作状态下,对无轮缘车轮-轨道结构与双轮缘车轮-轨道结构的接触区域进行对比,无轮缘车轮-轨道结构的最大接触应力值较小;低速重载工程机械的车轮垂直偏斜和运行过程的侧向力作用下的偏载,对整机运行稳定性产生较大影响。