The effect of wheel set gyroscopic action on the hunting stability of high-speed trains

This study explores the effects of wheel set gyroscopic action on hunting stability by calculating linear and nonlinear critical speeds. First, a dynamic model for a high-speed vehicle with 23 degrees of freedom is developed by considering wheel set gyroscopic action. The linear and nonlinear critical speeds are calculated by eigenvalue analysis and drawing a bifurcation map, respectively. Two computer programs for linear and nonlinear stability analysis are developed. Second, based on an actual high-speed vehicle in China, the effects of wheel set gyroscopic action on hunting stability are quantitatively investigated using computer simulation. Furthermore, the difference between the effects of gyroscopic moments about the x-axis and z-axis is discussed. The results show that the moment about the x-axis is harmful to hunting stability, but the moment about the z-axis is beneficial to hunting stability. However, the integrated effect of these two moments can enhance the critical speeds and suppress the hunting motion.     

Further study on the wheel–rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

A comprehensive dynamic finite-element simulation method was proposed to study the wheel–rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel–rail materials and thermal stress due to the wheel–rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel–rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel–rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.     

A locomotive–track coupled vertical dynamics model with gear transmissions

A gear transmission system is a key element in a locomotive for the transmission of traction or braking forces between the motor and the wheel–rail interface. Its dynamic performance has a direct effect on the operational reliability of the locomotive and its components. This paper proposes a comprehensive locomotive–track coupled vertical dynamics model, in which the locomotive is driven by axle-hung motors. In this coupled dynamics model, the dynamic interactions between the gear transmission system and the other components, e.g. motor and wheelset, are considered based on the detailed analysis of its structural properties and working mechanism. Thus, the mechanical transmission system for power delivery from the motor to the wheelset via gear transmission is coupled with a traditional locomotive–track dynamics system via the wheel–rail contact interface and the gear mesh interface. This developed dynamics model enables investigations of the dynamic performance of the entire dynamics system under the excitations from the wheel–rail contact interface and/or the gear mesh interface. Dynamic interactions are demonstrated by numerical simulations using this dynamics model. The results indicate that both of the excitations from the wheel–rail contact interface and the gear mesh interface have a significant effect on the dynamic responses of the components in this coupled dynamics system.     

转换轨及轮径校准对全自动驾驶地铁出入线平纵断面设计要求

综合考虑转换轨及轮径校准的概念与功能,结合全自动驾驶的作业模式,对全自动驾驶地铁出入线转换轨和轮径校准设置必要性、位置及其对线路平纵断面设计要求进行分析,提出:①对于场段与正线控制权不一致的,需设置转换轨进行控制权交接;②对于场段与正线控制权一致的,理论上无需设置转换轨进行驾驶模式转换,但鉴于备用模式下仍需采用GOA3以下级别的驾驶模式,建议现阶段仍需设置转换轨;③转换轨宜设置在车辆基地一端;④轮径校准段需保证35m的平直坡段;⑤转换轨(轮径校准段以外部分)坡度不宜大于24‰,若坡度大于24‰,则需验算一度停车再启动能力,且坡度不得大于35‰。     

地铁车辆噪声现状及分析

随着城市轨道交通车辆的快速发展,乘客对地铁车辆的舒适性提出了更高的要求,地铁车辆运营阶段的噪声问题成为目前广泛关注的热点问题,也是亟待解决的问题。文章从地铁车辆的噪声现状入手,分析轮轨相互作用引起的轮轨噪声问题,车体和薄弱环节的隔声与密封问题,以及隧道运行环境会产生混响声场环境差异问题等,为车辆噪声控制提供依据并指明方向。     

基于前景理论和直觉模糊集的编组站布局调整决策研究

为提升编组站布局调整方案的决策水平,考虑未来不同的运输需求增长状态对决策者行为心理的影响,提出基于前景理论与直觉模糊集的编组站布局调整决策模型。首先,构建编组站布局调整方案比选指标体系,涵盖空间分布的合理性、适应性、协调性、对社会的影响、经济性5个指标层;其次,利用直觉模糊集表征决策者对方案属性的主观评价值及犹豫度,并构造得分函数得到方案属性的综合得分值;然后,引入前景理论考虑决策者在不同运输需求增长状态下的不确定型偏好,结合灰靶决策理论构造三参照点计算编组站布局调整方案的综合前景价值;最后采用VIKOR决策方法对方案进行优选。通过某枢纽编组站布局调整实例,研究结果表明,A2为最优调整方案,与实际确定方案相吻合,验证了决策模型的有效性和实用性。     

城轨车辆轮重减载试验探讨

轮重减载率是评定城轨车辆运行安全性的重要指标之一,文章介绍了城轨车辆轮重减载的两种试验方法,并对其进行了对比。     

基于ADAMS的弹性车轮振动分析

通过ADAMS VIEW软件建立模型,采用将弹性车轮引入轮毂电机系统的使用,通过编写接触算法解决动态接触时的高频振动问题,并通过参数优化选择,来达到如何能最大程度并且合理的降低轮芯处轮毂电机系统所受到的振动冲击目的。研究结果表明,弹性车轮的引入能够很大程度上减少通过轨缝时对轮毂电机产生的冲击,在对刚度参数进行合理的选择分析后,最高减小了78.5%的正向冲击加速度以及56.1%的负向冲击加速度。能够有效的达到减小轮毂电机冲击,降低了电机在机械方面安全性隐患的目的。     

450MHz无线列调电台接收门限的温度补偿

450MHz无线列调电台会因外界环境温度变化RSSI输出电平发生温度漂移,造成接收门限的温度漂移。为此研究用软件方法解决该问题。     

重载货车车轮踏面优化研究

对近期开发的基于法向间隙的车轮踏面优化方法进行改进,根据三维非赫兹滚动接触理论对轮轨间隙求解范围进行计算,使所求解的轮轨间隙具有实际的物理意义.针对我国重载货车车轮圆周磨耗严重的问题,对现有重载货车车轮踏面进行优化.利用车辆-轨道耦合动力学理论及三维弹性体非赫兹滚动接触理论对优化前后车轮踏面的静态接触性能及动态接触性能进行分析.结果表明:优化后轮轨界面之间可达到较好的匹配,且合理选择踏面不同区域的权数可同时保证车辆直线运行与曲线通过时的轮轨接触应力较小,从而达到有效降低轮轨磨耗的目的.