Design of an optimised wheel profile for rail vehicles operating on two-track gauges

This article sets out an optimum synthesis methodology for wheel profiles of railway vehicles in order to secure good dynamic behaviour with different track configurations. Specifically, the optimisation process has been applied to the case of rail wheelsets mounted on double-gauge bogies that move over two different gauges, which also have different types of rail: the Iberian gauge (1668 mm) and the International Union of Railways (UIC) gauge (1435 mm). Optimisation is performed using Genetic Algorithms and traditional optimisation methods in a complementary way. The objective function used is based on an ideal equivalent conicity curve which ensures good stability on straight sections and also proper negotiation of curves. To this end, the curve is constructed in such a way that it is constant with a low value for small lateral wheelset displacements (with regard to stability), and increases as the displacements increase (to facilitate negotiation of curved sections). Using this kind of ideal conicity curve also enables a wheel profile to be secured where the contact points have a larger distribution over the active contact areas, making wear more homogeneous and reducing stresses. The result is a wheel profile with a conicity that is closer to the target conicity for both gauges studied, producing better curve negotiation while maintaining good stability on straight sections of track. The article shows the resultant wheel profile, the contact curves it produces, and a number of dynamic analyses demonstrating better dynamic behaviour of the synthesised wheel on curved sections with respect to the original wheel.     

超精磨削油石的磨削性能试验研究

无心超精磨削技术是提高滚动轴承的圆柱滚子零件表面质量的主要技术之一，根据生产的要求，对影响油石的磨削性能的因素进行试验，为超精磨削加工提供参考数据选择的依据。     

浅海波导中水平时反线列阵布放深度选择研究

  目的  为提高实际海洋环境中不同季节时的水声通信和声呐探测能力,对浅海声传播的最佳深度现象进行研究。  方法  运用简正波方法,针对不同季节的典型声速剖面,计算典型声速剖面下不同频率和不同接收点深度的非相干声传播损失随距离和深度变化的伪彩图,研究不同声速剖面对声传播最佳深度的影响。  结果  结果显示：低频时,最佳深度不随声速剖面和声源深度的变化而变化,始终位于海水层中层附近;高频时,当声源位于等梯度海水层或负跃层下较深海水的等温层时,最佳深度位于声源深度和声源在等声速层内的对称深度,正梯度和负梯度下的最佳深度位于声源深度处。  结论  研究结果可为水声通信的接收点深度和被动声呐位置的选取提供参考。     

打磨处理改善焊缝疲劳性能的试验研究

由于高强度钢的使用，船舶结构许用应力水平的提高，船舶结构的疲劳强度越来越受到关注。船舶结构的疲劳寿命取决于其焊接结构的疲劳寿命。因此，了解焊缝几何参数对焊件疲劳强度的影响以及采用经济实用的方法改善船舶结构的疲劳性能是十分重要的。本文首先对焊缝几何参数对焊件疲劳寿命的影响进行了分析，在此基础上用ABS钢和945钢两种钢板做试件，分别进行了简单拉伸实验及打磨和未打磨条件下对接接头的疲劳试验。试验结果表明焊件的疲劳寿命可以通过打磨焊缝得到改善；尤其对于高强度钢焊件。试验还说明手工打磨焊缝和机械磨削焊缝对焊件疲劳强度的改善效果差别很大，疲劳寿命的分散性也很大。因此，应当对改善焊件疲劳寿命的工艺进行更详细的研究。     

基于AVL EXCITE TD的凸轮型线仿真优化

在现代发动机开发过程中,CAE软件的应用已经成为降低开发成本和缩短开发周期的主要手段.针对某微小型汽车发动机性能提升的改进工作,利用AVL Excite Timing Drive软件对发动机凸轮轴型线进行优化设计.建立了该发动机的单阀系统模型,在给定的配气机构零件基础上利用多段函数的数学方式优化了凸轮轴的缓冲段和工作段型线.优化后的结果表明,采用梯形函数形式的缓冲段,以及分段函数形式的工作段的凸轮轴型线,既能满足配气机构的动力学和运动学要求,同时达到了提高发动机中低速扭矩的性能目标,有效降低了整机的开发成本和周期.     

河道回水曲线计算研究

文章以天然河道的流段划分为切入点,介绍了河道回水曲线的计算原理及方法,并结合珠江流域某天然河道回水曲线计算实例,对比分析了传统手工算法和Excel电子表格算法的优缺点。实践证明,Excel电子表格算法的计算精度较高,且能避免大量的计算和绘图工作量,具有明显的优势。     

Carbody elastic vibrations of high-speed vehicles caused by bogie hunting instability

In particular locations of the high-speed track, the worn wheel profile matched up with the worn rail profile will lead to an extremely high-conicity wheel–rail contact. Consequently, the bogie hunting instability arises, which further results in the so-called carbody shaking phenomenon. In this paper, the carbody elastic vibrations of a high-speed vehicle in service are firstly introduced. Modal tests are conducted to identity the elastic modes of the carbody. The ride comfort and running safety indices for the tested vehicle are evaluated. The rigid–flexible coupling dynamic model for the high-speed passenger car is then developed by using the FE and MBS coupling approach. The rail profiles in those particular locations are measured and further integrated into the simulation model to reproduce the bogie hunting and carbody elastic vibrations. The effects of wheel and rail wear on the vehicle system response, e.g. wheelset bifurcation graph and carbody vibrations, are studied. Two improvement measures, including the wheel profile modification and rail grinding, are proposed to provide possible solutions. It is found that the wheel–rail contact conicity can be lowered by decreasing wheel flange thickness or grinding rail corner, which is expected to improve the bogie hunting stability under worn rail and worn wheel conditions. The carbody elastic vibrations caused by bogie hunting instability can be further restrained.     

基于轮轨垂向力的波磨状态估算方法

为了探明轮轨垂向力与波磨状态之间的映射关系并采用轮轨力检测数据定量评价波磨严重程度,以中国CRTSⅡ高铁线路与服役动车组典型参数构建三维轮轨动力学有限元模型;细化波磨区段钢轨表面不平顺特征,采用高速综合检测列车在高铁波磨区段上实测轮轨垂向力时频数据验证有限元模型输出结果的准确性;模拟了车辆运行速度为300 km·h^-1时波长在40~180 mm波磨激励下的轮轨垂向力,分析了其时频域分布特性;引入轨面不平顺变化率表征波磨沿钢轨纵向的变化特性,采用非线性最小二乘法与有理式方程拟合了不同波长条件下轮轨垂向力大值与轨面不平顺变化率之间的函数关系,分析了钢轨Pinned-Pinned固有共振频率及其半值振动模态对拟合参数曲线的影响,并推导了基于轮轨垂向力的波磨谷深估算方法;该谷深估算方法在某高铁线路波磨状态监测中初步试用,共发现32个波磨区段,并对比了波磨区段上实测谷深和估算谷深。分析结果表明：谷深估算值与实测值相关系数为0.97,两者具有较高的线性相关性;在谷深估算值大于0.08 mm时,估算值与实测值之间的均方根差约为0.01mm,基于谷深估算方法作出波磨打磨整治决策时的误判率约为6.25%,说明谷深估算方法在实际高铁线路上具有较好的适用性。     

与环境相协调的公路线形灵活性设计方法研究

分析国内外公路线形与环境相协调灵活性设计的发展现状与存在的主要问题,提出基于运动视觉的公路线形灵活性设计的设计原则及应用中应注意的问题。     

朔黄重载铁路线路设备合理修理周期研究北大核心

基于朔黄铁路线路设备维修现状,通过理论分析、室内试验和现场测试探讨适用于该铁路线路设备的修理周期。结果表明:直线区段钢轨大修周期为1 390~1 650 Mt通过总质量;半径400~1 500 m曲线区段钢轨换轨周期为300~800 Mt通过总质量;建议在通过总质量达到60 Mt前进行预防性钢轨打磨,通过总质量超过150 Mt时进行修理性钢轨打磨;直线区段扣件更换周期与钢轨大修周期相同;道床每年捣固2~3遍,25、30 t轴重条件下通过总质量分别达到1 300~1 500 Mt、1 200~1 300 Mt时进行道床清筛。