米轨内燃机车车轮踏面剥离现象研究

DF21型机车是专门为昆明铁路局米轨铁路制造的C0-C0轴式内燃机车，为了适应该线路的复杂曲线，采用了自导向径向转向架，目前共有12台机车投入运用。第1批2台机车于2003年4月投入运用，至2004年8月2台机车运用约15万km之后，都相继出现中间轮对踏面严重剥离的现象，通过采取相应整改措施，目前所有12台机车运用里程均已超过25万km，中间轮对踏面仍保持良好状态未再发生剥离，现对这一现象的机理和整改措施进行详细分析。     

踏面制动单元弹簧停车制动器作用原理简介

对我国及德国生产的踏面制动单元弹簧停车制动器的作用原理进行了介绍。     

踏面制动热-机耦合过程的数值仿真

列车踏面制动过程是一个复杂的大位移、动态接触热-机耦合问题，介绍了热-机耦合问题的求解方法，首次对某提速客车的双面踏面制动过程进行了数值仿真，并定量给出了车轮速度和温度的变化规律，为研究轮、瓦寿命提供了理论依据。     

A line-based skid mark segmentation system using image-processing methods

We developed a line-based skid mark segmentation and measurement system to solve issues related to randomness from pavement texture and measurement subjectivity at car accident scenes. The system was designed to operate along the longer straight lines that exist in boundaries between skid marks and pavement at the scene of an accident. The operational system consists of two processes: preprocessing and feature extraction. Preprocessing steps include skid mark positioning, slope angle detection, and segmentation, whereas feature extraction involves detecting light striations, striation segmentation, and calculating the widths of striations from images. Experimental validation and objective measurements illustrate that this system saves operation time and cost while performing with accuracy similar to that of manual methods.     

Measurement and analysis of tyre and tread block dynamics due to contact phenomena

This paper deals with the dynamic behaviour of tyres and it is aimed at describing their dynamic features in the frequency band above 1 kHz, a range difficult to manage due to measurement noise and to the unreliability of numerical models, where the main influence is that of tread and blocks. Measurements have been made possible by fixing three three-axial micro-electro-mechanical system accelerometers on the liner and exciting the tyre under test by means of a dedicated test bench, suitably designed and constructed. Different kinds of tests have been considered in this research and described in the present paper. All of them show that a strong link exists between contact phenomena and tyre response in the frequency band over 1 kHz. This field is dominated by the tread and block dynamic responses. Furthermore, it is shown that vibrations of a sliding tyre give contributions in that frequency range for the above-mentioned reasons. It is thought that the study of the tyre behaviour over 1 kHz, though affected by significant uncertainties, can provide a proper knowledge to improve breaking effectiveness.     

胎面单元对轮胎薄膜湿牵引性能的影响

在潮湿的天气或雨后，轮胎胎面或路面上存在一层很薄的水膜，该水膜使车辆行驶的牵引力降低。建立了轮胎胎面单元挤压膜问题的数学模型，并进行了数值求解，分析了胎面单元的几何参数，液膜厚度和柔性对轮胎薄膜湿牵引性能的影响，为轮胎胎面花纹的合理设计提供了理论依据。     

上海轨道交通8号线车辆车轮踏面设计优化及测试

针对上海轨道交通8号线车轮踏面异常磨耗情况,根据轮轨间的几何接触特性关系,采用了基于轮径差函数的方法,优化设计了新的车轮踏面外形;运用MATLAB/SUM LINK软件来搭建车辆模型,通过仿真模拟,比较了装有新、旧设计踏面的整车性能差异,得出新踏面外形具有明显减磨性能优势的结论。通过实际装车试验,分析了装有新、旧踏面车轮的磨耗情况,从而验证了新踏面外形具有明显减少钢轨和车轮之间的相互磨耗的特性的结论。     

车轮踏面多目标优化设计研究进展

车轮踏面优化设计是轨道交通系统的基本问题。根据车轮踏面优化模型的建立及其求解方法,车轮踏面优化设计的数值研究方法可以分为两类,即单目标优化设计方法和多目标优化设计方法。在综述轮轨踏面同步设计法、扩展方法、基于轮轨接触曲线的滚动半径差法和基于接触角曲线法等单目标优化方法的基础上,论证了车轮踏面优化是一个多目标优化问题,并给出了建立车轮踏面多目标优化模型的思路。车轮踏面多目标优化需要求解带约束的非凸不可微规划问题,求解精度和效率直接决定优化结果的可靠性和实用性。现有的求解方法包括遗传算法和拟高斯方法。针对现有计算方法存在计算量大、易早熟、收敛慢的缺点,提出求解车轮踏面多目标优化问题的响应面方法。该方法利用多项式响应面逼近目标函数和约束函数,避免了优化过程中由于数值求导带来的迭代振荡问题;同时该方法具有计算量小、收敛快的优点。以降低轮轨磨耗为目的对车轮踏面进行优化的实例表明,响应面方法能有效的优化车轮踏面。最后对车轮踏面这一课题的发展方向进行了展望。     

Measurement of stress distributions in truck tyre contact patch in real rolling conditions

Stress distributions on three orthogonal directions have been measured across the contact patch of truck tyres using the complex measuring system that contains a transducer assembly with 30 sensing elements placed in the road surface. The measurements have been performed in straight line, in real rolling conditions. Software applications for calibration, data acquisition, and data processing were developed. The influence of changes in inflation pressure and rolling speed on the shapes and sizes of truck tyre contact patch has been shown. The shapes and magnitudes of normal, longitudinal, and lateral stress distributions, measured at low speed, have been presented and commented. The effect of wheel toe-in and camber on the stress distribution results was observed. The paper highlights the impact of the longitudinal tread ribs on the shear stress distributions. The ratios of stress distributions in the truck tyre contact patch have been computed and discussed.