浅谈不落轮旋车床的常见故障及处理方式

介绍了动车组检修关键设备不落轮旋车床在使用过程中出现的几种常见故障,分析了产生故障的原因,并提出一些常用故障的处理方法。     

Dynamic model and validation of an articulated steering wheel loader on slopes and over obstacles

This paper devotes both analytical and experimental efforts in developing a comprehensive dynamic model for an articulated steering wheel loader. The general motion of a wheel loader without suspension is described by seven degrees of freedom (DOF) (three for translation and four for rotation) in this model, which can be used to study the problem of wheel loader dynamics on slopes and over obstacles. A scale wheel loader was designed and manufactured to validate the dynamic model in three conditions (turning on level ground, turning on slopes, and passing over obstacles). The test results reasonably agree with the simulation results. The developed dynamic model was found to be useful and could serve as an important tool for analysing the stability of wheel loaders.     

120型控制阀造成行车抱闸的原因分析

结合近期铁路货车运用制动抱闸故障发生频繁情况深入分析,并提出改进建议。     

The role of the contact geometry in wheel–rail impact due to wheel flats

A thorough investigation of wheel–rail impact due to wheel flats is presented, together with a quantitative characterization of the main mechanisms and parameters. A criterion for the speed with respect to contact loss between wheel and rail is derived. In the subcritical speed regime, the magnitude of the impact force is shown to be directly related to the geometry of the flat, whereas in the transcritical speed regime a fictitious or effective flat depth exists, which decreases with the second order of the speed. In this domain, the position of impact shifts towards the end of the flat with increasing speed. The impact force increases with the second order of the speed in the subcritical speed regime and approximately the first order of the speed in the transcritical speed regime. The magnitude of the impact force is inversely proportional to the minimum circumferential curvature of the wheel tread defect in the subcritical speed regime, and to the effective minimum curvature in the transcritical case. The variation with the flat depth is less; the impact varies with the square root of the flat depth. The presented theory is in accordance with measurements reported in the literature and explains characteristic features in them.     

Minimum-time manoeuvring in electric vehicles with four wheel-individual-motors

The coordinated control of vehicle actuators is gaining more and more importance as new platforms are becoming available, with chassis endowed with many different actuators that may help controlling the vehicle motion. Furthermore, wheel individual motors allow using a single system to apply both positive and negative torques at the wheels, which can be actuated independently one from the other. In electric vehicles (EVs), moreover, such a freedom in the actuation mechanisms opens the way to the combined optimisation of performance and energy consumption issues. In this paper, the problem of minimum-time manoeuvring in EVs is addressed, and the proposed strategy is compared against a benchmark, a-causal optimal solution showing that only a negligible loss of performance is experienced.     

A method for testing railway wheel sets on a full-scale roller rig

Full-scale roller rigs for tests on a single axle enable the investigation of several dynamics and durability problems related with the design and operation of the railway rolling stock. In order to exploit the best potential of this test equipment, appropriate test procedures need to be defined, particularly in terms of actuators’ references, to make sure that meaningful wheel –rail contact conditions can be reproduced. The aim of this paper is to propose a new methodology to define the forces to be generated by the actuators in the rig in order to best reproduce the behaviour of a wheel set and especially the wheel –rail contact forces in a running condition of interest as obtained either from multi-body system (MBS) simulation or from on-track measurements. The method is supported by the use of a mathematical model of the roller rig and uses an iterative correction scheme, comparing the time histories of the contact force components from the roller rig test as predicted by the mathematical model to a set of target contact force time histories. Two methods are introduced, the first one considering a standard arrangement of the roller rig, the second one assuming that a differential gear is introduced in the rig, allowing different rolling speeds of the two rollers. Results are presented showing that the deviation of the roller rig test results from the considered targets can be kept within low tolerances (1% approximately) as far as the vertical and lateral contact forces on both wheels are concerned. For the longitudinal forces, larger deviations are obtained except in the case where a differential gear is introduced.     

防止和降低修船浮船坞作业污染水域的管理实践与思考

文中针对修船浮船坞作业存在的污染水域风险，在综合分析评判两起海损事故船浮船坞作业防污染措施得与失的基础上，分析原因、总结经验、寻找依据，提出了相应的管理对策措施和建议。     

An investigation on wheel/rail impact dynamics with a three-dimensional flat model

Wheel flat is one kind of railway train wheelset defects. It has great influence on wheel/rail dynamics and damages. In most of the presented studies, wheel/rail impact velocity or rolling radius variation of the wheel because of flat spot was taken into account to study the wheel/rail impact dynamics. In this paper, a three-dimensional wheel flat model considering the length, width and depth of the flat spot is established. Including the wheel rotation and wheel/rail contact geometry, a high-speed vehicle–rail coupling system dynamics model is developed to investigate the effect of the wheel flat on the wheel/rail dynamics. With time integration method of the models, the impact dynamics of the wheel/rail system with three types of flat width and five kinds of flat length are obtained. The results show that the width, the length of the wheel flat and the width/length ratio have a great influence on the wheel/rail impact dynamics. The wheel/rail impact dynamics of the flat with large width is more severe than with small width as the flat length is fixed. When a flat spot occurs, the permissible length of the wheel defect, needless to action, is 25?mm in maximum. The speed safety domain with three kinds of flat width/length ratio of a vehicle is obtained according to the wheel/rail vertical force limitation.     

国内外铁路车轴、车轮标准探讨

简要介绍了国外先进的车轴、车轮标准,并与我国现行标准进行了对比。     

地铁车辆轮重调整问题研究

通过建立地铁车辆轮重调整力学分析模型,推导出轮重变化的解析式。建立了A型地铁车辆轮重调整整车模型,通过分析计算找出整车轮重变化规律。利用理论推导及仿真计算结果能够很好地指导轮重调整试验,实现一次加垫调整就能满足轮重差要求的目标,节约试验工时,提高了工作效率。