On the overriding issue of train front end collision in rail vehicle dynamics

A three-dimensional dynamic model of crashed vehicles coupled with moving tracks is developed to research the dynamic behaviour of the train front end collision on tangent tracks. The three-dimensional dynamic model consists of a crashed vehicle model, moving track models, a simple wheel–rail contact model, a velocity-based coupler model and the model of energy absorption and anti-climbing devices. The vector method dealing with the nonlinear wheel–rail geometry is put forward in the paper. The developed model is applicable in the scope that central collisions occur on tangent tracks at low speeds. The examples of the vehicle impacting with a rigid wall and the train front end collision are carried out to obtain the dynamic responses of vehicles. The overriding issue is studied on the basis of the wheel rise in train collisions. The results show that the second bogie of the first colliding vehicle possesses the maximal wheel rise. The wheel rise increases with the increase of vehicles. However, the number of vehicles has tiny influence on the overriding in train collisions at low speeds. On the contrary, the impact speed has significant influence on the overriding in train collisions. The wheel rise increases rapidly if the impact speed is close to the critical speed of overriding. The large wheel rise is principally generated by the great coupler force related to the rigid impact in the axial direction.     

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.     

摩托车后轮液压盘式制动系统的开发（1）

液压盘式制动系统因技术先进、稳定性好、无自锁现象及维修方便等优点，在国外已被广泛应用于摩托车前、后轮制动器上，而我国则仅限于前轮制动器的使用，后轮制动器多使用技术相对简单的鼓式制动器。为提高我国摩托车的技术含量，摩托车后轮液压盘式制动器的研究非常必要，同时也是为摩托车制动系统向更高技术含量的防抱死制劝系统发展做好技术储备。     

个性化彩绘摩托车铝合金车轮的开发与改进

全自动彩绘印刷机的研发成功,避开了铝合金车轮表面处理为涂装的传统加工工艺,引进了设计和操作更简单的印刷工艺为铝合金车轮再开发的设计平台,使产品表面涂层均匀、色彩艳丽,在设计阶段可以更好地发挥设计人员的设计才能,在铝合金车轮的不同部位设计、印刷出各种不同类型的图案,甚至能使图案颜色不局限于2种,并可作出更加绚丽多姿的效果。     

Dynamics of railway wagons subjected to braking/traction torque

Braking or traction torque is regarded as an important source of wheelset skid and a potential source of derailment risk that adversely affects the safety levels of train operations; therefore, this research examines the effect of braking/traction torque to the longitudinal and lateral dynamics of wagons. This paper reports how train operations safety could be adversely affected due to various braking strategies. Sensitivity of wagon dynamics to braking severity is illustrated through numerical examples. The influence of wheel/rail interface friction coefficient and the effects of two types of track geometry defects on wheel unloading ratio and wagon pitch are also discussed in the paper.     

宋代23轮车轮战船复原研究

早在公元417年，中国就率先发明，建造并使用了明轮推进的船舶——轮船，比欧洲1543年在巴塞罗那第一次建造并进行实验的实船早1000多年。将单片桨划桨的间歇运动变为轮桨的连续运动，是机械技术上的一项重大发明，它大大地提高了船舶航速，直到19世纪50年代螺旋桨的发明和使用，才逐渐代替了明轮推进器。以明轮推进的船舶出现和使用长达1400多年。长期以来，人们只能依据少量历史文献，对中国古代轮船外貌作粗浅了解，究竟它的详细结构如何，一直未能进行深入、细致的研究。我们查阅了国内外有关轮船资料，分析古代陆用车结构与水车(翻车)结构之间内在联系与区别，依据中国传统的木构技术特点，古人极可能采用的形式，以结构合理，制造简单易行，安装更换方便为复原指导思想，注意了船舶的特殊条件限制和人机功能学及实战特殊要求，对宋代23轮车轮古战船轮桨，舱内等结构进行了复原研究。同时对船舶外观造型，幡帜、彩绘、兵器等进行了复原探讨。     

根据车轮抬升量评判车辆脱轨的方法与准则

分析比较了目前国际上常用的车辆脱轨评价标准的特点及其不足，指出我国现行国家标准GB5599-85评判车辆脱轨所存在的突出问题，在此基础上提出直接根据车轮抬升量评判脱轨的原理与方法，运用车辆-轨道耦合动力学理论，对单轮对爬轨脱轨和跳轨脱轨过程进行了计算仿真，得出脱轨系数超限时间与车轮抬升量之间的关系，提出最大允许超限时间为35ms的安全准则，并进行了实际线路工况下整车轮轨相互作用脱轨仿真验证，最后提出针对我国车辆脱轨评判的建议标准及其实施细则。     

新型轮挡研究

安全是一个永恒的主题,它是赖以生存和发展的基础。地面安全是行业监管的工作重点。在地面停放过程中,由于天气、环境、突发意外事件、人为失误等因素可能会造成的地面事故。轮挡指在存放库或其他临时场地时用于限制轮胎位置的装置,轮挡是常用的地面安全设备。     

宝骏630电控发动机转速间歇性异常升高故障

通过根据ECM的传感器及信号输入及输出的逻辑关系,对一辆宝骏630手动档发动机换档过程转速异常升高的故障进行诊断和查找,最终找出导致故障的原因。     

Investigation of the impact of locomotive creep control on wear under changing contact conditions

This paper presents the locomotive traction controller performance with respect to the track wear under different operation conditions. In particular, an investigation into the dynamic response of a locomotive under changing wheel–rail friction conditions is performed with an aim to determine the effect of controller setting on track wear. Simulation using a full-scale longitudinal–vertical locomotive dynamic model shows that the appropriately designed creep threshold, controller, settings can effectively maintain a high tractive effort while avoiding excessive rail damage due to wear, especially during acceleration under low speed.