高速受流性能探讨

简述高速情况下影响机车受流性能的几个主要因素及其机理， 并对提高受流性能提出了简统化的设想。     

橡胶轮转向架对车辆曲线通过性能的影响

重点分析了橡胶轮转向架车辆的特色技术对车辆曲线通过性能的影响,分析对象包括承重与导向橡胶轮胎、单向止推轴承和空气弹簧,分析内容侧重于承重与导向橡胶轮胎和空气弹簧漏气以及单向止推轴承处于非正常工作状态对曲线通过安全性和轮胎磨耗的影响。     

Rail vehicle wheel wear prediction: a comparison between analytical and experimental approaches

There are a number of theoretical and practical techniques to compute rail vehicle wheel wear. For instance, the Archard equation is a well-known tool to determine the worn volume in sliding contact, as a function of normal load, sliding distance and the surface hardness. Of course, the wear coefficient (called K) used in this equation to differentiate the wear models implicitly comprises the conditions that govern the contact surface. Two situations can be taken into account when considering a sliding contact in a rail vehicle wheels, particularly along a curved track: (i) when the radial force prevails the lateral tangential force, which is mainly the frictional force but before flanging and (ii) during flange contact. Also, the Archard equation is employed within the tread and flange regions separately, both the regions being of interest in this paper. A number of approaches are then used to find the distance slid. The authors compare the field test results and the outcome of the analytical approaches. When the wheel wear results acquired from the two test bogies on Iranian Railways, all technical (rigid frame bogies with new assemblies and components) and operational items were identical, except for changing the bogie orientation in the second test trial for a short period. Good agreement was found between the analytical and practical investigations.     

Tangential force variation due to the bogie direction reversal procedure

A range of tangential forces is generated within the contact patch when a wheelset moves on the rail. These forces are intensified when incorporating curved tracks and motored axle rail vehicles [Arrus, P., de Pater, A.D. and Meyers, P., 2002, The stationary motion of a one-axle vehicle along a circular curve with real rail and wheel profiles. Vehicle System Dynamics, 37(1), 29-58]. The wheelset is subject to flange contact if an unbalanced force remains in a curve towards the high rail gauge face. The resultant force in the transverse direction includes the lateral force, the radial force, and the creep forces in addition to the effect of the frequent wheelset displacement due to the kinematic oscillation [Iwnicki, S., 2003, Simulation of wheel-rail contact forces. Fatigue Fracture Engineering Material Structure, 26, 887-900]. This article has focused on a potential variation in some of the forces cited when the wheelset is subject to backward and forward movements. A severe wear rate observed within the wheel flange region in Iranian Railways was investigated by operating a test bogie on a curvaceous track. An obvious improvement in the wear rate and wear pattern of the wheels was attained when the second test bogie encountered a bogie direction reversal procedure. This enhancement is considered in this article from the force analysis standpoint.     

氩弧表面熔敷耐磨覆层工艺研究

研究用氩弧加热在低碳钢表面熔敷耐磨覆层的工艺,该工艺能方便快速方便地对低碳钢表面进行强化,表面覆层成分和性能调整容易,由该工艺获得的复合材料具有基体的强韧性和表层的耐磨性,覆层与基体的结合为冶金结合,获得的耐磨覆层硬度达47.3HRC,耐泥沙磨损性能达低碳钢的5.8倍。     

铝基复合材料对铜基粉末冶金材料的摩擦磨损特性

通过铝基复合材料对铜基粉末冶金材料之间的摩擦试验,讨论了两种材料之间的摩擦磨损特性,说明 两种材料的摩擦因数和摩擦稳定性符合高速列车对制动材料的要求。最后分析了铝基复合材料表面的磨损情 况,说明了它的磨损是剥落、粘着和磨粒磨损共同作用的结果。     

Modelling of wear and fatigue defect formation in wheel–rail contact

The model for analysing wear and fatigue defect formation is developed based on the approaches of contact and fracture mechanics. The model includes the solution of the contact problem for the wheel and rail to find the shape, size and position of the contact zones and the contact stresses and calculation of the surface wear and the function of damage accumulation in the rail and wheel. The wear rate and the worn-profile evolution of the wheel surface are calculated using both statistic and deterministic approaches to modelling of vehicle dynamics (tribo-dynamic modelling). The influence of the evolution of the wheel–rail profiles due to wear on the damage accumulation process is analysed. It is shown that for some values of the wear rate coefficient, the wear process can prevent the crack initiation under the wheel surface.     

Wear rate estimation of train wheels using dynamic simulations and field measurements

Wheel–rail wear is one of the important problems in the railway industry, especially from the point of safety, maintenance, and replacement cost. To investigate this phenomenon, it is necessary to simulate the wheel–rail interaction. The simulation results and in particular the wear number is not tangible enough to explain the wear condition of the system. For one set of simulation performed on two different railway systems one could obtain the same wear numbers, of say 100, while having two completely different wear rates. In order to have a better understanding of the wear condition, it is proposed to convert the wear numbers to wear rates. In doing so by measuring the wear rate, one determines the rate at which the wheel flange thickness is reduced. In this research, a new approach has been proposed to determine the wheel wear rate through multi-body dynamic analysis and simulation and the field measurements carried out on the fleet of one of Tehran's subway lines. This procedure could also be expanded to determine a wear criterion for specific lines and their fleets. Having this wear criterion would provide a better understanding of the simulation results either prior to the construction of railway lines or for the presently used ones. In other words, designers can simulate a railway line, not being constructed yet, and with a good approximation determine the critical points along the line with high wear rates, and make necessary modifications to decrease the wear.     

铜氧化对粉末冶金材料摩擦性能的影响

将增强基体组无铜粉氧化与未氧化的两种铁基粉末冶金材料在ＭＭ－１０００型摩擦材料试验机上进行对比制动试验，测定了摩擦系数与转速、压力的关系曲线及磨损量。结果表明，若加的铅粉发生氧化而真空烧结时不能被还原，则ＣｕＯ可成为磨粒磨损的磨料，使摩擦材料及对偶的耐磨性降低。     

既有线新型提速客车转向架方案选型的研究

文章从既有线旅客列车提速必须解决列车的曲线通过性能和直线高速运行性能的矛盾出发,简要介绍了国内外径向转向架的发展状况。通过分析径向转向架的原理及其基本模式,结合2种自导向径向转向架方案,采用虚拟样机技术对其进行了动力学仿真分析。结果表明:2种转向架方案均能在具有良好的高速直线动力学性能的同时,提高曲线通过性能,降低轮轨磨耗。