Application of Moiré interferometry to reconstruction of residual stress in cut railroad car wheels

Railroad car wheels develop residual stresses both in their manufacture and while in service. Knowledge of the residual stress distribution and its variation over time is necessary for the prediction of wheel service life and possible catastrophic failure. It is also vital for the safety of railway transportation. Although a theoretical solution is possible, it remains complex. Alternatively, the solution may be also obtained by using experimental measurements assisted by the theory of mechanics. An approach known as “physically-based enhancement of experimental data” formulated and subsequently developed and tested is the best available experimental-numerical tool for the reconstruction of acquired residual hoop stress component in railroad car wheels. This paper presents the formulation, approach and results of the analysis performed on experimental data obtained from investigations of the passenger and freight wheels during a saw cutting process. A discussion on the precision of the results has been included.     

Analysis of internal cracks in railway wheels under experimentally determined pressure distributions

In recent years much effort has been devoted to the definition of design approaches of railway systems based on the analysis of the system itself and on accurate knowledge of its effective working conditions. In this paper, the attention is focused on railway wheels. This latter component is subjected to different types of damage: sub-surface crack propagation is considered. The prediction of the evolution of this process depends on the knowledge of the stress intensity factors concerning modes I, II and III, which are dependant both on the total load acting on the wheel and on how the load is transmitted through the wheel/rail interface. However, until now the solutions commonly used consider a theoretical (Hertzian) pressure distribution, even if, due to wear or to the dynamic phenomena, the actual contact patch can be strongly different for most of the lifespan of the wheel. An approach is developed with the aim to solve the case of an internally cracked wheel subjected to an arbitrary contact patch and pressure distribution. It is based on Boussinesq's formulae and utilises a three-dimensional finite element model of the part of the wheel close to the crack to calculate the stress intensity factors along a curvilinear crack front. Pressure distributions experimentally determined by means of a technique based on the reflection of high-frequency ultrasonic waves from the wheel–rail interface were applied to internal cracks in wheels: the results were critically compared with the those obtained by considering Hertzian pressure distributions, the aim being the assessment of the influence of the contact conditions in respect of damage cause by internal crack propagation.     

Measurement of the residual stresses in the treads of railway wheels by the acoustoelasticity method

In this work, we present data on the residual stresses measured in the treads of 957-mmdiameter railway wheels using a nondestructive ultrasonic method on an ИH-5101A device. The measurement results show that the residual stresses are compressive and modulo increasing from the center to the periphery for each tested point. The reliability of the data is confirmed by a destructive method (cutting a wheel along its axis).     

Simulation of the development of a railway wheel profile through wear

In this paper a method of calculation is presented for determination of the evolution by wear of railway wheels. The results are compared with the development of the profile of the wheels in the Amsterdam Metro, and satisfactory agreement is achieved. For ordinary railway lines the agreement is worse, since we did not take into account wear due to flanging.     

在役火车轮状态自动检测方法初探

简介了国内外火车轮检测的现有技术,在基于涡流检测技术和机、电、液一体化控制技术之上,提出一种自动检测在役火车轮状态的方法,并且通过模拟试验证明该方法有效。     

Surface cracks initiation on carbon steel railway wheels under concurrent load of continuous rolling contact and cyclic frictional heat

Focusing on the durability of carbon steel railway wheels, so-called tread thermal cracks, one of severe damages on the tread surface, were investigated to understand the cracks generation processes involving initiation and propagation. We have demonstrated that tread thermal cracks can be experimentally reproduced under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, through the experiments using an actual railway wheel. Relations of residual stress, cracks configuration and fracture surface were examined to consider the crack generation process. Plastic deformation and thermal stress near the surface result in substantial tensile residual stress, which causes the generation of cracks.     

Three-dimensional finite element analysis of multi-stage hot forming of railway wheels

Three-dimensional finite element analyses has been carried out using DEFORM 3D software on multi-stage hot forming of railway wheels involving the processes of upsetting, forging, and punching of wheels. Thermal analysis related to heating the blank in furnace and all intermediate heat transfer stages between deforming operations have been conducted. Rigid viscoplastic finite element method has been utilized for coupled thermo-mechanical analysis of the processes. Modeling of punching the wheel bore has been carried out using Cockcroft and Latham fracture criterion. Evolution of thermo-mechanical parameters at selected points within the workpiece has been studied in detail. The method of simulating the effects of various process parameters has been explained using relevant mathematical relations. This study shows that design, optimization, and analysis of process perturbations for multi-stage railway wheel manufacturing process can be done efficiently in three-dimensional finite element simulations instead of conventional time and cost intensive trials. It might be necessary to use the results of finite element analysis in shop-floor to enhance productivity and reduce wheel rejection.     

Temperature fields in grinding by abrasive wheels

A method is proposed for calculating the temperatures at the surface of the workpiece and within its interior on grinding by abrasive wheels of different design (discontinuous, composite, or hybrid wheels). On that basis, the temperature fields in the cutting zone are calculated.

     

基于Hilbert-Huang变换的列车车轮失圆故障诊断

研究列车车轮失圆的检测与诊断问题,采用基于改进的希尔伯特-黄变换(Hilbert-Huang transform,简称HHT)的处理方法,首先,针对HHT方法固有的模态混叠现象,提出一种形态滤波-能量原则算法;然后,建立车辆轨道耦合动力学模型和典型的车轮故障模型,计算轴箱垂向振动的动态响应;最后,运用改进的HHT分析方法提取正常车轮、多边形化车轮和擦伤车轮引起的轴箱垂向振动的特征。研究结果表明,正常车轮与故障车轮之间以及不同类型故障的车轮之间Hilbert谱差异显著,可见该方法能够有效诊断车轮失圆故障。     

Train wheel diagnostics by laser ultrasonics

The integrity of the wheel is very important for the safety of railway. In this paper a laser-ultrasonic diagnostic measurement procedure has been designed for the inspection of the train wheels with the aid of a FE-model simulating the ultrasound propagation within the wheel itself.The laser-ultrasonic method exploits an air-coupled ultrasonic probe that detects the ultrasonic waves generated by a high-energy pulsed laser. As a result, the measurement chain is completely non-contact, from generation to detection, this making it possible to considerably speed up the testing set-up time and make it more flexible. This is an important advantage with respect to the conventional NDT technologies currently applied to train component diagnostics, as contact phase array methods. Laser ultrasonics is a complete remote technique since both the laser source and the receiving probe are installed in the proximity of the wheel directly on the bogie and therefore it is a more flexible technology with respect to standard techniques applied for wheel train diagnostics, as phased array.The applications of laser-ultrasonic technique available in the state-of-the-art work with high energy ultrasonic waves to guarantee good signal to noise ratio. Therefore, conventional laser-ultrasonic systems operates under ablative regime that assures high energy ultrasonic waves generation. On the other hand, the ablation produces damages on the surface of the component inspected. In this paper, it has been demonstrated that it is possible to work with lower energy waves, i.e. in the limit between ablative and thermo-elastic regime, if the experiment is properly designed on the basis of a numerical model. This operation regime allowed to guarantee a material removal below the threshold admitted in rail wheel application. The diagnostic procedure developed has been applied for the inspection of train wheels provided by the Italian railway company Trenitalia, on which dominant wheel failure cracks have been expressly created.     

Improvement of Adhesion of the Wheels of the Railway Carriage to the Rails by Means of Supply of the Scale and Magnetite Particles to the Contact Zone

The article proposes a method to improve adhesion of the wheels to the rails of the railway carriage by means of supply of abrasive loose materials as an alternative to quartz sand to the zone of their contact: metal scale (Fe₃O₄) being the waste of rolling and forging, as well as the iron oxide—magnetite (FeO · Fe₂O₃) of the natural origin. The comparative assessment of efficiency of use of scale and magnetite was carried out in relation to quartz sand traditionally used for railway transport. The adhesion coefficient and wear intensity are used as comparison criteria.     

车轮多边形磨耗统计规律及关键影响因素分析

针对列车车轮多边形磨耗问题广泛存在于轨道交通运输领域,会导致车辆/轨道系统产生高频的振动冲击,严重影响车辆和轨道系统零部件的使用寿命,危及行车安全这一问题,调查了大量车轮的多边形磨耗情况并进行统计分析,掌握了高速列车车轮多边形磨耗问题的现状和特点。以18～20阶多边形磨耗车辆为例,通过理论研究和试验分析(试验分析包括车辆系统振动特性测试和转向架模态特性测试),对车轮多边形磨耗的根本原因及诱导因素进行研究。研究发现,轮轨系统在580 Hz频率附近存在固有模态是导致车辆发生18～20阶多边形磨耗的根本原因,轮轨表面的各种不平顺能激发或者加剧轮轨系统在580 Hz频率附近的模态共振,从而诱发车轮多边形磨耗的产生。该结果可为高速列车车轮多边形磨耗问题的防止和进一步研究提供参考。     

A study on life evaluation & prediction of railway vehicle contactor based on accelerated life test data

In this recent tendency, an accelerated life test (ALT) is used to evaluate stability and reliability of machinery parts and systems for short periods. As ALT is performed by applying high stress compared to normal use conditions in a short time, we can rapidly evaluate the life of the machinery and obtain reliability values. In this paper, we conduct the accelerated life test for a railway vehicle contactor, constructing the real-time monitoring system. Based on ALT data, we can determine the contactor's failure mode and mechanism, and estimate reliability values. Consequently, we will examine the method of evaluating the life of railway vehicle contactors through an estimation of the interesting value - relationship between life and stress, mean time to failure (MTTF), percentile B100P life etc. in normal use conditions.     

冲角对低地板车辆轮轨接触状况的影响

针对城市轨道交通中低地板车辆车轮经常出现的轮缘严重磨耗现象,研究其轮轨接触状况,由于城市轨道交通中小半径曲线较多,存在较大的冲角,为研究冲角对轮轨接触状况的影响,利用轮轨型面测量仪测量运用中的70%低地板车辆车轮与钢轨型面,建立具有不同冲角的车轮与钢轨接触模型,在横向力与牵引力矩作用下应用非线性有限元法进行弹塑性接触计算,分析不同工况下的等效应力及接触斑的变化规律,研究冲角、横向力与牵引力矩对钢轨接触状况的影响。通过计算分析得出以下结论：具有不同冲角的轮轨接触斑形状几乎相同,踏面接触斑近似矩形,轮缘接触斑相对狭长,容易造成轮缘磨耗;冲角增大,轮缘接触斑相对踏面接触斑的超前值增大;随着冲角的增大,轮轨最大等效应力逐渐增大,磨耗功率增大,故在轮轨型面匹配和车辆结构设计中应尽量将轮轨冲角控制在1°以内。     

Assessment of Al2O3 and superabrasive wheels in nickel-based alloy grinding

This paper presents experimental research on nickel-based alloy grinding using superabrasive wheels and Al₂O₃ wheels. Through on-line monitoring and off-line inspection, grinding performance and cost are studied based on statistical analysis. By using multi-objective optimization, the models of performance and cost assessment are built to evaluate the grinding performance and cost under different grinding conditions. In this way, the grinding performance and cost of different wheels can be quantitatively and qualitatively compared. With a comprehensive performance-cost analysis, the performance index of diamond wheels have been testified to be considerably higher than that of Al₂O₃ wheels even though their purchase cost is much higher than that of Al₂O₃ wheels.     

浅谈环行起重机车轮偏斜的测量

环行起重机是核电站核岛内重要的起重设备,车轮偏斜作为通用桥式起重机制造过程中的重要技术要求,是起重机的制造过程中重要的检验测量尺寸,文章介绍环行起重机车轮偏斜值的测量方法。对车轮偏斜的测量工作具有一定的参考价值。     

Analysis of the wheel/rail rolling contact fatigue of a high-speed train under the transient mechanism

The Rolling contact fatigue (RCF) damage of high-speed wheels is a main factor that affects railway safety. This paper presents a Finite element model (FEM) of high-speed transient rolling contact that considers kinetic parameters as initial conditions. This model is used to calculate wheel/rail RCF. With a CRH2 high-speed train as the research object, a head car model is established with the multibody dynamics software UM. The train is driven on a straight track at a speed of 300 km/h. Different contact geometric parameters, such as lateral displacement and attack angle, are obtained. A 3D high-speed transient elastic-plastic FEM of wheel/rail rolling contact is then developed by using ABAQUS with the initial dynamic contact geometric parameters. The actual geometries of the wheel tread and rail head as well as the elastic-plastic properties are considered in this model. This consideration makes the model highly suitable for solving 3D transient rolling contact behavior. The normal force, creep force, and contact area in the contact patch are solved and used in the fatigue model. Owing to the hunting movement of wheels, the wheel/rail force and lateral displacement change significantly at 0.2 and 0.5 s. The longitudinal and lateral creep force increase sharply with the increase in shear stress. The work states of the wheel/rail at 0.2 and 0.5 s easily reach the ratchet effect zone, and the fatigue index is large. The fatigue damage of the wheels is generally near the nominal rolling circle.     

600t高速铁路箱梁架桥机的三维有限元分析

应用国际上广泛使用的大型通用有限元分析程序Super SAP对600 t高速铁路箱梁架桥机JQ600进行了整体和局部应力计算及稳定性分析,其中关键部位的局部应力计算结果与实测结果接近.说明本文所使用的方法和技巧是有效的.这对开发更大吨位的高速铁路架桥机的力学计算有一定的指导意义.     

铁路钢轨缺陷伤损巡检与监测技术综述

我国高速铁路的快速发展给铁路钢轨基础设施的状态维护和安全保障带来挑战,综述了钢轨不同类型缺陷伤损的巡检与监测技术。回顾总结了国内外钢轨无损检测与监测技术的特点和局限性,以及钢轨在线巡检与监测仪器的应用情况。分析了多模态多物理集成传感与可视化成像检测、宏观与微观组织状态观测、无损检测与评估和健康监测集成融合,以及基于大数据管理的铁路钢轨快速巡检和实时监测等新技术研究进展,讨论了未来铁路钢轨缺陷伤损巡检及监测技术的发展趋势。