Elastic-plastic analysis of a rolling disk by finite elements

An elastic-plastic finite element method is employed to determine the stress distribution in a circular disk rolling on a rigid track and subjected to hub loads. This model can be assumed to represent a railroad wheel. Of particular interest are the stresses that exceed the initial yield limit near the point of contact. The material constitutive laws considered herein represent elastic-perfectly plastic and strain hardening materials that obey Mises' yield condition. It is shown that unloading of the previously yielded elements due to rotation can be easily handled by the direct stiffness tangent modulus approach. Total and plastic strains, and the plastic work in the disk model are given for the entire rolling history of the disk. It is also demonstrated that the disk will shake down to a purely elastic steady state for load values beyond the initial yield if the material of the disk exhibits even a small amount of strain hardening.     

基于ANSYS的轮轨摩擦滑动接触应力分析

以Hertz接触理论为依据,利用ANSYS建立2D有限元计算模型,模拟原地打滑、完全制动等轮轨滑动摩擦接触行为。分析了轮轨静接触和滑动接触时接触应力分布情况,研究了接触状态、轴重、滑动速度、载荷类型和钢轨轨顶圆半径对接触应力的影响。结合Hertz接触理论计算结果、剥离损伤理论和自激振动理论进行了轮轨损伤分析。     

Study on stress states of a wheelset axle due to a defective wheel

High magnitude impact loads caused by a defective wheel may excite various vibration modes of the wheelset, and contribute to adversely increases in the stress states of wheelset axle in high-speed conditions. In this study, the wheelset is treated as a flexible body using the finite element method, then integrated to a multi-body dynamic model of a high-speed train coupled with a flexible track slab model. Through this model the effects of wheel defects considering wheel flats and wheel polygonalizations on the stress states of wheelset axle are evaluated in terms of bending stresses of the wheelset axle. The damage tolerances of the wheelset axle are subsequently predicted using the NASGRO algorithm. The results suggest that the impact forces caused by wheel flats and wheel polygonalizations at the wheel-rail interfaces can result in the resonance vibrations of a wheelset and give rise to severe variations in dynamic stresses of the wheelset axle. The wheel defects-induced stress load cycles considerably contribute to the propagations of the initial crack in the wheelset axle, especially for the wheel polygonalization.     

Numerical analysis of rolling-sliding contact with the frictional heat in rail

Thermal damage caused by frictional heat of rolling-sliding contact is one of the most important failure forms of wheel and rail. Many studies of wheel-rail frictional heating have been devoted to the temperature field, but few literatures focus on wheel-rail thermal stress caused by frictional heating. However, the wheel-rail creepage is one of important influencing factors of the thermal stress In this paper, a thermo-mechanical coupling model of wheel-rail rolling-sliding contact is developed using thermo-elasto-plastic finite element method. The effect of the wheel-rail elastic creepage on the distribution of heat flux is investigated using the numerical model in which the temperature-dependent material properties are taken into consideration. The moving wheel-rail contact force and the frictional heating are used to simulate the wheel rolling on the rail. The effect of the creepage on the temperature rise, thermal strain, residual stress and residual strain under wheel-rail sliding-rolling contact are investigated. The investigation results show that the thermally affected zone exists mainly in a very thin layer of material near the rail contact surface during the rolling-sliding contact. Both the temperature and thermal strain of rail increase with increasing creepage. The residual stresses induced by the frictional heat in the surface layer of rail appear to be tensile. When the creepage is large, the frictional heat has a significant influence on the residual stresses and residual strains of rail. This paper develops a thermo-meehanical coupling model of wheel-rail rolling-sliding contact, and the obtained results can help to understand the mechanism of wheel/rail frictional thermal fatigue.     

曲线半径及轴重对轮轨摩擦功影响的研究

基于非Hertz滚动接触理论利用数值计算方法详细分析了静态接触情况下,轴重和曲线半径对轮轨接触质点间等效应力、接触斑粘滑区的分布、总滑动量和摩擦功的影响。分析计算表明,轴重增加引起轮轨接触质点间等效应力,接触质点间粘滑区的面积以及总滑动量的变化,同时对轮轨接触质点阍的摩擦功的变化有重要影响;小曲线半径处轮轨接触质点间的总滑动量,接触斑滑移区的面积以及摩擦功都明显增大,导致曲线上钢轨磨损加剧。因此曲线半径和轴重是影响轮轨滚动接触磨损的重要因素。     

车轮滑动时钢轨热机耦合有限元分析

利用有限元分析软件ABAQUS建立了轮轨接触热机耦合分析的热弹性平面应变有限元模型.模型中考虑温度对材料热物理参数的影响.分析了车轮滑动时不同摩擦因数和轴重对钢轨应力场分布的影响.结果表明,最大Von Mises等效应力发生在接触斑后半轴靠近接触区的边缘处,轮轨摩擦热影响区主要分布在接触表面,并随深度的增加其影响越来越小;当温升较大时,热物理参数随温度变化的影响应予以考虑;钢轨表面应力随摩擦因数和轴重增大而增大.     

On the Question of Monitoring Residual Stresses in Selectively Heat-Strengthened Rails

The question is considered of the relationship between the divergence of a longitudinal (400 mm) groove in the rail web, used as an indirect residual-stress–based rejection criterion, with internal stresses measured by acoustic strain gaging across the rail section. The internal stresses have also been evaluated in individual rail elements after cutting. A finite element simulation in the COMSOL Multiphysics software environment has been performed in order to establish connection between groove divergence and stresses. Results are presented for experimental measurements over 49 sections of different rails. The relationship is demonstrated between the stress level in rail elements and the level of stresses measured by an electromagnetic-acoustic structuroscope in an experiment on the side of the railhead. Based on the modeling and experimental results, an acoustoelastic technique is proposed for monitoring residual stresses in rails as an expert method with a rejection level of 80 MPa when sounding a rail section on the side of its head.     

基于AWB的驱动桥疲劳强度及寿命有限元分析

针对某型号整体式铸造驱动桥,在ANSYS WORKBENCH中建立起桥壳的有限元模型。最大垂直载荷作用下驱动桥的刚-强度分析结果表明,该驱动桥的刚度满足国家标准要求,圆弧过渡区及阶梯轴直径过渡区域应力较大,最大等效应力没有超过材料的屈服极限,桥壳不会出现断裂和塑性变形。驱动桥的疲劳寿命分析发现,该桥壳的疲劳寿命偏安全。     

Thermo-mechanical finite element analysis of a rail wheel

The rail wheel, which is acted upon by mechanical forces also experiences thermal stresses due to braking, during service. The coupled nature of these forces is analysed using a three-dimensional elasto-plastic finite element model. Contact stresses at the rail–wheel interaction location are analysed using a global–local approach on a three-dimensional elasto-plastic finite element model. The paper also brings out the size and shape of the plastic zone at the contact region. Commercial finite element code ABAQUS has been used for the analysis and SDRC’s I-DEAS has been used for modelling. American Association of Railroad’s standards, available for the purpose of analytical evaluation of the rail wheel, has also been critically evaluated in this work.     

An investigation into the effect of train curving on wear and contact stresses of wheel and rail

Some important papers concerning the studies on rail wear and wheel/rail contact stresses are briefly reviewed. The present paper utilizes a numerical method to analyze the effect of railway vehicle curving on the wear and contact stresses of wheel/rail. The numerical method considers a combination of Kalker's non-Hertzian rolling contact theory, a material wear model and a vertical and lateral coupling dynamics model of the vehicle/track. In the analysis, the important factors influencing on the wear and the contact stresses are, respectively, the curving speed, the curved track super-elevation and the rail cant. Compared to the present model, some concerned models and results in the published papers are in detail discussed. Through the detailed numerical analysis, it is found that the difference between the normal loads of the left and right of the wheelset increases linearly with increasing the vehicle curving speed. The material wear volume per length along the rail running surface has a tendency to grow. However, the variation of the maximum normal contact stress has a large fluctuation as the curving speed increases. The increase of the maximum contact stress depends greatly on not only the normal load but also the profiles of the wheel/rail. Increasing the track super elevation efficiently lowers the normal load difference of the left and right of the front wheelset, and the contact stresses and the wear. The rail cant has a great influence on the low rail wear of the curve track. An increase in rail cant results in a great increase in the low rail wear of the curved track, and a decrease in the outside rail wear. These conclusions are very useful in the maintenance of the track.     

飞机单腹板轮毂结构强度分析

建立飞机单腹板轮毂结构的有限元分析模型，考虑轮胎与地面，轮胎与轮毂、轮毂与轴之间的三维接触，轴承的可变形性和轮胎材料的超弹性特性，计算得到径向载荷和径侧向载荷作用下轮毂的应力和径向位移分布规律，加载剖面上的多点就变值与实验结果对比基本吻合，验证了模型的有效性，计算结果可用于改进轮毂的结构设计。     

Analysis of new method for vertical load measurement in the barycenter of the rail web by using FEM

Continuous method for measuring the forces between the wheel and rail is very important to monitor track loads. One of the usual methods is installing a strain gauge on the rail surface. Thus, strain gauge exposed to aggressive environment that makes it difficult for system to measure exclusively vertical force component and has complex installation operation. In this paper, strain measurement to assess the vertical load on cross section barycentric of rail and the lateral surface of rail web are studied. For this purpose, finite-element analysis was performed and the forces that exchange between wheel and rail in contact location were replaced with the moving loads that were applied to the railhead directly. Size of the effective contact patch was obtained from Hertz contact theory and patch switching time was considered short enough to reach an approximate continuous moving load. The results demonstrate the magnitude of strain in vertical direction is approximately same for the cross section barycentric and lateral surface of the rail web. However, the great advantage of measurement in the cross section barycentric of rail better distinguishes longitudinal and lateral strains from the vertical and also lateral load on a rail has less effect on vertical load measurement.     

钢轨踏面斜裂纹模拟再现试验研究

根据钢轨踏面斜裂纹的损伤特点和轮轨力与斜裂纹关系分析设计试验方案,在西南交通大学JD-1轮轨模拟试验机上,对广深高速铁路铺设的PD3热轧钢轨材料进行了斜裂纹损伤再现试验。试验结果表明,轮轨接触方式是钢轨斜裂纹产生和扩展的重要影响因素;轴重增加会增大轮轨接触应力,增加磨损量,加速接触疲劳现象的产生。     

无人机前起落架结构设计与有限元分析

为提升某型无人机前起落架抗弯和抗扭性能,减轻结构重量,设计了一种摇臂支柱式起落架结构。采用液压阻尼器+弹簧缓冲器结构形式,与机体连接采用对称支柱式限位连接结构,以起落架实际使用载荷为基础,分析仿真模型的载荷工况及边界条件,并运用ABAQUS软件对其进行有限元分析。计算结果表明,前起落架最大变形位于轮叉根部与机轮轮轴连接处,最大应力位于前起落架根部固支处,满足静强度要求。     

硬化深度对港口起重机车轮接触应力的影响

在建立港口起重机轮轨接触的三维实体模型的基础上，通过商业软件ANSYS建立了车轮材料不做硬化、硬化10mm、硬化25mm、全部硬化4种有限元模型；计算了这4种模型点接触和线接触2种轮轨接触模型的接触应力和接触面积，并与相应的赫兹理论值对比。通过对不同车轮硬化处理方式的接触应力和接触面积的比较，分析硬化处理对车轮接触的影响。     

材料特性对车轮疲劳强度的影响

研究材料非线性本构、非金属夹杂物、低温冲击功和断裂韧性对高速动车组车轮疲劳强度的影响。考虑弹塑性接触带钢轨车轮有限元分析模型,研究不同轮径下车轮轮辋应力分布规律。研究影响车轮疲劳强度的材料主要性能指标,研究夹杂物尺寸和许用应力、裂纹扩展门槛值的关系。研究断裂韧性和踏面剥离的关系、低温冲击功和车轮瞬间脆性破坏的关系。分析不同轮径和车轮疲劳强度的关系。     

万向节十字轴数值模拟及结构改进

万向节用于开窗作业主要起传递扭矩和轴向载荷作用,十字轴属万向节易断裂零件。利用有限元数值模拟方法,对十字轴受扭矩载荷进行分析,发现十字轴的应力集中现象主要集中在十字轴轴径有落差和两轴相贯的地方。通过对十字轴中间毛坯进行结构改进,并加大轴颈根部圆弧尺寸,发现应力集中现象得到明显改善,可有效提高十字轴可靠性。     

单侧钢轨波磨对两侧轮轨瞬态响应的影响分析

基于我国某地铁钢轨波磨的调研,采用显式有限元法建立了考虑车轮、车轴和钢轨连续体振动以及车辆、轨道高频结构振动的全轮对三维瞬态轮轨滚动接触模型,在时域内数值再现了轮对通过单侧钢轨波磨轨道段时的滚动接触行为,系统分析了单侧钢轨波磨对两侧轮轨瞬态响应的影响。相比于作者之前开发的半轮对滚动接触模型,该模型可将轮轨横向蠕滑和大自旋考虑在内。结果表明：地铁运行速度越高,波磨侧的不均匀磨损现象越严重;计算的五个速度中,波磨造成的瞬态激励在30和120 km/h时更易传递至无波磨侧,进而促进无波磨侧钢轨萌生波磨;轮对越是向波磨侧横移,波磨侧不均匀磨损越严重,但无波磨侧不均匀磨损逐渐降低,即相较于直线段,横移更大的曲线段上的外侧钢轨波磨更不易引发另一侧钢轨的波磨。     

纳米结构WC/12Co涂层精密平面磨削表面残余应力有限元模拟与试验

对金刚石砂轮精密平面磨削纳米结构WC/12Co涂层的磨削表面残余应力进行有限元模拟,忽略相变影响,基于ANSYS平台,利用ANSYS参数设计语言完成建立模型、给定材料属性、划分单元、加载和求解整个过程。对纳米结构WC/12Co涂层表面磨削残余应力进行试验研究,通过改变磨削条件得到不同磨削条件下残余应力的变化规律。将试验结果与相同磨削条件下的有限元模拟结果进行对比,发现试验结果与有限元模拟结果是一致的,证明了有限元模型的正确性。     

地铁线路曲线段磨耗状态下轮轨滚动接触有限元分析

基于城市轨道交通曲线段不同磨耗程度的典型钢轨和车轮的实测型面,利用有限元分析软件ANSYS建立曲线段轮轨三维弹塑性接触有限元模型,对三种不同轮轨磨耗型面匹配工况下的地铁车辆的曲线通过性能以及轮轨接触应力进行计算分析,分析不同磨耗状态下车轮和钢轨接触时的接触应力和轮轨应力的分布状态,并研究其对钢轨磨耗的影响。发现钢轨使用初期,由于轮轨廓形不一致,轮轨间易出现应力集中,应力集中部位易出现磨损;随着钢轨侧磨的增加,轮轨接触状态逐渐由一点接触变为两点接触,且接触点的塑性变形部分和弹性部分的过渡区间易出现裂纹;两点接触状态下,外侧轨距角处接触面积及应力集中区域远大于钢轨侧面部分,轨距角易出现较大的接触压力,易加速钢轨磨耗与疲劳伤损的产生。