不同焊缝类型对宽轮距转向架构架疲劳分析的影响

转向架是单轨车辆核心的部件之一,承担着车辆的牵引、制动和承载作用,直接影响到车辆运行的安全性和可靠性。其中构架又是转向架的承载主体,传递并衰减轮轨与车体的振动。宽轮距转向架构架通过焊接和大量螺栓连接,事实上,在复杂的动载荷作用下,疲劳破坏主要从焊缝和螺栓连接处开始。对于焊接结构,由于焊接接头部位存在较大的应力集中,且常伴随有各种焊接缺陷,因而是最容易发生疲劳破坏的区域。所以焊缝结构疲劳分析及优化在设计阶段尤为重要。     

DAMAGE TOLERANCE ANALYSIS ON HOLLOW AXLES OF HIGH SPEED MOTOR TRAINS

According to the rules of UIC515-3, the service loads of the axles are defined, which include some different loads cases as follows： the static loads; the impact loads resulted from running through the rail joints and unevenness rails; the loads through curves and from braking. Through the calculating and analysis, the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China. At the same time, the fatigue crack growth of hollow axles is studied, and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed. On the basis of the linear elastic fracture mechanics theory, the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied. Associated with fatigue crack propagation equation and the corresponding crack propagation threshold, the crack propagation characteristics under different shapes are calculated. Then the running distances are educed with different shapes propagating to the critical length, and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.     

汽车钢圈疲劳寿命研究

汽车车轮是介于轮胎和车桥之间承受整车负荷的旋转件,是汽车行驶系统中重要的安全部件。钢圈的主要破坏形式是循环载荷产生的疲劳破坏,它是导致钢圈破坏的主要原因。文中研究了轮辐与轮辋的装配过盈量、接触量长度及轮辐外圆的加工状态对钢圈径向疲劳寿命的影响。结果表明,当接触量长度一定时,钢圈的疲劳寿命随着过盈量的增加而增大;当过盈量一定时,随着接触量长度的增加,钢圈的疲劳寿命逐渐增大,钢圈的最大疲劳寿命大于100万次。轮辐外圆未车削时,在较大的过盈量下,钢圈可达到较高的疲劳寿命。     

Investigation into the vibration of metro bogies induced by rail corrugation

The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel–rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.     

Fatigue life estimation of MD36 and MD523 bogies based on damage accumulation and random fatigue theory

Bogies are one of the multifunctional parts of trains which are extremely subjected to random loads. This type of oscillating and random excitation arises from irregularities of the track including rail surface vertical roughness, rail joints, variance in super-elevation, and also wheel imperfections like wheel flats and unbalancy. Since most of the prementioned sources have random nature, a random based theory should be applied for fatigue life estimation of the bogie frame. Two methods of fatigue life estimation are investigated in this paper. The first approach which is being implemented in time domain is based on the damage accumulation (DA) approach. Using Monte-Carlo simulation algorithm, the rail surface roughness is generated. Finite element (FE) model of the bogie is subjected to the generated random excitation in the first approach and the stress time histories are obtained, and consequently the fatigue life is estimated by using the rain-flow algorithm. In the second approach, the fatigue life is estimated in frequency domain. Power spectral density (PSD) of the stress is obtained by using the FE model of the bogie frame and the fatigue life is estimated using Rayleigh technique in random fatigue theory. A comprehensive parametric study is carried out and effects of different parameters like the train speeds and level of the rail surface vertical roughness on the estimated fatigue life are investigated. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Davood Younesian received his MSc and PhD in Mechanical Engineering, both from Sharif University of Technology, Iran. He joined the Iran University of Science and Technology in 2005 as an Assistant Professor in the School of Railway Engineering. Dr Younesian’s research area is mainly focused on non-linear and random vibrations, optimal control of vibrations, dynamics and vibration of structures and railway vehicle systems. He has published more than 75 papers in international journals and conference proceedings in the areas of his research. Ali Solhmirzaei received his BSc in Railway Engineering (Rolling Stock) from Iran University of Science and Technology and his MSc in Mechanical Engineering from K.N.T University of Technology, Iran. His research is mainly focused on finite elements, railway vehicle dynamics and fatigue analysis of railway structures. Alireza Gachloo received his BSc in Railway Engineering (Rolling Stock) from Iran University of Science and Technology, Iran. His research is mainly focused on random vibration, railway vehicle dynamics and random fatigue.     

Fatigue life evaluation of mechanical components using vibration fatigue analysis technique

Unit brackets attached on a cross member and subjected to random loads often fail due to self-vibration. To prevent such failures, it is necessary to understand the fatigue failure mode and to evaluate the fatigue life using test or analysis techniques. The objective of this study is to develop test specifications for components, which are applicable to predict fatigue life at the stage of initial product design, for the unit brackets by using a vibration fatigue technique. For this objective, the necessity of a fatigue analysis considering resonant effect was reviewed. Also, a series of vibration fatigue analyses were carried out by changing the acceleration’s direction and magnitude. Then, a methodology was proposed to determine the optimum vibration fatigue test specification of the component, which gives an equivalent failure mode with the vehicle test condition.     

Fatigue analysis of the main frame of over head transportation vehicles using flexible multibody dynamics

The industrial over head transportation vehicle is a guided railway vehicle that is attached overhead and transports cargo, hoisting it up and down from the factory ceiling. The vehicle is widely used in many industries, such as automobile and liquid crystal display (LCD), because it can carry freight very safely and quickly to destinations. This kind of freight transportation usually operates for several months to a few years, carrying large amounts of products. Accidently, the vehicle often fails during operation because of a part’s plastic deformation from large loads. Furthermore, periodic dynamic loads cause fatigue accumulation, which leads to OHT failure. This failure is directly connected to significant economic loss during mass production processes. Therefore, the prediction of fatigue life for the important parts becomes an important task. In this study, the fatigue life of an OHT main frame was calculated and predicted by using a flexible multibody dynamic model. The development of a flexible multibody dynamic model and the procedure of fatigue life prediction were presented. To predict the fatigue lives of parts of interest, the prediction procedure required three kinds of data: Dynamic stress time history from a dynamic analysis, material properties of the parts, and stress-life curves of the parts. Using a finite element model and a multibody model, a flexible multibody model was developed. To ensure the reliability of the model, displacement and strain measurement tests were conducted. After verification of the reliability, the fatigue life of the main frame was predicted.     

某无人机用涡喷发动机主轴疲劳寿命计算

涡喷发动机主轴所承受载荷十分复杂,扭矩、轴向力、离心载荷和陀螺力矩等载荷共同作用于主轴,在高温区还承受热负荷。在这些交变载荷共同作用下,疲劳断裂失效是其主要失效模式。根据无人机的任务剖面,编制该无人机用涡喷发动机主轴的疲劳载荷谱;并用工程估算方法得到该涡喷发动机主轴的S-N曲线,基于ANSYS建立有限元模型并进行疲劳寿命分析,给出了该涡喷发动机主轴的寿命。     

列车车辆垂向主动悬挂的最优预见控制研究

以四轴客车为研究对象,建立了四轴客车车辆的6自由度垂向动力学模型,并通过设计最优预见控制器来抑制车辆系统的垂向振动,研究结果表明采用最优预见控制策略能够降低车辆的垂向振动响应,获得较快的系统响应速度,达到满意的隔振效果。     

Study on determination of durability analysis process and fatigue damage parameter for rubber component

Rubber components, which have been widely used in the automotive industry as anti-vibration components for many years, are subjected to fluctuating loads, often failing due to the nucleation and growth of defects or cracks. To prevent such failures, it is necessary to understand the fatigue failure mechanism for rubber materials and to evaluate the fatigue life for rubber components. The objective of this study is to develop a durability analysis process for vulcanized rubber components, that can predict fatigue life at the initial product design step. The determination method of nonlinear material constants for FE analysis was proposed. Also, to investigate the applicability of the commonly used damage parameters, fatigue tests and corresponding finite element analyses were carried out and normal and shear strain was proposed as the fatigue damage parameter for rubber components. Fatigue analysis for automotive rubber components was performed and the durability analysis process was reviewed.     

低幅载荷对汽车前轴疲劳寿命影响的试验研究

为了探讨基于载荷特性的汽车结构件轻量化设计理论与方法，采用汽车前轴实物物理试验的方法，比较系统地研究某汽车前轴在低幅交变载荷作用下结构疲劳寿命的变化趋势，发现在低于疲劳极限的低幅应力区内存在一个强化载荷区。用强化载荷区内的不同载荷对前轴进行预锻炼，前轴的疲劳寿命有不同程度的提高。既使在高低载荷交替作用的条件下，低载强化效果依然存在。结构的寿命由强度衰减速率和强度提高速率共同决定，而不是仅由损伤决定。     

基于轮胎六分力的某商用车车架疲劳分析

实验以某重型商用车车架为研究对象,在汽车的3个车轴上共安装6个六分力仪,并在定远试验场多种路况下进行实车测试,获得车轮轮心处六分力。在HyperMesh中对车架进行有限元建模并应用惯性释放理论获得车架的单位载荷应力场分布。在ADAMS中建立整车刚柔耦合动力学模型,并将实车测试获得的轮心六分力导入模型中进行仿真,求得车架与悬架接附处的载荷谱。结合车架单位载荷应力场分布、车架与悬架接附处的载荷谱及车架材料的应变（ε）-疲劳寿命（N）曲线,根据线性累积损伤理论,使用nCode软件对车架进行疲劳仿真分析,分析结果表明该车架可靠寿命符合国家相关安全规定,满足设计要求。该仿真结果也被试验所验证。     

A fatigue and low-energy shock-based approach to predict fatigue life

A product that is characterized by fatigue-induced failure always suffers from complex fatigue loads, and the damage caused by fatigue loads accumulates with time. The existence of shocks not only directly increases the risk of failure but also affects the magnitude of damage caused by fatigue loads. This study analyzes the reliability of a product when fatigue loads and shocks are both involved. The features of fatigue damage and shock damage are investigated, and the coupling relationship between them is discussed. With assumptions of high cycle fatigue and low-energy shocks, the effect of shocks on fatigue damage is expressed as the degradation of the ultimate strength of the product. An overall reliability model with fatigue and shock failures is developed. Two conditions are considered for the reliability model: shocks with fixed period and shocks with a homogeneous Poisson process. Three important cumulative damage theories are adopted. An engineering case of actuator cylinder is provided to demonstrate the proposed approach.     

随机振动环境下结构的疲劳失效分析

讨论了随机振动响应的统计特性分析、结构响应的动应力与常规疲劳载荷的关 系,如何将结构响应动应力等价为常规的静力疲劳载荷,利用Ｓ－Ｎ曲线和名义应 力法对结构寿命的估算方法等。完成了用功率谱密度表示的随机振动载荷作用下悬 臂板结构的响应分析以及疲劳寿命估计。     

基于线性疲劳累计损伤橡胶悬置疲劳寿命预测研究

橡胶元件疲劳寿命的有效预测是其设计开发过程中的重要环节。引入橡胶元件线性疲劳累计损伤原理,提出张量形式橡胶疲劳寿命公式,且根据橡胶材料的实际承载工况提出其失效标准。依据橡胶材料的承载变形可简化为单轴拉伸及简单切应变,设计用于承载拉伸载荷的哑铃型橡胶试柱和承载剪切载荷的环形橡胶试柱,并实测疲劳寿命数据,以最小二乘法原理拟合拉伸与剪切的疲劳寿命函数公式。以车用变速箱悬置与发动机后悬置为疲劳寿命预测研究对象,通过分析其承载位移载荷时的应变张量,利用张量形式的疲劳寿命预测公式预测两种悬置在两种典型工况下的疲劳寿命。结果发现,橡胶材料的拉伸疲劳寿命曲线与简单剪切疲劳寿命曲线的变化趋势一致、形状类似、拟合函数幂指数十分接近;张量形式的疲劳寿命预测公式可有效地预测橡胶悬置的疲劳寿命。     

轮胎疲劳失效研究综述

轮胎寿命对车辆行驶安全性影响巨大,而轮胎失效方式主要是疲劳失效.针对轮胎的疲劳失效,综述国内外疲劳失效的几种研究方法的特点和应用状况,认为裂纹扩展方法为主要的研究方法;而在基于该方法的研究中,疲劳失效评价指标的合理确定,直接影响到轮胎疲劳寿命的评价;疲劳寿命预报的模型分析技术也是目前轮胎失效研究亟待解决的技术难题之一.通过对目前所使用的评价指标的相关文献和理论调查,指出采用断裂能指标对寿命的预测比其他指标更合理.在对比了目前用来建立疲劳寿命预报模型的分析技术后,指出基于裂纹扩展方法,结合考虑温度效应的断裂能评价指标,并采用EDT分析技术建立疲劳寿命预报模型,预测轮胎疲劳寿命,将是分析轮胎疲劳失效比较有效的途径.     

应用对数累积损伤理论预测输弹弹簧疲劳寿命

本文在失效分析的基础上研究了某中口径自动舰炮输弹弹簧的疲劳累积损伤规律,应用对数累积损伤理论给出了计算其疲劳寿命的半经验公式,并讨论了应用对数累积损伤规律预测疲劳寿命的一般程序。     

某车型横向稳定杆的疲劳可靠性分析

横向稳定杆能有效预防车辆的侧翻,对保证汽车安全行驶起着重要作用,因此估算稳定杆的疲劳寿命尤为必要.目前有限元分析已成为一种获得零部件力学特性的有效且可靠的方法,所以借助有限元软件,为横向稳定杆的疲劳寿命估算及寿命值的分布提供了技术支持.为此首先建立该种车型稳定杆的参数化模型,并对其进行疲劳寿命的估算并在此基础上进行疲劳可靠性分析,得到疲劳寿命的分布及累积概率密度函数曲线等.最后对照稳定杆疲劳试验的寿命要求对疲劳可靠性分析结果进行了分析.     

汽车前轴低载强化三维曲面方程

通过对不同等级低幅载荷对某汽车前轴疲劳强度影响的试验研究，证实一定范围内的低幅载荷对结构件的强化效果确实存在，并且是比较显著的，在物理试验结果的基础上，通过数值试验和正交多项式回归的方法，得到该前轴在低幅交变载荷作用下的三维强化曲面方程，这为正确评估该前轴使用中的强度变化规律提供了理论和技术依据，为建立基于使用载荷和结构疲劳强度特征的结构轻量化设计理论与方法进行了有益的探索。     

电液控制全轮转向系统

多轴车辆在后桥增设电控液压转向系统,可实现整车的全轮转向,对整车性能有较大提升。但由此也引出几个问题:一是车辆变成全轮转向后,原车的前桥转向机构是否需要重新设计;二是当后桥车轮不需要转向或者当电控液压转向系统失效时,如何保证后桥车轮处于直行位置且一直保持在直行位置;三是全轮转向具有多种转向模式,模式之间如何平稳的进行切换。这些问题的合理解决决定着全轮转向系统的性能。以四轴车辆为研究对象,从机械、液压、电控三方面就提出的三个问题进行着重分析。