基于接触变形量修正模型的圆锥滚子轴承刚度计算

轴承接触受力以及刚度计算是一个非线性力学问题,文章基于修正的Palmgren模型对圆锥滚子轴承的滚子接触力和接触刚度进行了计算。通过对所有滚子的接触力、力矩以及其对轴承内外圈造成的接触变形的计算和叠加,推导了圆锥滚子轴承的刚度模型。为了验证模型,建立网格数量多、精度较高的圆锥滚子轴承有限元模型,计算了滚子以及外圈的应力分布情况,通过对有限元计算结果接触力和接触变形量的提取,识别了轴承刚度并与文章所建立模型的计算结果进行了对比,结果表明,所建立模型是准确的。     

基于竖向加速度响应的机场道面平整度评价及IRI标准反演

为了制定科学的机场道面平整度评价标准,提出一种基于竖向加速度响应的机场道面平整度评价方法并反演IRI标准。综合考虑飞机的竖向运动、俯仰和侧倾转动,建立6自由度的飞机整机动力学模型及振动平衡方程,并从飞机轮胎的几何滤波效应出发,采用"刚性滚子"轮胎接触模型的有效路形表征不平整道面;同时,构建飞机驾驶员、前舱位、后舱位和重心处的竖向加速度及其最大响应的计算模型,并采用Simulink仿真模块进行快速求解。以某代表C类飞机为例,在服从高斯分布的随机道面激励及不同滑行速度下,综合分析4个代表部位的最大竖向加速度响应的分布特性,建立其对应的非线性回归模型,并以波音公司疲劳标准为据,反演机场道面平整度的IRI标准值。结果表明:与现有标准相比,反演的IRI标准值更为宽松,且跑道的平整度标准比滑行道更严格,与实际中机场道面的平整度评价相吻合。     

车轮荷载下土壤静力学特性分析

利用有限元软件ANSYS建立三维有限元模型,模拟车轮和土壤的静态接触,进行非线性有限元分析,研究车轮荷载下土壤的静力学特性。采用基于Drucker-Prager的弹塑性模型来模拟真实土壤,并考虑摩擦作用。分别采用刚性轮模型和超弹性轮胎模型模拟车轮,并将2种情况进行对比。结果表明：在车轮荷载作用下,土壤的竖向位移和等效应力在轮胎与土壤接触的区域最大;土壤的竖向位移和等效应力随土壤深度的增加而减小;土体在刚性轮作用下的变形和应力要远大于其在超弹性轮作用下的值,表明虽然刚性轮几何形状简单,模型设置容易,但是与超弹性轮胎模型相比,这种模拟精确度低。     

基于环模型的轮胎有限元建模与仿真研究

为了提高仿真模型的计算效率,基于环模型理论系统研究了轮胎二维有限元模型的建模技术、参数确定方法和轮胎包容特性分析技术.从试验与仿真结果对比分析可知,利用有限元方法基于轮胎REF模型建模,在对轮胎胎侧弹性进行非线性模型修正后,得到的轮胎低速滚动仿真结果与试验结果基本吻合,验证了轮胎模型的有效性,同时为车辆一地面系统虚拟试验提供了一种实时高精度的轮胎面内特性仿真建模方法.     

动态载荷下轮胎侧偏特性的理论及试验研究

提出了在动载和时变印迹长度下轮胎的接触历程概念,导出了计算动载时轮胎接地印迹内各点接触历程的入迹方程,阐明轮胎动载侧偏力学特性建模机理,克服了动载侧偏特性理论建模的一个基本障碍,建立了考虑胎体平移弹性小幅动载时的理论模型,并提出了轮胎动载侧偏特性的半经验模型,进行了相应的试验研究,给出了试验结果与模型计算结果的比较。     

子午线轮胎静态接触有限元分析及试验研究

对子午线轮胎195／60R14进行了三维非线性有限元分析及试验研究。在有限元模型中考虑了轮胎的几何非线性、材料非线性、轮胎与轮辋过盈配合以及轮胎接触非线性。得出了轮胎与地面接触过程中轮胎的变形情况、接触压力分布、载荷-变形关系等结果。采用连续加载、卸载方式，开展了轮胎准静态负荷试验。实时记录了试验中轮胎受力与变形关系，并采用压力敏感膜测量了轮胎接地区域内的压力分布状况。计算结果和试验结果符合较好。     

圆锥滚子轴承负荷分布计算

给出了圆锥滚子轴承负荷分布的计算方法，建立了轴承系统承载运行是的平衡方程，提出了求解方程的方法，形成了较原圆锥滚子轴承负荷分布计算模型，为建立轴承几何设计与性能分析交互式优化设计系统奠定了基础。     

基于车-桥耦合动力作用的车辆与桥梁力学行为

为研究车-桥耦合动力作用下的车辆与桥梁力学行为,基于ABAQUS有限元软件建立二自由度四分之一车辆模型和简支桥模型.车辆模型考虑橡胶轮胎超弹性,桥面铺装层考虑沥青混合料黏弹性.基于轮胎与桥面铺装层接触关系,建立车-桥耦合动力模型,采用中心差分法和有限元理论求解车辆和桥梁时域响应.结果表明:通过与现场桥面铺装层上面层跨中...     

悬挂也智能

在汽车发明之后的20多年里。汽车悬挂系统一直沿用马车的弹性钢板结构，其效果可想而知。直N1908年，螺旋弹簧的出现为汽车悬挂系统革新提供了新途径。但是当时工程师们对于这样的新事物产生了分歧：第一种意见主张安装刚性较大的螺旋弹簧，以使车轮保持着与路面接触的倾向，提高轮胎的抓地能力。但是这样的弊端是乘坐汽车时有较强烈的颠簸感觉。     

四轮随机输入下的汽车振动的计算机模拟(下)

四、汽车激励的确定欲求出系统的输入,必须对汽车的路面输入进行有效的描述。四轮输入下的三维模型优于二维模型,这是由于它能反映侧倾振动,使汽车的输入更接近于实际。在模型中,轮胎与路面是点接触的,而实际上是小块的面接触,且有跳动现象,这些都有一定的滤波作用,对不同的汽车也各不相同。为了补偿轮胎的包络作用,在计算中应该用有效路形。获得有效路形的方法是,在选定的路段上,汽车以匀速行驶,记录四个轴头的响应,     

Railway ground vibrations induced by wheel and rail singular defects

Railway local irregularities are a growing source of ground-borne vibration and can cause negative environmental impacts, particularly in urban areas. Therefore, this paper analyses the effect of railway track singular defects (discontinuities) on ground vibration generation and propagation. A vehicle/track/soil numerical railway model is presented, capable of accurately predicting vibration levels. The prediction model is composed of a multibody vehicle model, a flexible track model and a finite/infinite element soil model. Firstly, analysis is undertaken to assess the ability of wheel/rail contact models to accurately simulate the force generation at the wheel/rail contact, in the presence of a singular defect. It is found that, although linear contact models are sufficient for modelling ground vibration on smooth tracks, when singular defects are present higher accuracy wheel/rail models are required. Furthermore, it is found that the variation in wheel/rail force during the singular defect contact depends on the track flexibility, and thus requires a fully coupled vehicle/track/foundation model. Next, a parametric study of ground vibrations generated by singular rail and wheel defects is undertaken. Six shapes of discontinuity are modelled, representing various defect types such as transition zones, switches, crossings, rail joints and wheel flats. The vehicle is modelled as an AM96 train set and it is found that ground vibration levels are highly sensitive to defect height, length and shape.     

用于公路车-桥系统振动分析的精细化轮胎模型

为了解决当前公路车桥耦合振动模型中轮胎模型过于简化、车轮-路面接触力与桥梁响应计算结果不够精确的问题,提出了一种精细化轮胎模型.首先基于车辆橡胶轮胎的几何、力学特征,建立了径向弹簧力学模型并进行了理论推导;然后考虑轮胎与路面接触面的刚度分布特征和高速状况下轮胎的惯性力,提出了轮胎接触面分布刚度的计算方法,保证了轮胎接触...     

High-speed wheel/rail contact determining method with rotating flexible wheelset and validation under wheel polygon excitation

A rotating flexible wheelset model is developed and integrated into a vehicle/track dynamic model. Flexible wheelset modes with natural frequencies less than 1000?Hz are considered in the wheelset modelling. An innovation of the paper is that wheel/rail rolling contact calculation considers the effect of the wheelset flexibility and the rotating effect. By introducing two half dummy rigid wheelsets the rolling contact between the flexible wheelset and the two rails can be transformed to that between a rigid wheelset and the rails. As an extension application, the wheel OOR (Out-Of-Round) wears with the 11th, 15th, and 17th orders are used to the vehicle system dynamic model with rigid, flexible and rotating-flexible wheelset model. The results of the three models are compared to study the influence of wheelset flexibility and rotation. The ‘online searching contact method’ developed in this paper is compared with the traditional contact method with considering the rotating flexible wheelset. And then a measured OOR is used to excite the rotating flexible wheelset, the response of which is analysed and verified.     

Investigation of the effects of sleeper-passing impacts on the high-speed train

The sleeper-passing impact has always been considered negligible in normal conditions, while the experimental data obtained from a High-speed train in a cold weather expressed significant sleeper-passing impacts on the axle box, bogie frame and car body. Therefore, in this study, a vertical coupled vehicle/track dynamic model was developed to investigate the sleeper-passing impacts and its effects on the dynamic performance of the high-speed train. In the model, the dynamic model of vehicle is established with 10 degrees of freedom. The track model is formulated with two rails supported on the discrete supports through the finite element method. The contact forces between the wheel and rail are estimated using the non-linear Hertz contact theory. The parametric studies are conducted to analyse effects of both the vehicle speeds and the discrete support stiffness on the sleeper-passing impacts. The results show that the sleeper-passing impacts become extremely significant with the increased support stiffness of track, especially when the frequencies of sleeper-passing impacts approach to the resonance frequencies of wheel/track system. The damping of primary suspension can effectively lower the magnitude of impacts in the resonance speed ranges, but has little effect on other speed ranges. Finally, a more comprehensively coupled vehicle/track dynamic model integrating with a flexible wheel set is developed to discuss the sleeper-passing-induced flexible vibration of wheel set.     

Vertical random vibration analysis of vehicle–track coupled system using Green's function method

A vertical vehicle–track coupled dynamic model, consisting of a high-speed train on a continuously supported rail, is established in the frequency-domain. The solution is obtained efficiently by use of the Green's function method, which can determine the vibration response over a wide range of frequency without any limitations due to modal truncation. Moreover, real track irregularity spectra can be used conveniently as input. The effect of the flexibility of both track and car body on the entire vehicle–track coupled dynamic response is investigated. A multi-body model of a vehicle with either rigid or flexible car body is defined running on three kinds of track: a rigid rail, a track stiffness model and a Timoshenko beam model. The results show that neglecting the track flexibility leads to an overestimation of both the contact force and the whole vehicle vibration response. The car body flexibility affects the ride quality of the vehicle and the coupling through the track and can be significant in certain frequency ranges. Finally, the effect of railpad and ballast stiffness on the vehicle–track coupled vibration is analysed, indicating that the stiffness of the railpad has an influence on the system in a higher frequency range than the ballast.     

A numerical model of a HIL scaled roller rig for simulation of wheel–rail degraded adhesion condition

Scaled roller rigs used for railway applications play a fundamental role in the development of new technologies and new devices, combining the hardware in the loop (HIL) benefits with the reduction of the economic investments. The main problem of the scaled roller rig with respect to the full scale ones is the improved complexity due to the scaling factors. For this reason, before building the test rig, the development of a software model of the HIL system can be useful to analyse the system behaviour in different operative conditions. One has to consider the multi-body behaviour of the scaled roller rig, the controller and the model of the virtual vehicle, whose dynamics has to be reproduced on the rig. The main purpose of this work is the development of a complete model that satisfies the previous requirements and in particular the performance analysis of the controller and of the dynamical behaviour of the scaled roller rig when some disturbances are simulated with low adhesion conditions. Since the scaled roller rig will be used to simulate degraded adhesion conditions, accurate and realistic wheel–roller contact model also has to be included in the model. The contact model consists of two parts: the contact point detection and the adhesion model. The first part is based on a numerical method described in some previous studies for the wheel–rail case and modified to simulate the three-dimensional contact between revolute surfaces (wheel–roller). The second part consists in the evaluation of the contact forces by means of the Hertz theory for the normal problem and the Kalker theory for the tangential problem. Some numerical tests were performed, in particular low adhesion conditions were simulated, and bogie hunting and dynamical imbalance of the wheelsets were introduced. The tests were devoted to verify the robustness of control system with respect to some of the more frequent disturbances that may influence the roller rig dynamics. In particular we verified that the wheelset imbalance could significantly influence system performance, and to reduce the effect of this disturbance a multistate filter was designed.     

某重卡动力总成悬置系统隔振分析方法研究

为研究动力总成悬置系统隔振分析方法,论文以某重卡为研究对象,建立整车刚柔耦合多体动力学模型,并分别将柔性车架和刚性车架整车模型仿真结果与试验结果进行对比,最大误差分别为8.9%和25.1%,表明柔性车架整车模型与试验结果更为接近,能够用于动力总成隔振率的计算。为了简化分析过程,论文研究了基于柔性车架整车模型的3种简化方法,结果表明简化模型隔振率与试验结果相差最大为12.3%,与简化前相比隔振率相差最大为5.34%,因此,在车辆设计初期,没有实车及详细整车参数的条件下,利用简化后的模型可用于隔振率的仿真计算。该研究为动力总成隔振率计算提供了一定的理论指导,具有重要的工程应用价值。     

An Investigation into Stick-Slip Vibrations on Vehicle/Track Systems

A model for the numerical simulation of vehicle/track interaction and stick-slip vibration is presented. A finite element model is developed to calculate vertical contact forces. These forces are then coupled through the contact patch into a non-linear time-domain model by which the stick-slip vibration behaviour of a wheel-rail system is analysed. The investigation suggests that stick-slip vibration may occur if a vehicle which has a maligned or an initial 'wind-up' wheeiset meets a vertical irregularity or contaminants on the track.     

An Investigation into Stick-Slip Vibrations on Vehicle/Track Systems

SUMMARY

A model for the numerical simulation of vehicle/track interaction and stick-slip vibration is presented. A finite element model is developed to calculate vertical contact forces. These forces are then coupled through the contact patch into a non-linear time-domain model by which the stick-slip vibration behaviour of a wheel-rail system is analysed. The investigation suggests that stick-slip vibration may occur if a vehicle which has a maligned or an initial ‘wind-up’ wheeiset meets a vertical irregularity or contaminants on the track.     

Experimental investigations on the damping effect due to passengers on flexural vibrations of railway vehicle carbody and basic studies on the mimicry of the effect with simple substitutions

The effect of passengers on a railway vehicle is usually considered as additional mass in designing a carbody. However, previous studies by means of stationary excitation tests or running tests using actual vehicles indicate that passengers behave not as mass but as damping. In this paper, the authors examined the passengers' damping effect under controlled excitation conditions on a roller rig through a series of excitation tests using a commuter-type vehicle. Large and multi-modal reductions of flexural vibrations of the carbody were observed when passengers existed. Influences of the number of passengers, distributions and postures of passengers were investigated. The authors also tried to mimic the damping effect by passengers using flexible tanks filled with fluids. Three kinds of fluids which have different viscosities have been tested. As a result of the excitation tests, good vibration reduction effects were observed by applying those tanks, and it has been found that the flexible tanks filled with fluids bring about vibration reduction effect (including multi-modal reduction) which is equal to or rather better than the case of similar mass of passengers in the carbody; the difference of viscosity gave little affect on the damping abilities. From these measurement results, a possibility of realising effective damping devices against flexural vibrations of railway vehicle carbodies representing passengers damping effect, in a simple, economical and environmental friendly way, has been demonstrated.