Near surface deformation of rails and wheels in a curve and during acceleration and braking

A hierarchical concept for describing the rolling/sliding contact of a wheel on a rail is proposed, which is developed to model the near surface deformation of the contacting partners depending on the vehicle system dynamics. In principal the vehicle dynamics simulation delivers the input for a static finite element model for the elastic-plastic rolling/sliding contact investigation. To include also more realistic rough surfaces in the calculations, which is absolutely necessary to predict the highly deformed surface layer as observed in wheels and rails, a further refinement of the mesh is necessary and performed. The output values of the static finite element model are now boundary conditions for the finite element micro-model. The results of this micro-model correspond well with the micro-structural investigations of wheel and rail surfaces.     

Tangential problem solution for non-elliptical contact areas with the FastSim algorithm

This article deals with the application of the FastSim algorithm to the solution of the tangential contact problem for non-elliptical contact areas. At first, the causes creating problems for the solution of non-hertzian contact areas with this algorithm shall be analyzed. Then, different currently existing methods shall be studied, analyzing their accuracy characteristics and computational cost to determine whether or not they are appropriate to use in dynamic simulations. Finally, a new strategy shall be proposed that, in the opinion of the authors, offers good characteristics of precision and computational cost.     

Prediction of wheel wear in urban railway transport: comparison of existing models

One of the most important maintenance costs in tramway transport comes from wear of wheel profiles. In the highly competitive railway market, the prediction of wear is then a major concern of the constructors. In this article, we present and compare four models well adapted to tramway conditions, involving contacts on the rolling tread and on the flange with very different sliding and pressure conditions. Moreover, all models can be implemented from the natural outputs of the railway simulation packages classically used in industry for the dynamics design of the vehicles. The first one, proposed by Jendel, is based on the well-known Archard's wear model. Enblom continues Jendel's approach by taking into account the contribution of wheel deformation on the sliding velocity. The last two models, developed by Zobory, and Pearce and Sherratt, determine the wear from the energy dissipation in the contact area. The models are first compared on a theoretical basis and, for that purpose, are rewritten in a common form. Two cases are distinguished: mild wear as arising on the rolling tread and severe wear as arising on the flange. The models are also compared in the practical case of an urban transport vehicle running on circular tracks with different curve radii. Although the models show equivalent trends according to the theoretical study, important discrepancies appear between estimated wear depths. All models are actually dependent on experimental coefficients and it is likely that they were estimated in different conditions. On the other hand, a reasonable agreement can be found in some particular conditions. As an example, Zobory's, Enblom's and Jendel's models are very close to each other in severe wear conditions. This work shows that a general and reliable model could probably be developed from all positive aspects of the existing ones.     

车辆驱动动力学安全控制策略的研究

借助于MATLAB／Simulink软件建立汽车的模拟模型及其故障分析结构模型，作为汽车自诊断控制的算法进行系统故障检测和故障评价，并通过驾驶试验来验证汽车模型模拟的准确性；同时把试验信号贮存在控制单元中，进行功能和性能诊断试验，识别车辆系统恶化状况和判别车辆系统安全可靠性。为车辆动力电子控制系统稳定性的性能判断与评估提供了一个理论基础。     

有直动式液压间隙调节器的气门机构的试验与计算分析

对一个有直动液压间隙调节器（ＨＬＡ）的气门机构进行了试验和动力学计算分析。实测了ＨＬＡ泄沉特性以确定ＨＬＡ模型中模拟泄漏的阻尼参数。为了获得气门机构的实测运动规律以验证计算结构和估算ＨＬＡ高压腔混气量，对该机构的气门加速度和ＨＬＡ高度变化量进行了动态测试。动力学计算结果和实测结果对比表明所建立的两种气门机构动力学计算模型都是可用的。分析计算结果对模型参数的敏感度。     

行星变速器动力学模拟程序

行星变速器在机构动力学的研究范畴内是一个比较简单的“线性约束系统”,本文利用这一特点,以角速度系数矩阵为基础,建立了行星变速器运动学微分方程的统一形式B_K~TJB_Kdω_d~K/dt=B_K~TM。尽管在换档过程中,系统的自由度在不断地变化,但常系数矩阵B_K只与结合的操纵件有关,它通过一个常数矩阵B线性变换得到。基于这一理论,作者调试成功了行星变速器动力学模拟通用程序,为深入分析行星变速器换档过程和行星变速器设计提供了一个手段。     

轮胎侧偏动力模型的非线性分析

轮胎径向变形与轮胎接地印迹长度呈非线性关系，从而导致轮胎侧偏力和回正力矩与车轮动载荷也是非线性关系。本文用一轮胎模型对这一现象进行了理论分析，并得到了与实验数据基本一致的结果。     

多体系统动力学分析的两大软件——ADAMS和DADS

对多体系统分析(机械系统仿真分析)领域中最广泛使用的两个软件ADAMS和DADS，从理论基础、组成模块、分析功能和建模元素等几个方面进行了对比，从而对二的特点有进一步的了解，便于选用最为适合的软件。最后，给出了二相应的应用实例。     

大跨度铁路悬索桥风—车—桥耦合动力分析

悬索桥虽跨越能力大但刚度较弱,在列车与风荷载的共同作用下易产生较大振动,影响桥上行车安全.为研究风荷载作用下列车通过铁路悬索桥时的车辆与桥梁动力响应及安全性,以轮轨密贴理论定义竖向轮轨作用力,以简化的Kalker蠕滑理论定义横向轮轨作用力,以静风力及抖振风力模拟作用在车辆和桥梁上的风荷载,建立简化的大跨度铁路悬索桥的风—车—桥耦合动力学模型,并给出基于系统间积分的风—车—桥迭代算法.运用该方法对强风条件下列车通过跨度(52+800+800+52)m悬索桥的行车安全性分析表明,系统间迭代算法具有较高的计算效率,仅经过几次迭代即可得到精度较高的计算结果;该大跨度悬索桥在桥面平均风速为25 m·s-1时,桥梁跨中竖向动位移较无风状态变化不大,而桥梁跨中竖向加速度及桥跨、桥塔横向动位移和加速度响应则较无风状态有大幅度增加,可见,动风荷载对风—车—桥系统的振动起到控制作用.     

重载铁路桥上无砟轨道动力学选型研究

为给孟加拉帕德玛大桥铁路连接线桥上无砟轨道结构选型提供依据,基于车辆-轨道耦合动力学理论,建立重载货车-无砟轨道-桥梁耦合动力学模型,分析不同轴重货车通过桥上不同类型无砟轨道时的动力响应。结果表明:随着列车轴重的增大,桥上无砟轨道部件的动力响应明显增大;从降低轨道结构位移的角度考虑,优先选取现浇板式无砟轨道和单层长枕埋入式无砟轨道等单层无砟轨道结构;从降低轨道与桥梁的接触应力及桥梁振动加速度的角度考虑,应优先选取单元板式无砟轨道和长枕埋入式无砟轨道等双层无砟轨道结构。重载铁路桥上无砟轨道选型应综合考虑桥上无砟轨道的动力特性、线路特点及其与相关专业的接口等因素综合确定,相关成果可为重载铁路桥上无砟轨道选型提供参考。