轨道不平顺导致的车桥耦合振动分析

研究目的：轨道不平顺常常是激起车桥系统耦合振动的主要因素之一，通过研究轨道不平顺导致的车桥耦合振动规律，为铁路桥梁精确设计提供理论依据。 研究方法：以H．Hamid等人提出的轨道不平顺功率谱密度为例，构造了时域内的轨道随机不平顺函数。以轨道不平顺样本函数为激振源，通过求解车桥系统耦合振动微分方程，分析铁路桥梁在列车荷载作用下的动力响应规律。 研究结果：计算了广西红水河铁路斜拉桥在列车通过时的动力响应，给出了不同车速及不同不平顺样本函数情况下桥梁主跨中点横向位移时程曲线。 研究结论：桥梁结构动力响应主要随车速及不平顺样本函数的不同而变化，且有较大的随机性。对于广西红水河铁路斜拉桥，桥梁主跨中点的最大横向位移一般在车速为75～95km／h时达到最大。     

轨道不平顺激励下车辆-桥梁垂向随机振动方差解法

提出时滞多维非白噪声轨道不平顺激励下车辆-桥梁垂向随机振动的时域分析方法。采用白噪声滤波法模拟单轮对下的不平顺,在宽频带内识别滤波器参数以实现波长选择功能。基于Pade近似构造累次时滞滤波器以反映各轮对下不平顺之间的时滞关系。结合成型和时滞滤波器,构造以一致白噪声为输入、时滞多维非白噪声不平顺为输出的合成滤波器。建立车辆-桥梁垂向振动模型,并与合成滤波器联立得到一致白噪声激励下的车-桥-滤波器扩阶状态方程。继而提出求解此扩阶时变系统随机振动方差响应的递推算法。算例结果与MonteCarlo模拟法符合良好,表明该方法具有足够的精度,且对时间步长不敏感。     

Dynamic assessment of existing soft catenary systems using modal analysis to explore higher train velocities: a case study of a Norwegian contact line system

Significant advances made on the rolling stock have considerably increased the possibility of higher speeds in existing railways. Thus, it is important to explore higher speeds and potential limiting factors of existing soft catenary systems. The present paper investigates procedures to assess the dynamic behaviour of these systems using response sampling and modal analysis. The assessment evaluates and quantifies dynamic response along the section. To verify the approach, a case study is conducted and the following assessment methods are used: lengthwise track correlation estimating dynamic predictability, power spectral density estimations before and after passage and short-time Fourier transforms and spectrograms. The combination provides detailed information on the dynamic behaviour. The first part introduces necessary considerations for suggested modal analysis. The second part describes an existing Norwegian section. The case study is conducted using a finite element model including a straight and a given section between Oslo-Trondheim, providing detailed evaluations and system limitation detections.     

Estimation of wheel–rail friction for vehicle certification

In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. However, in associated test runs the wheel–rail friction condition is difficult to handle because the friction coefficient needs to be fairly high and the friction is also generally hard to assess. This is an issue that has been studied in the European project DynoTRAIN and part of the results is presented in this paper. More specifically, an algorithm for estimating the wheel–rail friction coefficient at vehicle certification tests is proposed. Owing to lack of some measurement results, the algorithm here is evaluated in a simulation environment which is also an important step towards practical implementation. A quality measure of the friction estimate is suggested in terms of estimated wheel–rail spin and total creep. It is concluded that, tentatively, the total creep should exceed 0.006 and the spin should be less than 1.0 m^?1 for the algorithm to give a good friction estimate. Sensitivity analysis is carried out to imitate measurement errors, but should be expanded in further work.     

单轨刚性接触网不均匀磨耗分析及对策

从接触网的角度,对单轨接触网在运行过程中受电弓滑板及接触线出现不均匀磨耗的原因进行分析,并提出相应对策,包括刚性接触网布置方法对磨耗的影响及改进、接触网安装精度对受电弓的影响.在车辆受电弓性能一定的情况下,通过对接触网的改进,减少不均匀磨耗的出现,改善弓网关系,延长受电弓滑板和接触线的使用寿命.     

The effect of railway local irregularities on ground vibration

The environmental effects of ground-borne vibrations generated due to localised railway defects is a growing concern in urban areas. Frequency domain modelling approaches are well suited for predicting vibration levels on standard railway lines due to track periodicity. However, when considering individual, non-periodic, localised defects (e.g. a rail joint), frequency domain modelling becomes challenging. Therefore in this study, a previously validated, time domain, three-dimensional ground vibration prediction model is modified to analyse such defects. A range of different local (discontinuous) rail and wheel irregularity are mathematically modelled, including: rail joints, switches, crossings and wheel flats. Each is investigated using a sensitivity analysis, where defect size and vehicle speed is varied. To quantify the effect on railroad ground-borne vibration levels, a variety of exposure–response relationships are analysed, including: peak particle velocity, maximum weighted time-averaged velocity and weighted decibel velocity. It is shown that local irregularities cause a significant increase in vibration in comparison to a smooth track, and that the vibrations can propagate to greater distances from the line. Furthermore, the results show that step-down joints generate the highest levels of vibration, whereas wheel flats generate much lower levels. It is also found that defect size influences vibration levels, and larger defects cause greater vibration. Lastly, it is shown that for different defect types, train speed effects are complex, and may cause either an increase or decrease in vibration levels.     

Locomotive dynamic performance under traction/braking conditions considering effect of gear transmissions

Traction or braking operations are usually applied to trains or locomotives for acceleration, speed adjustment, and stopping. During these operations, gear transmission equipment plays a very significant role in the delivery of traction or electrical braking power. Failures of the gear transmissions are likely to cause power loses and even threaten the operation safety of the train. Its dynamic performance is closely related to the normal operation and service safety of the entire train, especially under some emergency braking conditions. In this paper, a locomotive–track coupled vertical–longitudinal dynamics model is employed with considering the dynamic action from the gear transmissions. This dynamics model enables the detailed analysis and more practical simulation on the characteristics of power transmission path, namely motor–gear transmission–wheelset–longitudinal motion of locomotive, especially for traction or braking conditions. Multi-excitation sources, such as time-varying mesh stiffness and nonlinear wheel–rail contact excitations, are considered in this study. This dynamics model is then validated by comparing the simulated results with the experimental test results under braking conditions. The calculated results indicate that involvement of gear transmission could reveal the load reduction of the wheelset due to transmitted forces. Vibrations of the wheelset and the motor are dominated by variation of the gear dynamic mesh forces in the low speed range and by rail geometric irregularity in the higher speed range. Rail vertical geometric irregularity could also cause wheelset longitudinal vibrations, and do modulations to the gear dynamic mesh forces. Besides, the hauling weight has little effect on the locomotive vibrations and the dynamic mesh forces of the gear transmissions for both traction and braking conditions under the same running speed.     

Fatigue Analysis of Steel Catenary Risers Based on a Plasticity Model

The most critical issue in the steel catenary riser design is to evaluate the fatigue damage in the touchdown zone accurately. Appropriate modeling of the riser-soil resistance in the touchdown zone ca...     

‘Gasen-do FE’ statement of methods

Gasen-do FE is a simulation software for pantograph/catenary dynamic interaction analysis. Gasen-do FE is based on the non-linear finite element method, and its code is implemented in Matlab. This program corresponds to 2D and 3D models of simple and compound catenaries. Steady arms and catenary suspension equipments such as droppers and hangers are modelled as bar elements taking into consideration the tangential stiffness due to their geometrical non-linearity. It is possible to simulate the effect of slackening of droppers and hangers. This paper will introduce the computational algorithm of this program and the validation result by comparing with experimental data.     

CaPaSIM statement of methods

In the present paper, the method for calculation of the dynamic pantograph–catenary interaction developed by the Royal Institute of Technology and the Swedish National Rail/Road administration (Trafikverket) is described and the results of the benchmark exercise are discussed. The method is based on the commercial Finite Element software ANSYS. The geometry of the catenary and pantograph is defined in a pre-processor, BARTRAD, developed by Trafikverket, and is automatically translated into an ANSYS model. Basically all types of catenary systems could be handled as well as different types of non-linearity. There are both 2D and 3D versions of the code existing. The results achieved in this first stage of the benchmark are well in line with the results from the other partners in the benchmark study