Correlation between rolling noise generation and rail roughness of tangent tracks and curves in time and frequency domains

Despite considerable advantages of the railway track over other means of transportation, noise pollution is the main adverse consequence of railway transportation. The basic cause of railway noise is rail corrugation. Although characteristics of railway noise have been considerably studied in the literature, rail corrugation effects on rolling noise generation in tangent tracks and the curves have not been sufficiently investigated. This research addresses the limitations of the current understanding of the rolling noise generation by investigating rail corrugation effects on rolling noise in tangent tracks and curves. This research was made based on the results obtained form a thorough field investigation carried out in a railway line which includes tangents tracks and sharp curves. A track geometry recording car was used to measure rail corrugations. For this purpose, an indirect method was developed in this research to obtain rail corrugation patterns from the data recorded by the track recording car. The effectiveness of the new method was shown. The induced noises were recorded using two particular types of microphones and implementing the method suggested by the ISO 3095 Standard. The rolling noise signal was distinguished from the total noise, using Butterworth Band-Pass Filtering. The role of rail corrugations in the rolling noise was discussed. Correlations were made between various types of corrugations and the induced noises. The results were presented and discussed in the spatial and frequency scales. Results obtained have led to new findings in rail corrugation effects on rolling noise generation. This research paves a way toward a better understanding of rolling noise sources and the parameters influencing the noise.     

Investigation of rail noise and bridge noise using a combined 3D dynamic model and 2.5D acoustic model

Bridge noise and rail noise are two major sources of an elevated rail transit bridge in the low and medium frequency range (20–1000 Hz). However, in most of the existing literature, the noise radiated from the bridge and rail was investigated separately or using a simplified source model. In this study, an accurate method is proposed to simulate both the rail noise and bridge noise simultaneously. First, the dynamic responses of the rail and multi-span bridge are obtained using a three-dimensional (3D) vehicle-track-bridge interaction analysis model. Then, the two-dimensional (2D) infinite element model is used to calculate 3D modal acoustic transfer vectors of the rail and bridge based on the wavenumber transformation, in order to overcome the singularity and non-uniqueness of the conventional boundary element method and reduce the computation cost. Third, a field test is conducted, and the accuracy of the proposed simulation procedure is verified. Finally, the contribution of the rail and bridge noise to the total noise level is investigated in the whole space near the bridge. Generally the bridge noise occupies a higher contribution in the space beneath the girder due to the shielding effect of the bridge shape on the rail noise, while the rail noise is dominant in the upper space above the bridge. It is found the presence of the vehicle bodies has considerable effect on the rail noise but little influence on the bridge noise. The slope of the roughness level spectrum has significant influence on the dominant field of bridge noise and rail noise. For the excitation of the assumed ISO roughness level used in this study, the difference between the rail noise and bridge noise is only about 3 dB at field points 15–30 m away from the track center, which indicates both the bridge and rail noise should be included in the noise prediction for an elevated rail transit bridge.     

On the dynamics of European two-axle railway freight wagons

The standardized design of European two-axle freight wagons has been used since the 1890s. The basic construction is a carbody suspended on leaf springs by a system of links working as pendulums. The internationally approved suspension system for these vehicles is the UIC standard suspension. The design is advantageous because it is simple, cheap, and robust. Despite the simple design, its influence on the dynamic performance of the vehicle is highly intricate due to dry friction damping and motion delimiters causing impacts. This paper deals with the dynamic behavior of European two-axle freight wagons analyzed through the use of a multibody model developed specifically for this purpose. The modeling of the vehicle and the integration of the dynamic equations of motion are far from trivial due to the complicated nature of the interacting forces. The model exhibits interesting bifurcation patterns emphasizing the complexity of the dynamic behavior of these wagons.     

钢轨缺陷的超声相控阵波数成像算法*

该文应用超声相控阵全矩阵捕获的波数成像算法,检测带有通孔缺陷的钢轨和B型相控阵试块。以实验获取的全矩阵数据为基础,研究了自发自收模式和全矩阵模式的波数成像算法,理论上分析了全聚焦方法和波数算法的计算性能,取得波数成像的结果并与全聚焦方法的成像结果做了对比。实验结果表明:波数成像算法具有更快的计算速度和更高的横向分辨率,且能够更加精准地还原钢轨中缺陷大小和形状,而传统的全聚焦方法计算耗时长,聚焦点分布不均匀,重建较大的缺陷出现了纵向拉长的现象,不能够较好地反映钢轨中的大缺陷。波数成像算法在各向同性材料实时检测中有很大的应用潜能。     

An Alternative Rail Pad Tester for Measuring Dynamic Properties of Rail Pads Under Large Preloads

One of the main components in ballasted railway track systems is the rail pad. It is installed between the rail and the sleeper to attenuate wheel/rail interaction loads, preventing the underlying railway sleepers from excessive stress waves. Generally, the dynamic design of tracks relies on the available data, which are mostly focused on the structural condition at a specific toe load. Recent findings show that track irregularities could significantly amplify the loads on railway tracks. This phenomenon gives rise to a concern that the rail pads may experience higher effective preloading than anticipated in the past. On this ground, this paper highlights the significance of accounting for effects of preloading on dynamic properties of polymeric rail pads. An innovative test rig for controlling preloads on rail pads has been devised. A non-destructive methodology for evaluating and monitoring the dynamic properties of the rail pads has been developed based on an instrumented hammer impact technique and an equivalent single degree-of-freedom system approximation. Based on the impact-excitation responses, some of the selected rail pads have been tested to determine such modal parameters as dynamic stiffness and damping constants in the laboratory. The influence of large preloads on dynamic properties of both new and worn rail pads is demonstrated in this paper. Additionally, the design criteria, which has been used to take into account the influence of the level of preload on dynamic properties of generic rail pads, are discussed. Note: The authors’ work in the references can be found electronically via UoW Research Online at URL     

The inverse identification problem and its technical application

This paper presents an overview of a loading force identification technique. Load identification methods are based on the solution of the inverse identification problem. Many different approaches for linear systems have been developed in this area. For both linear and nonlinear systems, methods based on the minimization of assumed objective functions are formulated. The least square error between the simulated and measured system responses is mainly used as the objective function. The dynamic programming optimization method formulated by Bellman is commonly used for the minimization of the objective function to estimate the excitation forces. The inverse identification problem in most practical cases is ill-posed because not all the state variables or initial conditions are known. Ill-posed inverse identification problems can be solved using several techniques, the most useful of which are: the generalized cross-validation method, the dynamic programming technique and Tikhonov’s method. This article presents the theoretical background and main limits to the application of inverse identification methods. Numerical and experimental tests on a laboratory rig were made to verify the formulated procedures. The method is applied to the identification of wheel–rail contact forces during rail vehicle operation. The method can be applied for indirect measurements of contact forces in railway equipment testing.     

Defect detection and location in switch rails by acoustic emission and Lamb wave analysis: A feasibility study

An acoustic emission (AE) based approach is proposed in this study to identify and locate newly initiated defects or the propagation of existing defects in railroad switch rails. Defect-induced AE signals are identified through frequency analysis, as frequencies of these signals are much higher than those induced by structural vibration. Continuous wavelet transform (CWT) is employed to analyze the Lamb wave dispersion of the detected signal, so that two characteristic points can be selected on the CWT contour map to locate the defect. Using this approach, defects in a damaged switch rail can be located using a single sensor.     

A factorial analysis for the determination of an optimal train speed with a desired ride comfort

A new method of optimization of the N_MV is proposed. The comfort index N_MV was measured and analyzed in research carried out for the Greek Railway network. Factorial analysis was used for the calculation of the effect of each factor on the comfort index N_MV. ISO 2631-1 standards were also involved in this study for the design of the equivalent vibration dose lines as a function of the N_MV and the exposure time. Using the factorial model, the N_MV index for different values of a train’s speed and rail condition was predicted. Finally, an optimum speed value, as regards acceptable passenger comfort, was obtained by using the equal vibration dose lines.     

A rail noise prediction model for the Tehran-Karaj commuter train

Rail noise prediction models enable consideration of different scenarios for the optimal management of noise prevention and mitigation. This project is aimed at developing an equation that enables computation of L_A,max for the Tehran-Karaj commuter train, a type of Diesel-Electric Locomotive. The form of the proposed model is derived from equations for predicting L_A,max for a single locomotive pass-by, proposed in the manual prepared by Harris Miller Miller & Hanson Inc. for the US Federal Transit Administration, and in the French rail noise prediction model. The algorithm for predicting L_A,max for the Tehran-Karaj commuter train has been developed on the basis of the 50 measurements from 5 locations at distances of 25 m, 35 m, 45 m, 55 m, and 65 m from the centre of the track and at a height of 1.5 m. In the field measurements, the reference distance and the reference vehicle speed have respectively been set equal to 25 m and 80 km per hour. The reference L_A,max, length and the speed correction coefficients have been estimated from the field measurements and have been found to be 86.2 dB(A), 11.3, and 18.4 respectively. The fitness test (Kolmogorov-Smirnov) and regression analysis indicate satisfactory results.     

Dynamic interaction between a moving vehicle and an infinite structure excited by irregularities – Fourier transforms solution

Summary  A new approach to calculate the dynamic interaction between a moving vehicle and an infinite structure is presented. Its main characteristics are: use of Fourier transformed domains (leading to a very general formulation of the problem), correct consideration of the motion of all components of the model; consideration of all kinds of mutual dynamic interactions between the vehicle and the track, and the possibility to include a layered half-space for the subgrade, instead of the elastic Winkler foundation used here. Examples of a single axle and a bogie model passing an irregular track illustrate characteristic effects. Received 13 December 1999; accepted for publication 21 September 2001 RID=" ID=" The research reported here was done at the Lehrstuhl für Baumechanik, (TUM). The authors are greatly indebted to Harry Grundmann for his interest and advice.