Track Vibration Research Articles

Macro-meso dynamic analysis of railway transition zone: Hybrid DEM/FDM simulation and experimental validation

To probe into the mechanical behaviour of railway transition zone from the macro-meso aspects, a numerical model of transition zone is built that hybrids the Discrete Element Method (DEM) and Finite Difference Method (FDM). The DEM is utilised to simulate the ballast bed and sleeper, because it can consider the realistic ballast shapes and complex contacts between them. The FDM based on the continuum theory is utilised to simulate the track substructure according to a real structural form. Afterwards, the coupling algorithm is used to achieve the hybrid DEM-FDM simulation. The engineering practicality of this model is validated using the dynamic responses of the transition zone from a field measurement, and the macro-meso mechanical behaviour of the transition zone is analysed with or without the wedge-shape backfill. The numerical results indicate that applying the wedge-shape backfill can considerably reduce the sudden changes of track vibration and substructure surface stresses at the vicinity of the connection between the structure and embankment. Moreover, the mesoscopic results show that the acceleration vector of the soil near the rigid structure fluctuates towards the embankment and the velocity responses of track components and substructure increase gradually when the train travels from the rigid structure to the soft embankment.

Condition Monitoring of NFR Trains With Measurements From a Single Wayside 3D Vibration Sensor

The work reported in this paper aims at developing a simple one sensor based system to achieve condition monitoring of NFR (Northeast Frontier Railway, India) trains. Vibration of a railway track under train in motion provides important information about the train.To capture the vibration of a track under train in motion, vibration sensor ADXL335 is selected, as it is a reliable vibration sensor. Moreover ADXL335 shows insignificant effect of temperature on its measurements.Therefore it is considered to be suitable for measurement of vibration of a railway track under train in motion, because the temperature experienced by the sensor would vary during the train in motion as well as due to change in weather condition. To capture and store vibration data, an embedded system has been developed using Arduino Uno board. ADXL335 sensor is interfaced to the Arduino Uno board and software has been developed to capture 3D vibration of a railway track under train in motion. The captured data is transferred and stored in a laptop which is interfaced to the Arduino Uno board through USB port.The vibration data stored in the laptop is utilized to analyse the condition of the train using signal processing techniques. Time-domain and frequency-domain analysis of the vibration signals captured by ADXL335 installed in a railway track have been carried out to determine the condition of a train in motion. It has been observed that the time-domain analysis can provide information about slip and derailment tendency of a train, whereas frequency domain analysis can provide condition of different components of a train.

Experimental Study on Vibration Characteristics of Unit-Plate Ballastless Track Systems Laid on Long-Span Bridges Using Full-Scale Test Rigs.

In this work, we present a series of hammering tests on full-scale unit-plate ballastless tracks used for long-span bridges. There is no denying that it is a new attempt to pave ballastless tracks on high-speed railway long-span bridges; the related issues deserve to be studied, and especially the vibration characteristics. Hence, the vibration characteristics and transmission rules of the ballastless track with geotextile or rubber isolation layers are explored, and the vibration reduction effect of the rubber isolation layer is analyzed. The main conclusions are as follows: the isolation layers change vibration modes and transmission characteristics of ballastless tracks; the introduction of the rubber isolation layer makes the excited vibration frequency range of the ballastless track concentrated; and the vibrations of the ballastless track with the rubber isolation layers are stable. Moreover, the rubber isolation layer has an obvious attenuation effect on vibration transmission in ballastless track structures. When the vibration is transmitted from the rail to the bridge deck, the vibration level differences of the ballastless track with rubber isolation layers are 20 dB larger than that of the ballastless track with the geotextile isolation layers. The vibration attenuation rate of the rubber isolation layer is about ten times larger than that of geotextile isolation layer.

Train\u2013track coupled dynamics analysis: system spatial variation on geometry, physics and mechanics

This paper aims to clarify the influence of system spatial variability on train–track interaction from perspectives of stochastic analysis and statistics. Considering the spatial randomness of system properties in geometry, physics and mechanics, the primary work is therefore simulating the uncertainties realistically, representatively and efficiently. With regard to the track irregularity simulation, a model is newly developed to obtain random sample sets of track irregularities by transforming its power spectral density function into the equivalent track quality index for representation based on the discrete Parseval theorem, where the correlation between various types of track irregularities is accounted for. To statistically clarify the uncertainty of track properties in physics and mechanics in space, a model combining discrete element method and finite element method is developed to obtain the spatially varied track parametric characteristics, e.g. track stiffness and density, through which the highly expensive experiments in situ can be avoided. Finally a train–track stochastic analysis model is formulated by integrating the system uncertainties into the dynamics model. Numerical examples have validated the accuracy and efficiency of this model and illustrated the effects of system spatial variability on train–track vibrations comprehensively.

Data-Driven Bias Correction and Defect Diagnosis Model for In-Service Vehicle Acceleration Measurements.

Track quality instruments use low-cost accelerometers placed on or attached to the floors of operating trains, and these instruments collect substantial amounts of data over short inspection periods. The measurements collected by the instruments are the main data source for track irregularity evaluation. However, considerable measurement bias exists in the vertical and lateral vibration data obtained from such instruments. False positive track vibration defects detected by track quality instruments occur frequently. This results in considerable time and effort being expended needlessly because maintenance workers have to visit the railway track sites to check and review the track vibration defects. Therefore, we propose a model for data-driven bias correction and defect diagnosis for in-service vehicle acceleration measurements based on track degradation characteristics. Substantial amounts of historical track measurement data from different inspection methods were mined extensively to eliminate the false positive detection of track vibration defects and diagnose the causes of track vibration defects. Actual measurement data from the Lanxin Railway were used to validate our proposed model. The success rate achieved in identifying false positive track vibration defects was 84.1%, and that in track vibration defect diagnosis was 75.8%. These high success rates suggest that the proposed model can be of practical use in improving railway track maintenance management.

Coupled dynamic behaviour of a transmission system with gear eccentricities for a high-speed train

The transmission system of a motor car directly affects the operating reliability and running safety of a high-speed train. This study examines the coupled torsion vibration responses of a transmission system in a vehicle–track vibration environment. It considers the time-varying mesh stiffness, nonlinear damping characteristics, wheel flexible deformation and wheel–rail interactions. The results are compared to those of previous works as a means of validation. Then, the dynamic characteristics of the transmission system and its coupling effects are investigated along with gear eccentricity, which describes the torsional vibration properties in the vehicle–track coupled system more comprehensively. The results show that the traction torque and gear eccentricity affect the gear meshing, vibration amplitudes and frequency multiplication of the transmission system during the vehicle acceleration process. The eccentricity, especially of the pinion, has a great effect on vibration in the transmission system at high-speed ranges. Also, the dynamic responses of the wheels of the same motor car wheelset are different under traction conditions, which should not be neglected when assessing the torsional dynamic performance. The model provides a useful source of reference for the design and condition monitoring of traction systems for high-speed trains.

Experimental study of flying ballast at high speed railway applying track vibration

In this paper the complete approach is introduced for study of Ballast flying in wind tunnel considering track vibrations and aerodynamic loads. The air velocity profile under high speed train with speed of 300 km/h is introduced using an analytical approach and the intensity of under train wind is defined. About 50 kg of Iranian high speed railway ballast is adopted by random sampling and classified according to mass and aerodynamic shape. The critical velocities of ballast moving are measured by wind tunnel for all classification to obtain the ballast flying probability factor (BFPF) at two modes of with and without track vibration. Also, the conventional ballast flying risk mitigation methods in wind tunnel are reviewed and a new strategy for ballast flying risk mitigation is introduced and tested, based on the design of track surface by a special sieved group of ballasts with minimum flying probability factor. Results show that the BFPF increases in presence of vibration and the minimum value of BFPF is occurred at mass range of 150–200 g. It's stated that application of this group on the track surface may prevent from ballast flying due to passing of train with maximum speeds of 300 km/h.

Simulation of Power Generation from Vibration of Railway Track

Ethiopia has a small percentage of its population accessing electricity with some power utilized by its transportation sector; there are frequent power outages that slow down economic activities such as trade and railway transportation. From this previous statement, it is clear that the demand for energy is significantly increasing and there is too much dependability on the current energy source. With the development of sustainable energy technology in the world today, this problem can be alleviated, while utilizing component vibration in railway infrastructure. The aim of this study was to estimate energy generation potential from the vibration of a railway track induced by a passing train using a two degree of freedom oscillator. Data was collected; energy harvesting system was modeled and simulated. Based on the result, the system produces enough energy to power communication and signaling equipment on the track. The optimum parameters: mass of 1 kg, a spring stiffness of 6 N/m and a damping coefficient of 4 Ns/m of the energy harvester were determined using sensitivity analysis. The cumulative mechanical power harvested by the inter-city-125 train at a speed of 195 km/h was calculated to be 224.56 W. Therefore, the energy demand of the communication and signaling equipment of the train track can be achieved using vibration energy harvesting system by installing the number that meets the demand.

Towards an Energy-based Indicator of Track Quality in Turnouts

This paper investigates track vibration energy as a potential novel indicator of turnout’s track quality. Exploiting measurements of train-induced track vertical accelerations at different sections of a turnout, the track vibration energy is estimated and its variation over time analysed through the creation of statistical empirical distributions. A clear increase in vibration energy can be observed over a period of two years. An analysis of the turnout track geometry through a standard indicator adopted by the railway industry is then performed, and an increase in longitudinal level over the same investigation period clearly indicates track degradation due to cumulative loading. Last, a correlation analysis is performed between the estimated vibration energy and the indicator of track quality based on geometry data. Such analysis shows a significant correlation between the two indexes, thereby addressing the possibility of developing a novel condition monitoring tool for track quality based on track vibration energy. The whole investigation is based on full-scale measurements of track vertical acceleration and track geometry performed over a period of two years in a turnout of the Danish railway infrastructure.

Analysis of Vibration of Slab Track in TBM Tunnel According to Bottom Filling Materials

Due to the high speed of railway and the railway network passing through an urban area, the construction of tunnel using tunnel boring machine (TBM) has been increasing. During TBM tunneling, a deep filling section, about 3 m in depth, under the slab track is formed by the circular machine head. The research and the design standards for filling this section are currently insufficient. In addition, when the section is filled with lean concrete, it may negatively affect the propagation of train vibration. Therefore, it is necessary to analyze the dynamic behavior of filling materials and follow a suitable filling method. In this study, laboratory tests were conducted to determine the dynamic properties of bottom filling materials. Granular crushed stone with a cement content of 7-13% was selected as the filling material. Numerical analyses that reflect the results of the laboratory tests were also performed to analyze the dynamic behavior of the filling section under slab track. The results of these analyses showed that resonance occurred in the filling section depending on the critical and subcritical speeds of the vehicle. Keywords: TBM Tunnel, Bottom Filling Materials, Vibration of Slab Track, Resonance

The broadband seismic equipment application in problems of roadbed railway smart monitoring

We present our experience of broadband seismic equipment application to detect changes of roadbed railway state in operation.
 Aim: to obtain experimental validation to expand the scientific basis of geophysical surveys in roadbed railway state monitoring and identifying hazardous processes at an early stage.
 Methods: seismic records were obtained by the authors on the Northern railway section. Seismic data were processed using a low-frequency filter of 0.5 Hz and analysis of points movement trajectories of the roadbed railway, we performed numerical modelling of the stress-strain state of the soil when specifying various physical parameters, the results were compared with the experiment.
 Results: We have shown experimentally and by numerical simulation that by conducting near the railway track vibrations registration formed by passing trains and analyzing the amplitudes change of these vibrations in the low-frequency band (periods of about 100 seconds), it is possible to identify potentially dangerous phenomena in the roadbed. Field observations showed changes in amplitude of oscillations during seasonal flooding; the results are consistent with modeling. The possibility of identifying the stages of freezing-thawing of the soil and associated negative processes is considered. By discussing the parameters of modern seismic equipment, the possibilities and applicability of different types of seismic sensors for roadbed railway monitoring as well as the organization of a smart monitoring system are shown.
 Conclusion: The possibility of using passing trains vibrations to detect changes of the roadbed railway state by analyzing the amplitudes of these vibrations is proved. Recommendations for seismic sensors choice and organization of smart roadbed state monitoring system are presented.

Effect of Track Irregularities on the Response of Two-Way Railway Tracks

In predicting the response of track from a moving train only one track is generally considered. However, the effect of ground vibrations from one track and its effect on the nearby tracks has not been studied completely. Therefore, in the present paper, the effect of track irregularities and speed on the prediction of two-way tracks response is investigated. For this purpose, a three-dimensional dynamic finite element (FE) model capable of simulating interactions between the train and track by using a nonlinear hertz contact method was developed. The model uses tensionless stiffness between the wheel and rail to couple them. The model components including the sleeper, ballast, and soil domain are represented by solid brick elements. The rails are modeled as 3D Euler–Bernoulli beam elements. An iterative numerical algorithm was established for the integrations of the train and track interface. A comparative analysis was performed at various speeds and rail surface irregularity wavelengths. With the increase in speed, the results showed a significant increase in the adjacent tracks response and can induce much larger track vibrations at high frequency.

Track Occupation Detection Based on a Maximum Posterior Probability Model Using Multisensor Data Fusion

To address the railway track section occupation detection failure, this paper proposes a maximum posterior probability model that uses multisensor information fusion to detect track occupation. Based on the installation method of the sensor, this model obtains stable base data of occupied track sections and extracts its features, including train's running velocity, acceleration, direction, occupied area, wheelset axle counting, and track vibration. The maximum posterior probability and logarithm model are then derived by computing the prior probability, the posterior probability, and the conditional joint probability for the features. The judgment of the track occupation is more accurate compared with experience value. The experiments demonstrate that our track occupation detection method is able to effectively judge the occupation of the train, persons, and tool cart. Based on the maximum posterior probability, the Bayes optimal data fusion ratio for a measured parameter in this paper reaches 99.9983%.

Numerical Vibration Response of Railway Track Retrofitted with Single Degree of Freedom Rail Dampers

A concept and preliminary results of numerical study of changes in the rail track dynamic characteristics are presented in the paper. Change of the characteristics is introduced in order to reduce noise emissions. The theoretical relationship between the studied track dynamic characteristics (TDR - Track Decay Rate) and noise was briefly explained, and then the methodology of FEM modelling for the standard test simulation was described. Three mass modification variants and two rail types were analyzed. Damper connection were modeled as viscoelastic joint. The rail track vibrations were analyzed in both (vertical and lateral) directions separately. Numerical study shows correlation between the railroad track mass increase and its dynamic characteristics and thus the noise emission. Applying dampers with proposed parameters results in more efficient vibration and noise mitigation in lateral direction.

Two-way Hertzian spring in numerical analysis of coupled train-track system vibrations

The paper presents and compares two methods for simulation the train-track system vibrations, differing in the wheel-rail contact model used. In the first method, two-way Hertzian spring is used, in the second – a non-deformable constraint. In both methods, a flat computational model is assumed, consisting of an Euler-Bernoulli beam resting on a Winkler-type elastic foundation with damping and a set of rail vehicles modeled by dynamic systems with ten degrees of freedom. The results of numerical analysis are presented, in order to determine an influence of the contact constraints’ deformability on the vibration simulations. It is found that the replacement of non-deformable contact constraints by two-way Hertzian springs has no significant effect on track vibration simulations and has a little effect on vibration simulations of vehicle body and bogie. The developed simulation method can be used for numerical studies of the phenomenon of instantaneous detachments of wheels from rails, after minor modifications directed to introduce one-way Hertzian springs (i.e. not carrying tensile forces) being a more accurate contact model.

Transversal vibration analysis of the upper span of nonlinear closed-loop track systems

In order to analyze the effect of track pre-tension on the transversal vibration of the upper track, a multibody dynamics model of a tracked vehicle needs to be established. In view of the complex structure of tracked vehicles, the computational efficiency of conventional methods cannot meet engineering design requirements. In this paper, the Riccati Transfer Matrix Method for nonlinear closed-loop multibody systems is proposed and applied to the modeling and simulation of tracked vehicle systems. It avoids the overall dynamic equations of the system and achieves efficient computation with a smaller matrix scale. By selecting accelerations and forces as elements of the state vectors instead of coordinates and forces, linearization is avoided. The track chain is cut in a revolute joint. Its effect on the closed-loop system is represented by a set of constraint equations and internal constraint forces. An improved Riccati transformation for closed-loop systems is proposed to connect the internal force and acceleration parts in the state vector with the system constraint internal forces. The track pre-tension can be adjusted by moving the position of the idler relative to the chassis. The root mean square of vertical acceleration of mid-span with respect to the chassis is selected to evaluate the transversal vibration of the upper track. Simulation of a tracked vehicle driving on different road conditions is carried out with different idler displacements. Finally, a reasonable adjustment strategy for the track tensioner is proposed corresponding to different running conditions.

Characteristics of Vibration and Sound Radiation of Metro Resilient Wheel

Resilient wheels are extensively used in urban rail transit, especially for tramway systems, owing to its advantages in noise reduction. A new type of resilient wheel for a metro is designed, and its characteristics of vibration and sound radiation, including the rolling noise of a resilient single wheel coupled with a track, are studied in this paper. A two-step research is presented. Firstly, laboratory experiments were conducted to obtain the vibration response of the designed resilient wheel under the radial excitation on its tread. Secondly, the rolling noise model of the resilient wheel coupled with a slab track used in a metro line is developed. The wheel model is based on the 3D finite element and boundary element methods and verified by using the experimental results obtained from the laboratory. The track vibration model is based on the wavenumber finite element method, and the track sound radiation is calculated by using an efficient frequency-domain Rayleigh method. The interaction of the resilient wheel and the slab track is analyzed considering the measured wheel/rail roughness of the metro. The contribution of the resilient wheel to the reduction of wheel/rail system noise is analyzed. The results show that the resilient wheel can effectively reduce the wheel/rail rolling noise by approximately 2 dB(A) to 3 dB(A), mainly because the radiated noise by the rail is reduced. In addition, the elastic modulus of the rubber has an important influence on the noise reduction of resilient wheels.

Pendulum systems for harvesting vibration energy from railroad tracks and sleepers during the passage of a high-speed train: A feasibility evaluation

We evaluate the feasibility of recovering energy from the vibrations of track and sleepers, during passage of a high-speed train, by means of a pendulum harvester. A simple mathematical model of the parametric pendulum is employed to obtain numerical predictions, while measured data of vibration tests during the passage of a Thalys high-speed train are considered as input forcing. Since a sustained rotation is the most energetic motion of a pendulum, the possibility of achieving such state is evaluated, taking into account the influence of initial conditions, damping and other factors. Numerical simulations show that rotating pendulum harvesters with sufficiently low viscous damping could be able to generate a usable average power on the order of 5–6 W per unit. Considering a modular arrangement of devices, such energy is enough to feed variety of rail-side equipment, as wireless sensors or warning light systems. However, a suitable choice of initial conditions could be a difficult task, leading to the need of a control action.

Vehicle-track-soil interaction and train-induced ground vibration – Theory and measurements in Germany, Switzerland and France

Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.

A Comparative Study on the Beam and Continuum Finite Element Models for the Rail–Wheel Vibration

The rail–wheel interaction can induce train and track vibrations and consequently lead to noise impact, passengers’ discomfort, high maintenance cost, etc. Due to the complexity of the rail–wheel interaction and the high cost of field tests, as well as the difficulties in data collection, numerical analyses have been widely resorted to for predicting the train and track vibrations, for which numerous numerical models have been developed. According to track modeling approaches, numerical models can be generally divided into two categories, i.e. beam models and continuum finite element (FE) models. In this paper, these two models are systematically compared and discussed. First, a typical beam model of Wu and Thompson [T. X. Wu and D. Thompson, On the parametric excitation of the wheel/track system, J. Sound Vib. 278(4) (2004) 725–747.] is introduced, based on which a modified model is then established. Secondly, a plane continuum FE model with high mesh quality is established, in which the transition mesh generation, contact treatment and element size determination are presented. Numerical tests are conducted to validate the proposed plane FE model. Finally, both the beam and the plane continuum FE models are examined through typical rail–wheel interaction examples, in which the linear response of the track as well as the rail–wheel vibrations under both a single rolling wheel and two rolling wheels are analyzed. The results show that most of the vibration trends obtained from the two models agree well with each other. Nevertheless, it is noteworthy that the continuum FE model has superiorities, especially for analyzing vibrations at higher frequencies. The present study can be of considerable help for designers and engineers in the railway industry to achieve the trade-off between the simulation demands and the computational cost.