Wheel-rail Forces Research Articles

Transverse Crack Propagation Characteristics of Rail Bottom under Wheel-Rail Force

The finite element model of multi-span continuous beam track is established to research the stress and strain fields of rail under the wheel-rail force. On this basis, according to the practical observation of crack shape, a three-dimensional semi-elliptical crack model was established, the singular element method was employed to simulate the stress field singularity of crack tip, and the transverse crack propagation characteristics of rail bottom under wheel-rail force was studied. The results show that: with the increase of wheel-rail force (vertical, lateral and longitudinal force), KI shows an increasing trend, and with the increase of lateral force, the increase rate of KI is maximum; with the increase of vertical force, both of the KII and KIII show a decreasing trend. However, with the increase of lateral and longitudinal force, both of them show an increasing trend. From the range of stress strength factor of crack tip, the amplitude of KI at the crack tip of rail outer edge is maximum , but the crack tip amplitude of KII and KIII is maximum at partial to the rail centerline.

HEMU 430-X 주행특성을 고려한 호남고속철도 곡선궤도구조의 거동연구

The wheel-rail interaction forces are influenced by the velocity of vehicle, wheel load, alignment (curve radius, cant etc). For the safety of track structure, it is required to evaluate the influences for track and influential factors. Recently, the HEMU 430-X, which was developed by Next Generation High-Speed Rail Development R&D Project, achieved 421.4km/h in a test run of Daegu-Busan section of the Gyeongbu high speed rail on March in 2013. In the case of additional speed-up test on Test-Bed Section(Gongju-Jeongeup: KP 100~128km Osong starting point), the analysis of track forces is required for outer rail by the increase of dynamic force and centrifugal force of vehicle. In this paper, the vehicle speed variation on HSL line is evaluated by TPS analysis considering the tractive effort of HEMU 430-X, tested running resistance and alignment of Honam HSR. And the track forces are evaluated by centrifugal force and impact factor on curved track.

Dynamic Properties of Double-Block Ballastless Track with Unequal Sleeper Spacings

Based on the vehicle-track coupling dynamics, by means of finite element method, the vehicle-double-block ballastless track-subgrade vertically coupled model is established to research the dynamic properties of double-block ballastless track with unequal sleeper spacings under the excitation of either long wave irregularity or short wave irregularity. The results indicate that the difference between the sleeper spacing and the standard sleeper spacing of the double-block track within the range of 70mm will not effectively affect the vehicle operation. The unequal sleeper spacing has a certain influence on the vertical displacement and acceleration of vehicle, rail and wheel rail force, but its influence on the force properties of track structure and vehicle operation stability can be ignored.

AN INVERSE DYNAMICS METHOD FOR RAILWAY VEHICLE SYSTEMS

The wheel–rail action will obviously be increased during the vehicles in high-speed operation state. However, in many practical cases, direct measurement of the wheel–rail contact forces cannot be performed with traditional procedures and transducers. An inverse mathematical dynamic model for the estimation of wheel–rail contact forces from measured accelerations was developed. The inverse model is a non-iteration recurrence method to identify the time history of input excitation based on the dynamic programming equation. Furthermore, the method overcomes the weakness of large fluctuations which exist in current inverse techniques. Based on the inverse dynamic model, a high-speed vehicle multibody model with twenty-seven Degree of Freedoms (DOFs) is established. With the measured responses as input, the inverse vehicle model can not only identify the responses in other parts of vehicle, but also identify the vertical and lateral wheel–rail forces respectively. Results from the inverse model were compared with experiment data. In a more complex operating condition, the inverse model was also compared with results from simulations calculated by SIMPACK.

Multi-point contact of the high-speed vehicle-turnout system dynamics

The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.

Influence of Track Support Stiffness of Ballasted Track on Dynamic Wheel-Rail Forces

Dynamic wheel-rail force can be limited to high-frequency components owing to imperfections in the wheel-rail contact surface (P1) and may also contain low-frequency components owing to coupled wheel-rail vibrations in phase on the ballast (P2). Previous studies on dynamic wheel-rail forces have focused on the quality index of surface roughness (QI) of only rail welds. In this study, the influences of rail surface roughness and track stiffness of a ballasted track on dynamic wheel-rail forces currently employed in high-speed lines were assessed by performing field measurements using actual vehicles running along the service lines. The theoretical dynamic wheel-rail force determined using a previous theory was compared with the dynamic wheel-rail force determined through field measurements. At a constant QI, an increase in the vertical track stiffness caused an increase in P2. Therefore, the vertical track stiffness affects P2 more strongly than P1. Hence, P1 is more affected by QI and train velocity than is P2. Further, it is inferred that the results of multiple regression analysis obtained using measured data such as QI, vertical track stiffness, and P2 can be used to predict the peak dynamic forces acting on ballasted tracks.

Study of Wheel-rail Force Decouple Based on Instrumented Rail

Eliminate the crosstalk of wheel-rail lateral force and vertical force is an important technology of high precision wheel-rail force measurement.An improved fast independent component analysis(Fast ICA) method is presented for wheel-rail force decoupling.This method judges remaining information and finds out the computation end point after one independent component is figured out though add a noise estimation threshold,and consequently,the improvement avoid useless compute and enhance the separating property and stability of this algorithm.Based on vehicle-track coupling dynamics theory,the dynamics model is established and the wheel-rail dynamic responses are calculated,and high precision wheel-rail force based on instrumented rail is obtained by means of improved Fast ICA decouple wheel-rail force.Finally,the algorithm is applied to field test,use genetic algorithm optimized metabolic GM(1,1) model to process discrete signals of rail force gained though field measurement to get the measure results of continuous wheel-rail force of each wheel,improved Fast ICA algorithm is employed to decouple it and acquire good effect.

Numerical Study of Impact Forces on Railway Sleepers under Wheel Flat

Wheel-rail interaction is one of the most important research topics in railway engineering. It includes track vibration, track impact response and safety of the track. Track structure failures caused by impact forces can lead to significant economic loss for track owners through damage to rails and to the sleepers beneath. The wheel-rail impact forces occur because of imperfections on the wheels or rails such as wheel flats, irregular wheel profile, rail corrugation and differences in the height of rails connected at a welded joint. The vehicle speed and static wheel load are important factors of the track design, because they are related to the impact forces under wheel-rail defects. In this paper, a 3-Dimensional finite element model for the study of wheel flat impact is developed by use of the FEA software package ANSYS. The effects of the wheel flat to impact force on sleepers with various speeds and static wheel loads under a critical wheel flat size are investigated. It has found that both wheel-rail impact force and impact force on sleeper induced by wheel flat are varying nonlinearly by increasing the vehicle speed; both impact forces are nonlinearly and monotonically increasing by increasing the static wheel load. The relationships between both of impact forces induced by wheel flat and vehicles speed or static load are important to the track engineers to improve the design and maintenance methods in railway industry.

Wheel-Set Hunting Movement and its Contribution to Coupling Vibration of Vehicle-Bridge System

Wheel-set hunting is an important and random lateral movement when wheel-set running on the track. Firstly a vehicle-bridge dynamic interaction model is established, in which the lateral wheel-rail interaction is defined by Kalker linear creep theory with the calculation of detailed wheel-rail contact adhesion geometric parameters and creep force. Then with the case of a high speed train passing a 32 m simply-supported beam bridge, the wheel-set hunting movement is calculated according to the relative vehicle and bridge lateral movement. And the characteristics of wheel-set hunting with different train speed and bridge stiffness are discussed. Then a simple lateral wheel-rail interaction is defined with close contact and no elastic deformation, and the contribution of hunting movement to coupling vibration of vehicle-bridge system is summarized in this method. The results show that the wheel-set hunting movement could be neglected when analyzing the bridge response, but it should be considered when analyzing the vehicle response in the vehicle-bridge interaction.

Coupling Dynamic Analysis of Floating Slab Track in the Urban Rail Transit

In order to study how the parameters of floating slab track and the speed of the train influence the vehicle-track coupling system，the paper built the vehicle-track coupling dynamic system. In the coupling model, the train is simplified a multi-rigid body system. The rail and the floating slab are considered as Euler beam. The wheel-rail relation is regarded as non-linear Hertz contact. The paper solved the dynamic equation of the vehicle-track coupling dynamic system with prediction-correction Newmark-β numerical integration method. Through numerical simulation, the paper gained the affect of fastener stiffness, slab support stiffness, and the speed of train to the characteristic of the coupling system containing the vehicle acceleration, wheel-rail force, the vibration of the track and the counter-force from the basis. The paper provides a reference for the selection of the track parameters and the speed of vehicle.

The Exploration and Research of CRTS I Slab Ballastless Track Used in the Freight Lines

The CRTSⅠslab ballastless track structure was the research object of this thesis and the truck vehicle-track dynamics coupled model had established in this thesis. Germany track interference spectrum was used as the track irregularity. The study analyzed the force conditions of the CRTSⅠslab ballastless track under the action of heavy freight trains in 110km/h, as well as the wheel-rail vertical force, vertical displacement and acceleration of the rail and rail board changes with time. The results show that the CRTSⅠslab ballastless track can meet the basic requirements of freight line.

Dynamic characteristics analysis of mats of ballasted track on bridge

A complete vehicle-ballasted track-bridge coupling dynamic model is established. A program to analyze dynamic characteristics is also invented, which is the first time to systematically analyze the dynamic characteristics of vehicles, tracks and bridges when using mats under ballast on the rigid foundation of bridge, in China. The results show that:(1) The mats under ballast are able to reduce vibration of the train and the wheel-rail forces by a certain extent, which increase the comforts of passengers.(2) The mats under ballast are able to reduce the stress of ballast, which has a great practical significance on avoiding ballast powdering and reducing maintenance work of ballast. (3) The mats under ballast are able to reduce the vibration of bridges. It has a great significance on avoiding the lateral flow deformation of ballast under dynamic loads, keeping good track geometry to ensure the safety of operation. DOI: http://dx.doi.org/10.11591/telkomnika.v10i7.1575 Full Text: PDF

Assessing the effects of track input on the response of insulated rail joints using field experiments

Manufacturers of insulated rail joints (IRJs) have to follow the quality assurance regime stipulated in the national design standards; unfortunately, IRJs still exhibit a very low and highly variable service life. It is widely believed that the service life of IRJs is affected by the track input under the passage of loaded wheels; however, there is a paucity of literature with regard to the actual mechanical behaviour of IRJs in the track. An extensive field test was, therefore, conducted on an in-service heavy haul corridor in Australia with the specific aim of understanding the effect of the track input on the response of the IRJs. Data on the wheel–rail force, rail/joint-bar strain, sleeper acceleration and ballast pressure signatures in the time domain were determined from the experiment. This data was subsequently systematically analysed to compare the relative structural merits of two IRJs resting on different sleeper spaces and a reference continuous rail subjected to similar real-life coal traffic loading.

Analysis of Experimental Data in the Context of Safety against Derailment of a Railway Vehicle, Using the Energy Method

This article describes an example analysis of safety against derailment of a railway vehicle. The analysis is based on the experimental data recorded during measurement of the wheel-rail interaction forces and lateral accelerations. The data is used for the calculation of two safety against derailment indicators and then the indicators are compared to each other. The first indicator is the ratio of the lateral to vertical wheel-rail forces Y/Q, based on the Nadal criteria. The second indicator is given in the energy description. In this description, the derailment of a railway vehicle depends on the amount of the work that has been done by the total lateral force acting on the single wheelset. The second indicator can be particularly convenient for a railway vehicle condition monitoring system, because it does not require the measurement of the contact forces.

Aerodynamic performances and vehicle dynamic response of high-speed trains passing each other

Based on the aerodynamics and vehicle dynamics, the aerodynamic performances and vehicle dynamic characteristics of two high-speed trains passing each other on the ground, embankment and bridge are studied. Firstly, a train aerodynamic model and a vehicle dynamic model are established. Through the simulation of the two models, the pressure waves, aerodynamic forces, and vehicle dynamic responses are obtained. Then, the pressure waves and aerodynamic forces on different foundations are compared. The results show that the variation trends of pressure wave and aerodynamic forces of trains passing each other on different foundations are almost similar. The peak-to-peak differences in pressure wave and aerodynamic force are below 4% and 3% in three cases in open air. Besides, the differences of security indexes, including coefficient of derailment, wheel unloading rate, the wheelset lateral force, and the wheel-rail vertical force, are below 2% among the three cases; the differences of comfort indexes, including the lateral acceleration and the vertical acceleration, are also below 2%. It is concluded that the dynamic performances of trains passing each other are influenced little by different foundations in open air.

플로팅 슬래브궤도와 일반 콘크리트궤도 접속구간에서의 열차 주행 안전, 승차감 및 궤도 사용성 평가

열차 진동 저감을 위한 플로팅 슬래브궤도의 설계에 있어서 주행 안전, 승차감 및 사용성을 확보하는 것이 매우 중요하다. 본 연구에서는 플로팅 슬래브궤도에서 열차 주행안전과 승차감, 사용성 확보를 위한 요구조건을 분석하여 제시하였고, 열차-궤도 상호작용을 고려한 동적 해석기법을 적용하여 시스템 고유진동수, 스프링 지지간격 및 배치방법, 감쇠비 등 주요 시스템 설계변수에 따라 일반 콘크리트궤도와의 접속구간을 포함한 플로팅 슬래브궤도 구간에서의 열차 및 궤도의 동적 거동을 분석하였다. 연구결과에 따르면 일반 궤도와 플로팅슬래브궤도 간의 접속구간에서의 지지강성의 차이에 의해 윤중 변동율, 레일 응력, 레일 인상력 등의 동적 응답이 크게 증가하는 것으로 나타났으며, 따라서 접속구간에서 스프링 지지간격을 좁히거나 스프링 강성의 차이를 완화시키는 방안이 주행안전과 궤도 사용성 확보를 위해 효과적인 것으로 나타났다. 한편 차체 가속도로 평가하는 승차감은 접속구간에서의 지지강성의 차이에 의해서는 거의 영향을 받지 않고, 시스템 튜닝 주파수에 의해 가장 큰 영향을 받는 것으로 나타났으며, 승차감 확보를 위해서는 적절한 시스템 튜닝 주파수를 선정하는 것이 매우 중요한 것으로 나타났다. 이 밖에 감쇠비, 스프링 간격, 열차속도에 따른 영향을 분석하였다. It is of great importance to assure the running safety, ride comfort and serviceability in designing the floating slab track for mitigation of train-induced vibration. In this paper, for this, analyzed are the system requirements for the running safety, ride comfort and serviceability, and then, the behavior of train and track at the floating slab track including the transition zone to the conventional concrete slab track according to several main design variables such as system natural frequency, arrangement of spring at transition, spacing of spring isolators, damping ratio and train speed, using the dynamic analysis technique considering the train-track interaction. The results of this study demonstrate that the discontinuity of the support stiffness at the transition results in a drastic increase of the dynamic response such as wheel-rail interaction force, rail bending stress and rail uplift force. Hence, it is efficient to decrease the spacing of springs or to increase the spring constants at the transition to obtain the running safety and serviceability. On the other hand, the vehicle body acceleration as a measure of ride comfort is little affected by the discontinuity of the stiffness at the transition, but by the system tuning frequency; thus, to obtain the ride comfort, it is of great significance to select the appropriate system tuning frequency. In addition, the effects of damping ratio, spacing of springs and train speed on the dynamic behavior of the system have been discussed.

Dynamic analysis of a coupled high-speed train and bridge system subjected to collision load

A dynamic analysis model is established for a coupled high-speed train and bridge system subjected to collision-load. A 7×32m simply-supported high-speed railway bridge with box girders is considered as an illustrating case study. A high-speed China-Star train is traveling on the bridge. The time history curve of a drifting-floe collision force is obtained from a field experiment and introduced as the excitation load on the bridge piers. Then, the dynamic response of the coupled train–bridge system subjected to the measured drifting-floe collision is calculated. Afterwards, the running safety indices such as derailment factor, offload factor and lateral wheel-rail force of train vehicles are investigated. The results show that the dynamic response of the bridge subjected to a collision load is much greater than the one without a collision, resulting in a big influence on the running safety of high-speed trains. For the case study, a critical train speed curve is proposed to evaluate the running safety of train vehicles on the bridge under drifting-floe collision with various intensities.

The Security Study of Train Derailment on High-Speed Railway Bridge

In this paper vehicle-bridge coupling system is divided into vehicle system and bridge system. The equations of vehicle vibration and bridge vibration are solved in numerical method, considered the displacement of wheel and rail as convergence criterion. The security of running train is studied on the hand of wheel-rail force, derailment coefficient, load decrement rate of wheel weight, and the reason of train derailing on high-speed railway bridge is analyzed. By the example of multiple span simple supported beam bridge, the result derived by this method is proved that the bridge meet train security and amenity requirement.

The Security Study of Train Derailment on High-Speed Railway Bridge

In this paper vehicle-bridge coupling system is divided into vehicle system and bridge system. The equations of vehicle vibration and bridge vibration are solved in numerical method, considered the displacement of wheel and rail as convergence criterion. The security of running train is studied on the hand of wheel-rail force, derailment coefficient, load decrement rate of wheel weight, and the reason of train derailing on high-speed railway bridge is analyzed. By the example of multiple span simple supported beam bridge, the result derived by this method is proved that the bridge meet train security and amenity requirement.

Wheel-Rail Multi-Point Contact Method for Railway Turnouts

A calculation method of wheel-rail multi-point contact based on the elastic contact model is introduced. Moreover, the simulation calculation of vehicles passing through branch lines of No.18 turnouts is carried out. The result showed that the acute change of wheel-rail normal force caused by the transfers of wheel-rail contact point between two rails can be avoid by wheel-rail multi-point contact method, and the transfers of wheel-rail normal force between two rails is smoother. The validity of wheel-rail multi-point contact method is verified.