ICRT 2021

Modelling a whole vehicle-track-foundation-soil system is complex and usually the problem is split into several subdomains for predicting railway-induced ground vibrations. In this way, a modelling approach (multibody simulation, finite element analysis) dedicated to each subdomain can be adopted without any numerical constraint. A limitation however occurs regarding the interaction between each subsystem which is thus neglected. For some cases, the whole modelling does not allow an accurate simulation. A solution consists on co-simulation that can be applied to re-couple the decoupled model during the time integration process. The purpose of this paper is to analyse various techniques of co-simulation by considering theoretically a monolithic model, split at different location. A TCP/IP client/server binding is used for the data transfer during the numerical integration. An application case is then presented using two different software packages: EasyDyn, an in-house multibody simulation software, for the vehicle subsystem and ABAQUS, a commercial finite element software, for the soil subsystem.

Existing standards in Australia and many other countries determine track maintenance response and train speed restrictions mainly by judging the severity of isolated track defects. However, combined track defects (multiple types of track defects occurring in the same vicinity of a track section) pose greater challenges and risks for train operational safety. And there is a lack of quantifying research in terms of which combinations are the more severe and how maintenance schemes should be adjusted compared with responses to isolated track defects. This study proposed a method to identify severe track defect combinations that pose greater risks for vehicle derailments. A tabular tool was developed to help infrastructure managers to adjust maintenance reactions when track defects are found in combinations.

The cement asphalt (CA) mortar is an important part of the ballastless slab track system. The void between the slab and the mortar layer is prone to occur due to the particularity of CA mortar material and the complexity of external loads. To efficiently identify the mortar void, the local mean decomposition (LMD) is introduced to separate the wheelset acceleration into a set of production functions (PFs). The kurtosis of PF is calculated and PF1 containing the most damage information is selected for further processing. The instantaneous energy and the standardized instantaneous energy of PF1 are calculated. The result shows that when the length of the mortar void does not exceed 0.3 m, the method proposed in this paper cannot accurately locate the mortar damage. And when the mortar void length reaches 0.65 m, the standardized instantaneous energy has the best performance in the damage detection.

Active steering is an attractive technology to improve vehicle curving performance. It can reduce the track shift force and wear index in curves, but it is still unknown how much material removal across the wheel profile can be reduced and how it would affect the wheel wear evolution, which is crucial to motivate the implementation of active steering. This paper studies the wheel profile evolution under the presence of active steering. An iterative wear calculation approach is applied based on Archard’s wear model. Two practical steering control strategies are proposed. The wheel wear simulations are performed in three different scenarios, considering different rail cants and proportions of curves. The simulation results reveal the wear pattern of the actively steered vehicle and verify the reduced material removal across the wheel profile especially on the wheel flange. The two control strategies are also compared and evaluated for the future application of the active steering system.

As vital components of floating-slab track system (FSTS), the steel-springs vibration isolator and rail fasteners play a pivotal role to guarantee the safe operation of urban rail transit. Nevertheless, the existing damage detection methods are limited. This paper proposes an efficient method for compound damage (steel-spring and fastener) discrimination of the FSTS using 1D convolutional neural network (1D-CNN). In the method, a 1D-CNN is designed to automatically extract the damage-sensitive features from raw vibration response. The feasibility investigation of this method is tried on the acceleration of slab and rail respectively. And the vehicle-track coupled dynamics model is therefore employed to generate numeric dataset under different damage scenarios of steel-spring and fastener. Then the CNN is trained and evaluated on the acceleration datasets of slab and rail respectively. The result shows the method achieves a satisfied performance and it performs better on the dataset of slab acceleration than that of rail acceleration, which indicates such method has a great potential for the practical damage detection of FSTS.

A special methodology for the delivery of the change of friction coefficients has been developed. The results obtained with the proposed methodology are analyzed using the processing of raw data stored by the hand-operated tribometer. The analysis requires making some assumptions for the generation of input parameters for wheel-rail contact. One such assumption was achieved by the introduction of a function that allows to progressively increase friction coefficient for each successive wheel down the length of the locomotive. To understand locomotive behavior under this change of friction coefficients, the locomotive multibody model of a high adhesion locomotive has been developed in the Gensys multibody software. The results obtained show changes in the dynamic behavior of the locomotive and indicate the influence of this on locomotive dynamic performance. This study also shows that the further development of the proposed methodology might introduce some benefits for further advancement of wheel-rail damage theories for contaminated rails.

A series of simplified wheel-rail non-Hertzian contact models have been developed in the past two decades. However, the research on the application of these methods for vehicle dynamics simulation is still insufficient. This paper compares the computational results of different non-Hertzian contact models (NHMs) in vehicle dynamics simulation. Taking the computational results resulting from the Kalker's variational method (KVM) as reference, the computational accuracy of the Kik-Piotrowski (KP) model, the modified Kik-Piotrowski (MKP) model, the Ayasse-Chollet model, the ASD model, and the traditional Hertzian+FASTSIM model are evaluated. The simulation results indicate that the Hertzian model with a constant contact stiffness has better calculation accuracy than the original Hertzian theory and that the MKP+FaStrip model and MKP+FASTSIM model have an overall performance in vehicle dynamics simulations that is better than that of other simplified NHMs.

The bogie region has been identified as one of the important aerodynamic noise sources on a high-speed train. In this work, Computational Fluid Dynamics is used to simulate the flow around the bogie and the time-varying surface pressure is used as the input for the far field noise calculation which uses the Ffowcs Williams and Hawkings equation. The Delayed Detached Eddy Simulation method with Spalart-Allmaras turbulence model is used in the simulation of the unsteady flow field. In order to discretize the complex computational region of the bogie model, a hybrid mesh is used. The aerodynamic results show that the rear part of the bogie and its cavity have the strongest noise source intensity. The aeroacoustic results show that the cavity contributes more to the sound pressure level than the bogie does, and the sound energy is concentrated at the low frequencies.

This paper aims to build a rigid-flexible-liquid coupling rail vehicle dynamics model to study the lateral dynamics behaviour, which determines the vehicle hunting stability and running safety as well as ride quality. The liquid sloshing model is integrated into a simplified rail vehicle model concerning the nonlinear wheel/rail contact and deformable car body. The fluid element of the liquid sloshing model is a planar four-node rectangular element presented by the absolute node coordinate formulation (ANCF), which is employed to describe the large deformation of the free surface of the liquid inside container. The vehicle model accounts for the curving effects on the motion equations that influence the vehicle stability and curve negotiation. Verifications are performed to validate the fluid element efficiency, accuracy, and consistency, as well as the vehicle modes. Then the model is suitable for investigating the dynamic behavior of liquid carrier rail trains and its anti-sloshing.

Aiming at the problem of identification of physical parameters of railway vehicles, this paper proposes a method of on-site identification of physical parameters based on drop test. The physical parameter identification method is verified by simulation test. The recognition errors of different signal types are compared, and the results show that the physical parameter identification method has high recognition accuracy, and the acceleration signal and velocity signal have better recognition effect than displacement signal.

Pantograph-catenary dynamics determines operational speed, system reliability, and maintenance cost. The pantograph must negotiate the propagating waves excited by the pantograph itself. The dynamic performance is getting worse when the train is approaching the speed of wave propagation, which is called the critical speed. Normally, the permissible operational speed is below 70% of the critical speed. Very few studies or tests have studied the dynamic performance close to the critical speed. Because the Swedish catenaries were soft and haver relatively low critical speed, in the previous Gröna Tåget project, a series of tests were performed close to the critical speed of the tested catenary systems. Based on the measurement data and test feedback, this work studies the dynamic performance of the soft catenary system. The study gives insight into the critical speed range, which can be beneficial for the development of the pantograph-catenary system for the very high-speed operation.

To analyze the transient micro-vibration phenomenon of wheel-rail contact surface in multi-degree of freedom during service of high-speed train, regarding wheel of S1002CN tread and rail of CN60 as the research objects, combined with finite element multi-flexible body dynamics (MFBD) technology and train-track coupling dynamics theory, a high-speed train-track spatial coupling vibration model under wheel-rail flexible-flexible (F-flex) contact mechanism was constructed. High speed wheel-rail contact vibration characteristics under the condition of variable friction coefficient and empty train are analyzed. The results show that the change of wheel-rail contact status under different influence factors will affect the lateral and vertical vibration acceleration and frequency of flexible wheel-rail in different degrees. The fluctuation of the wheel-rail vertical vibration acceleration of loaded train is greater than that of empty train, and the excitation frequency of loaded train is more than that of empty train. According to the vibration acceleration and vibration displacement of the integrated flexible rail, it can be seen that the vibration amplitude and fluctuation of the flexible rail are more obvious than that of the empty vehicle in both vertical and lateral direction.

To ensure the ride quality of metro system in mountain cities, the characteristics of the wind-train-bridge system with high piers are studied, and the threshold of wind speeds and pier heights are determined in this paper. The representative crosswind model of Chinese hat fluctuating gust considering the speed-up effect of mountain terrain is established. The time series of this wind load is input to the dynamic system. The finite element method is used to model the bridge and the track, the multi-rigid-body system connected with the suspension spring and the damper is used to model each vehicle in the train. The whole process of the metro train running on the three-span high pier viaduct is simulated. On this basis, the analysis of the characteristics such as gust loading, different marshaling modes, wind speeds, and pier heights are taken into account. The study shows that the Chinese hat fluctuating gust model plays an essential role and resonates with the bridge structure in low frequencies, the crosswind stability of trains on high piers is more sensitive than short piers, the critical wind speed is 10.8 m/s and the critical pier height is 63 m.

A great number of long steep grades exist in the Chinese mountain railway. For example, Xi’an-Chengdu high-speed railway has more than 20 steep grades with gradients larger than 1.5%. The designed Sichuan-Tibet railway has a steep grade with a gradient of 3% and a length of 70km. Therefore, long-time and high-class electric braking will be applied when the high-speed trains pass through these severe grades, which may cause a higher braking failure risky. This paper presents a study of the effects of braking failure on the dynamic performance of high-speed railway vehicles when the train passes through these severe zones. Considering the train-track coupling interaction and the influence of track grade, a numerical model is established to study the effects of braking failure conditions on the dynamic performance of high-speed railway vehicles. The influence of the circular curve of the track is investigated as well. To better simulate the combined effects of braking failure, the model takes the coupler, the inter-vehicle components into account. The results show that the electric braking failure causes a significant increase of the train speed accompanied by intense in-train forces. The dynamic performance of the train under braking failure conditions is almost consistent with that under normal conditions.

Identification of the micro-mechanical parameters of the bonds in the polyurethane stabilized ballast still faces many difficulties at present as the identification of the parameters for other granular materials. Although the parameters can be repeatedly calibrated to macro-mechanical test results in the numerical modelling for various simulation purposes, it is time consuming and not always reliable. Aiming at this problem, this paper developed a simple laboratory test method using standard specimens to directly measure the micro-mechanical parameters of the polyurethane bonds under various loading conditions. The detailed test method and procedures are presented, and some preliminary test results for the polyurethane bonds are discussed. The measured values of the strength parameters via this method can be easily used for the discrete element modelling without parameter calibration work.

The dynamic analysis model of simply supported bridge under 2-DOF spring-damper-spring mass variable-speed moving load was established by using variable-speed moving load to simulate vehicle crossing bridge with variable-speed, and its motion government equation is deduced in detail. The dynamic responses of simply supported bridge under different stiffness degradation coefficients, different moving speeds, and variable speed moving loads were studied by numerical analysis. The results show that the stiffness degradation of simply supported bridge will affect the dynamic response of bridges and vehicles. With the increase in stiffness degradation, the acceleration amplitude of frame and vehicle body increases, and the dynamic performance of bridges deteriorates. Load of low-speed moving vehicles is more sensitive to the stiffness degradation of bridges, and the impact decreases relatively at high-speed; with the increase of load moving acceleration, the same stiffness will be obtained. Under the degradation coefficient, the peak acceleration of the frame and the carbody increases, and the peak acceleration of the frame increases more.

Industrial railways and small shunting yards rely on manually (remote-)controlled shunting locomotives or devices. The shunting process involves many idle times and manual work performed for the most part under dangerous conditions, thus making the shunting operation unattractive in view of increasing staff shortage and cost pressure. However, it also offers favorable boundary conditions for an automatization or even autonomization. This paper introduces an approach for automated shunting in order to overcome the drawbacks of conventional shunting operation and to improve its efficiency. A commercial shunting vehicle with automatic coupler was upgraded with sensors and further electronics to facilitate vehicle navigation and wireless communication. It receives shunting orders from a stationary control system and executes them automatically while monitoring the track. The feasibility of this approach was successfully demonstrated by field tests.

This paper proposes to use the principle of "Superharmonic Resonance" in theory of nonlinear vibration to explain a common frequency peak phenomenon in field tests of metro environmental vibration. Based on the theory of FMBD (Flexible Multi-Body Dynamics), a complex “vehicle-track-tunnel” model was constructed with help of Universal Mechanism software. Both flexibilities of railway track structures and nonlinear contact characteristics between the wheel and rail pairs have been taken into account, the Park method was used to solve stiff DAEs. Superharmonic resonance phenomena of wheel-rail forces and accelerations of substructure have been carried out numerically as expected. The principle can be not only used for analysis of environmental vibration, but also for study of out-of-round wheel as well as rail corrugation problems.

Rubber floating slab track (RFST) with good performance is taken as the research object in the paper. The vehicle-RFST coupling dynamic model and the acoustic (BE) model of RFST were established, then the numerical simulation method detailed studied the influence of vehicle suspension system parameters on the acoustic radiation characteristics of RFST structure. The results show that the main vibration frequency band of the RFST is 50–100 hz; the radiated sound field of the RFST is approximately symmetrical; the vertical stiffness of vehicle single stage suspension has a certain influence on the acoustic radiation characteristics of the track with the RFST; when vehicle suspension system parameter is taken into consideration, the theoretical research on vibration and sound characteristics of the vibration track would be more effective; the magnitude of 10⁶ is the best choice for the vertical stiffness of the single stage suspension of vehicles from the perspective of the acoustic radiation characteristics of RFST.

In order to study the vibration damping effect of small size vibration mitigation measures with PCs structure, the structural design and parameter analysis of period-structure rail pad are carried out based on Bragg scattering theory in this paper. The structure band gap is calculated by finite element method, and the influence of different design parameters on the band gap is analyzed to provide guidance for structure design. In order to compare the vibration reduction effect of the structure under the condition of finite period, a finite-period rail pad model was established to compare the DRT of ordinary and periodic pad. The results show that the band gap failure caused by rubber aging and rubber layer compression deformation can be solved by adjusting the elastic modulus of rubber to the stable rising stage of band gap and increasing the initial thickness of rubber layer. The vibration isolation performance can be brought into full play by adjusting the target frequency in the central region of the band gap.

Stiffness and damping are the key parameters that affect the dynamic characteristics of the elastic pad under the rail. In order to improve the damping of the elastic pad, damping blocks of different hardness are filled in the mesh cavities of the ordinary mesh type elastic plate. Research shows, the hardness of the damping block has a certain influence on the stiffness and damping of the mesh elastic plate filled with the damping block. Increasing the hardness of the damping block will increase the static stiffness of the entire plate of the mesh-type elastic plate filled with the damping block, while the damping ratio will decrease. The stiffness and damping of the mesh-type elastic pad filled with the damping block can be flexibly adjusted by changing the hardness of the damping block, making it suitable for track systems with multiple rigidity requirements.

The axle-box bearings are widely used in railway vehicles, which are of great importance for the running safety of trains. The service condition of railway vehicles has a significant influence on the reliability of axle-box bearings. The difference of the wear rate between the left and right wheels of a wheelset results in the wheel diameter difference (WDD). A freight wagon model considering the axle-box bearings is established and the effect of the WDD on the dynamic performance of the axle-box bearings is analyzed. The results show that the axle-box bearing on the side of the wheel with a larger radius has a larger contact force of roller-raceway. There is a phase difference between the load regions of the right and left axle-box bearings of a wheelset when the WDD exists. The differences of contact force and phase between the right and left bearings enlarge with the increase of WDD. The contact force is highly affected by the equivalent WDD of front and rear wheelsets in anti-phase and the WDD of the front wheelset. The number of rollers carrying the load is unchanged regardless of the WDD condition.

Coupler and draft gear system is an important component of vehicle used for connecting locomotives, motor cars or vehicles, which can transfer traction force, braking force, and mitigate longitudinal force. There are manufacturing and installation tolerances in the buffer, which lead to the fluctuation of mechanical properties of the buffer. In this paper, the mechanical model of HM-1 buffer, which can reflect the details of the buffer's internal structure, is established. By changing key structural geometric parameters in the model, we can simulate the buffer manufacturing and installation tolerance and study the effect of tolerance on the performance of buffer. By the means of studying on the effect of buffer manufacturing and installation tolerance on mechanical properties, the quantitative relationship between buffer structure and performance and the objective evaluation of buffer’s performance stability is obtained, which provides a useful reference for the effective control of buffer’s manufacturing and installation quality.

Rigid catenary is widely used as power supply device in tunnels, while the increase of speed poses new challenges to the stable operation of rigid catenary. Therefore, it is extremely necessary and important to study the performance of high-speed rigid catenary and pantograph system to ensure the safe and high-speed operation of electric locomotives. In this paper, dynamic model of rigid catenary is developed based on finite element method, considering overlap and interlocking joint structures. Lumped mass model of pantograph is taken to simulate the dynamic interaction of pantograph and rigid catenary system. The coupling model is verified by comparing simulation results with measurement data. The influence of key structural parameters and local structures on the dynamic performance of rigid catenary and pantograph system operating at high-speed is analyzed. The results show that the slight damage of structures has a greater negative effect on the current collection quality.

The vibration of railway carbody will eventually be transferred to passengers, which is generally measured by the vehicle ride quality index method. Therefore, the dynamic performance of the train is a representation of the vibration property of the train. The decrease of the modal vibration will affect the smoothness of the train. Modal parameters are the basic technical parameters of the dynamic performance of the car body, which reflects the overall property of the process, assembly, suspension components, and component inertia, and these can be identified by experimental design and testing. There is a certain relationship between the modal parameters and the running stability, but only the specific size can be obtained through the calculation of the ride quality index. A contribution analyze method of running stability was present by calculating the deformation of the car body under frequency response and the index of running stability. Comparing with the modal contribution, the modal with the highest contribution is taken as the main variable to improve the ride quality of the vehicle body for design or optimization. Results shows that at 120 km/h, the bounce vibration of the model is the main cause of the peak acceleration around 1.18 Hz, contributing to 91%. The contribution of modal is obtained to verify the calculation results of the contribution of running stability. The results show that the modal frequency and modal shape are the same in the sixth-order floating-rigid-body model. Then the bouncing vibration frequency was adjusted by optimizing the stiffness of secondary suspension system and the amplitude has been reduced by 44% at 1.18 Hz.

To meet the requirement of environmental vibration along the urban rail transit, vibration-attenuating track structures are widely used in special vibration-attenuating sections of metro railways. However, the vibration characteristics of different vibration-attenuating tracks are different due to the difference in supporting stiffness. In this study, a metro vehicle-track coupled dynamics model considering different types of vibration-attenuating tracks is applied to study the vibration characteristics of metro vehicles travelling on different vibration-attenuating track structures. The metro vehicle vibration characteristics and vibration transmission laws on different vibration-attenuating tracks are investigated through numerical simulations. The results show that the vibration characteristics are quite different for different vibration-attenuating track structures. The elastic-supporting-block track, the floating-slab track, and the ladder-type sleeper track have a good vertical vibration reduction effect in the frequency ranges of 0~10 Hz, 0~400 Hz, and 0~200 Hz, respectively. These track structures also have a good lateral vibration reduction effect in the frequency ranges of 40~70 Hz, 7~70 Hz, and 40~400 Hz, respectively.

To hill-start a 10,000-tonne heavy haul train on a mountainous railway, a triple locomotive unit is employed to provide traction power. Meanwhile, large dynamic braking forces are usually applied to control the train speed at the downhill section instead of air braking forces. The sustained dynamic braking forces influence the coupler stability, which further affects the running safety of the locomotives. To analyze the running safety of the locomotives under large dynamic braking forces, a multi-locomotive model is established and validated, and the dynamic performance of the locomotives on tangent track, curved track, and turnout under different dynamic braking forces are simulated. The results indicated that the large dynamic braking force leads to a large coupler yaw angle, which causes a large lateral component of coupler force and intensifies the wheel-rail interaction. To enhance the running safety of the locomotives, the applied dynamic braking force should be limited according to practical line conditions.

Research purposes: The finite element software and multi-body dynamics software are used to establish the analysis model of ground vibration caused by TR08 high-speed maglev vehicle. The maglev vehicle and viaduct are built in the rigid dynamics software. The three-dimensional hexahedron finite element is used in the soil calculation domain to calculate the domain boundary. The impedance and scattering properties are modeled by a three-dimensional viscoelastic dynamic artificial boundary. It is assumed that the TR08 high-speed maglev trains of one vehicle group are operated in straight line at different speeds, and the ground vibration characteristics generated by the numerical method are simulated and analyzed. Research conclusions: Compared with the existing research results, the calculation results of the method are basically consistent with the test results, and the ground vibration caused by the wheel-rail train is much larger than that of the maglev train under the condition of the same speed and other conditions.

Research on fatigue behavior of arch bridge suspenders is of great significance to the bridge design and maintenance. The dynamic stress responses of suspenders calculate by the static influence line method in the code, because track irregularities and the mutual vibration between the trains and the track-bridge are ignored, the dynamic stress cannot accurately reflect real stress response when the trains passes bridges. To more accurately calculate fatigue behavior of arch bridge suspenders, this paper presents an approach based on train-track-bridge dynamic interaction to calculate the dynamic stress time history of the suspenders. Fatigue stresses spectrum is obtained by the rain flow counting method, and used the S-N curve to calculate fatigue life of the suspenders. Taking a through tied arch bridge as an example, static influence line method and the proposed method are used to calculate fatigue damages of the short suspenders and the secondary short suspenders, respectively. The results show that fatigue damages of secondary short suspenders are more serious than the result of short suspenders under the action of train loads, which is the weak position of fatigue failure, it should be paid more attention during the operation of the arch bridge. The fatigue damage calculated by train-track-bridge method is larger than that by static influence line method. Although the result of the static influence line method ensures the fatigue safety of the suspenders in the design, it has a large error with the actual results.

Wheel polygon is one of the most common faults in railway industry threatening health of bogie components. Efforts have been made for years, to explore reason-solution and fault detection techniques for wheel ploygon. In China, 6A systems are widely applied for monitoring locomotive running safety. Among all 6A systems, an advanced truck defect diagnosis and record system (ATDR) focuses on fault detections of bogie components, including bearings, gears, and wheel trends based on analyses of sensor-collected bogie impacts. This paper tends to explore a wheel-polygon detection method based on sensor network of ATDR systems. A vehicle dynamic model was developed for a certain typical locomotive in China. Various typical wheel-polygon conditions were considered during simulations. Virtual sensors were placed on each axles and hugging-bearing box body (HBBB) for acquiring vehicle responses (acceleration) during simulations. Besides, impact features of axle-boxes and HBBBs were analysed via applying virtual demodulated resonance technique. Both time-domain and frequency-domain analyses were based between the normal conditions and wheel-polygon conditions. Simulations results were compared with field data. Finally, a wheel-polygon detection method was proposed.

In addition to very high wind speed with relatively short duration, there exist several key attributes of the winds associated with tornadoes such as the vortex-like structure with changing wind direction and probable existence of a “nose shape” wind profile at the tangential direction. Accordingly, the maximum wind velocity with complex spatiotemporal features generally occurs near the ground, potentially exposing the high-speed train (HST) to higher wind loads compared to classic atmosphere boundary-layer wind structure consideration. However, very limited full-scale tornado data and research are available to identify and reliably establish a description of the complex flow structure together and field with the resulting effects on the HST. In this study, the wind velocity field and pressure field in a typical tornado-like vortex, and their propagation to load effects on the HST are carried out using high-fidelity computational fluid dynamics (CFD).

Bearing is a basic component of the rotational mechanical system and its dynamic performance has a direct effect on the stability and reliability of the mechanical product, such as the railway locomotive. The wheel polygonization is a common wear of a locomotive in the running process. The more drastic vibration environment of the locomotive due to the intensified wheel-rail interaction will make the working condition of the motor bearing more complicated which is likely to cause bearing failures, such as pitting corrosion, spalling, plastic deformation, and cage fracture. In this paper, a locomotive-track coupled dynamics model with traction motor, axle box bearing, and gear transmissions is established where the bearing subsystem supporting the motor rotor and the pinion gear is considered in detailed so that the skidding characteristics, the nonlinear contact forces between the components of the bearing and the corresponding friction forces are included. The results indicate that the intense wheel-rail interaction caused by the high-order wheel polygonization will affect the dynamic characteristics of the motor bearing significantly. Furthermore, this model can assess the skidding phenomenon of the motor bearing under vehicle vibration of a locomotive effectively.

The design idea of express wagon is to ensure that the car-body has the characteristics of hi-cube capacity and easy loading and unloading which indirect causes the stiffness of car-body is changed with uncertain factors, such as the full sliding side covered and other forms of design, thus the running stability of the vehicle operation is affected and the risk of the transported goods is damaged will be increased. The random dynamic analysis for the express wagon is operated with the railway vehicles random analysis procedure (RVRAP) according to the analysis process firstly, then the uncertain stiffness is described by random variable and the modified stochastic perturbation method is employed to establish a deterministic approach. In this paper, the random variable parameter of side post stiffness for the express wagon is selected and the running stability index at three positions on the underframe are calculated. The result shows that the parameter uncertainty of stiffness of the side post has a greater impact on the vertical running stability than the lateral and ignoring the uncertainty of the parameter will result in a higher stability evaluation result.

With the increase of train speed, the influence of vehicle vibration and noise on ride comfort is increasingly significant. Using active control elements to control vehicle vibration has become one of the main research directions. In this paper, the magnetic levitation electromagnetic actuator based on the linear quadratic regulator is given. Firstly, the validity of the control theory is verified by simulation and experiment, and then the control theory is applied to the railway vehicle model for simulation analysis, and the time-delay effect is researched. The simulation results show that, when the time-delay effect is not significant, the actuator has obvious promotion in resonance region, and it has certain effect on optimizing the Sperling index.

This paper takes the universal segmented tunnel structures in the Shanghai Metro lines as the research object. A three-dimensional shell-spring-contact model is established to consider both the longitudinal and lateral characteristics of the universal segmented tunnel structures. The mechanical properties of the universal segmented tunnel under different geological conditions are analyzed. The results show that the transverse deformation of the tunnel is larger than the vertical deformation for all the considered conditions. As the typical geological conditions change from clay to sand, the maximum transverse and vertical deformation of the tunnel decrease, as well as the principal compressive stress and the damage area of the tunnel segment.

The brake cylinder charging time is an important parameter in the air brake system and it affects train performance such as braking distance, coupler force, and car acceleration. For the discrepancy of brake cylinder charging time between the rapid freight car and the general-purpose freight car, the longitudinal impulse in the mixed formation train is more complicated. This paper proposed a mixed formation train model with the rapid freight car air brake system and the general-purpose freight car air brake system. The influence of the brake cylinder charging time difference on coupler force of mixed train was predicted. The results show that due to the difference of brake cylinder charging time, the marshaling position of rapid freight cars affects the coupler forc, and the rapid freight car located in the rear of the train is preferable. The longitudinal impulse of the mixed train with rapid freight cars located in the rear decreases with rapid freight car brake cylinder charging time reduction.

Based on the theory of vehicle-track coupled dynamics and the actual parameters of the 27 t axle load side-frame cross-braced bogie, the heavy haul railway vehicle-track dynamic model on curved track was established, and by utilizing the computer simulation method, the influence of some curve geometric parameters such as curve radius, rail superelevation, et al., on dynamic interactions were simulated and analyzed. It is found that the curve radius has obvious effects on dynamic interactions, especially at the range of 800 m; lengthening the transition curve can decrease the dynamic forces to some extent, but there is an inflexion, before that, the variation of the length of transition curve affects obviously, after that, does little; much too deficient or surplus superelevation will both aggravate the wheel/rail dynamic response; and almost every dynamic indicator has no changes with the length variation of circular curve. The results indicate that the curve radius is the key parameter affecting the dynamic interactions, the minimum curve radius should be more than 800 m; the influence of length of transition curve on dynamic interaction has an inflexion, normally the minimum length of transition curve can be determined by the inflexion (40~60 m); it is beneficial to negotiate a curve with the equilibrating superelevation or the proper deficient superelevation (≤ 20 mm); and the length of circular curve has almost no effects on dynamic interactions, its length can be determined by the actual engineering needs.

With the rapid development of urbanization in China and the continuous improvement of people's living standards, urban traffic congestion and people's travel efficiency have become urgent problems to be solved. Urban rail transit has many advantages, such as high capacity and efficiency, low energy consumption, fast and convenient, safety and comfort, etc., which has become the most effective measure to solve the above problems, and also an important way to realize the adjustment of urban spatial layout and balanced urban development. The main characteristic of urban rail transit development in China is that it starts late but develops rapidly. At present, urban rail transit lines had been built in many cities, among which the urban rail transit network in major cities has basically realized the whole coverage of urban areas. According to the construction mode, urban rail transit can be divided into three types which are underground line, ground line, and elevated line. The environmental vibration problem caused by underground line operation has been highly attention. The ground buildings’ vibration in sensitive areas such as hospitals, museums, heritage buildings, scientific research institutes, and libraries is a hot research topic, but the vibration and noise in vehicle are often ignored. The noise on the ground line and the elevated line will have a great impact on the lives of the residents along the line. Together with the environmental vibration, both impacts will affect the lives of the surrounding residents. At present, the research on urban rail transit mainly focuses on the design and development of track damping and its related performance that the aim is reducing the environmental vibration. In addition, the research of bridge acoustic-vibration characteristics on elevated lines is often studied. However, when a train passes the elevated bridge that lay the track, the track will become the sound source by its vibration and the noise can be radiated as well. Combined with the acoustic radiation of the bridge, the whole acoustic radiation of the elevated line will be aggravated. At present, there are few research of the acoustic-vibration characteristics of the track structure on the bridge. Therefore, the steel-spring-floating-slab-track (SSFST) with good performance of vibration damping in China is taken as research object in the paper. The vehicle-SSFST-box girder bridge coupling dynamic model and the acoustic boundary element model of SSFST are established and adopt the numerical simulation method to detailed study the acoustic-vibration characteristics of SSFST on the bridge. The research results can provide theoretical foundation for the noise reduction design of SSFST.

With the increase of railway mileage, the problems of subgrade settlement and upper arch have gradually become the main problems of railway foundation disease control. Traditional disease control methods are mainly a series of complex, large amount of engineering and high cost of mechanical lifting, and grouting control measures. Our team proposed a short-sleeper ballastless track structure with adjustable height, aiming to use this new track structure to transform the subgrade settlement over 100 mm from subgrade regulation to track regulation. The study shows that the structure can effectively adjust the settlement of the subgrade and the upper arch under the track with the height of 100 mm through geometric matching relationship. The first order of mode mode before and after the sleeper is raised is vertical downward, that is, the structure can maintain the overall structure stability after the lifting, which is matched with the traditional track structure raising ability.

The levitation force between the magnetic field captured by the high temperature superconductor (HTS) and the magnetic field of permanent magnet rail is important for the high temperature superconductor magnetic levitation vehicle, which can guarantee the self-stabilizing suspension and directly determine the capacity of the vehicle. In this paper, the finite element method is used to analyze the levitation force. The captured magnetic field of HTS is obtained by way of calculating the magnetic field at the field cold height. The levitation force between HTS bulk and permanent magnet is calculated by the captured magnetic field and low magnetic permeability, which is validated by way of experiment. Based on above method, the levitation force between multiple HTS bulks installed on magnetic levitation vehicle and the permanent magnet rail is calculated. By designing the sandwich structure consisted of multiple HTS bulks and permanent magnet rail, the levitation force of high temperature superconductor magnetic vehicle can be effectively increased, which provides the basis of force characteristics for the dynamic modeling and simulation analysis.

This paper focuses on the research of stress analysis of rail vehicle axle with considering the effect of an interference fit, through the traditional contact stress formula based on the mechanics of elasticity and the finite element method, to analyze the relationship feature of axle surface stress and interference fit value. First, draw out graphs according to the stress data of eleven selected axle sections and corresponding interference fit value. Then, calculate the linear correlation coefficient by numerical analysis method to prove the linear relationship between interference fit value and the calculation stress of axle. Finally, using the least-square method to find out the best approaching straight line of each axle section. Following the linear relationship, with limited data, it can estimate axle stress with different values of interference fit.

In order to explore the relationship between the bending frequency of flexible car body and the suspension parameters, this paper use the finite element method to analyze the frequency of car body, and then the formula which calculated the pith and bounce frequency of bogie is derived by simplifying the vertical dynamics model. Therefore, the formula of the ratio between the first-order bending frequency of car body and the pitch and bounce of bogie was established. Finally, the rigid-flexible coupling dynamics model was established. Through simulation analysis, it was found that the vertical amplitude of car body will increase and ride index will reduce while the first-order bending frequency of car body which reduced within a certain range is close to the vertical vibration frequency of the bogie, but the standard for vehicle dynamics performance requirements can still be met by selecting the appropriate suspension damping ratio. Although the vibration amplitude of the bogie may increase in a small range while a suspension damping ratio was selected, the vertical ride index of the vehicle will be significantly improved. The research results show that the frequency of the lightweight car body could no more than 10 Hz and no more than 1.4 times the pitch and bounce frequency of bogie while the suspension parameters was selected suitable.

For the locomotive with axle suspension, the driven gear is pressed-fit and integrated with the wheel into a whole. The helix angle can improve step characteristics of meshing stiffness for the gear transmission system which dynamic performance has a direct effect on the locomotive and its components. This paper proposes a gear-axle suspension locomotive coupled system dynamic 3D model, the gear transmission is coupled with a traditional locomotive dynamics system via the gear mesh interface. The influence of helix angle in the range of 0°~20° on dynamic behavior of locomotive traction gear transmission system is investigated in detail, the peak acceleration trend indicated that the helix angle of 8° minimizes vibration acceleration in three directions. The vibration acceleration peak value on the vertical, lateral, and rotational direction with the helix angle of 8° is compared with the helix angle of 0°, the three values decreased approximately 29.8%, 29.8%, and 29.6%, and the amplitude-frequency characteristic indicated that high frequency harmonic components of gear transmission system can be obviously improved by the helix angle. The results verify that helix angle have effect on the lateral dynamic responses of wheel in the coupled system.

Taking subway vehicles as an example, this paper compares the influence of track irregularity on the dynamic response of vehicles on a straight line, and studies the changes of vertical wheel-rail force, lateral wheel-rail force, derailment coefficient, wheel weight loss rate, and other dynamic responses of vehicles when the train is running on a plane curve. The research results show that, when the definite track irregularity exists on the curved line, the impact on the vehicle dynamic response is more significant than that on the straight line. Therefore, it is suggested that when analyzing the vehicle dynamics response, the analysis of the vehicle dynamics response under the curve model should be emphasized. As the radius of the curve or the operating speed increases, the safety of subway vehicles becomes worse. Therefore, when the subway is running, the speed through the curve must match the curve radius. The welding seam irregularities at different curve positions have different effects on the vehicle dynamic response. The influence on the straight and gentle points is the largest, the influence on the circular curve section is in the middle, and the influence on the gentle points is the smallest.

A modified nonlinear fatigue damage accumulation model was presented for prediction of the rail head check (HC) initiation in the rail by considering the influence of the load sequence and adjacent loads interaction. Results show that the fatigue damage by the nonlinear model was faster and the HC initiation life was shorter than those from the linear model. Moreover, the HC initiation life from the linear and nonlinear models was close to the upper range value and median of the field observation respectively.

In view of the phenomenon of car body lateral alarm after the grinding of high-speed railway turnout, the different grinding methods of the turnout are researched. The wheel-rail contact model and the dynamic model are established while the high-speed train passing the turnout by the vehicle dynamics software. After that, the wheel/rail contact geometry characteristics, the wheel-rail wear, the vehicle running safety and the vehicle running stability are calculated, and the actual running stability of high-speed train vehicles after different grinding methods are compared. The results show that, compared with the traditional turnout rail grinding method, the left and right side of the turnout rail are symmetrical, and the wheel-rail equivalent conicity is more ideal after personalized turnout rail grinding. Moreover, when the train passes through the turnout, the wheel-rail wear, the operation safety, and the lateral stability are significantly improved, which is consistent with the measured data from field tests. Thus, the personalized grinding method can avoid the phenomenon of car body lateral alarm after the grinding.

The static stiffness of some arm positioning rubber nodes from 3 manufacturers. These arm nodes reaching the advanced maintain stage have been in served 1,200,000 km in Beijing-Shanghai, Wuhan-Guangzhou high-speed railway lines. The stiffness variation range of arm node for different manufacturers and lines is analyzed. The dynamics simulation model of CRH₃ trailer is established in the Simpack software, and the validity of the model is verified with the acceleration test data of the carbody. The influence of the stiffness on the dynamic performance of vehicle is calculated and analyzed for the 60N, 60D rail profile. The results show that after serving 1,200,000 km, the radial stiffness distribution is between 85.1 ~ 158.5 MN∙m^-1, and the stiffness change rate is within the range of -38.9%~18.6%. The stiffness variation range is similar between Beijing-Shanghai and Beijing-Guangzhou high-speed line, but it is quite different for various manufacturers. With the increase of longitudinal stiffness of the arm node, the nonlinear critical speed gradually decreases, and the sperling index, lateral force of wheelset, wear index gradually increases, but all of them are less than the safety limit. These dynamic performance indexes of 60D rail are greater than 60N rail. When the longitudinal stiffness is greater than 140 MN∙m^-1, the CRH₃ matching the 60D rail is more sensitive to the variation of wheel-rail profile and prone to the vibration problem of abnormal low equivalent conicity. To improve the adaptability of wheel-rail matching, it is suggested to appropriately reduce the nominal longitudinal stiffness of the arm node for CRH₃ EMU.

In order to investigate the causes and development characteristics of rail corrugation in small radius curve, the wheel-rail contact and creep characteristics and the dynamic responses of wheel-rail system on the common fastener track were analyzed by using the metro vehicle-track dynamic model. The inside wheel-rail creep force appears periodic unsaturated-saturated zonation phenomenon, which makes the wheel-rail interface in the stick-slip state all the time, resulting in rail corrugation eventually. The outside wheel-rail creep force is always saturated, which illustrates that the wear is relatively serious, but it is not easy to form wavy wear with the periodic characteristic. The fluctuation amplitude of wheel-rail vertical/lateral force on the inner rail side is larger than that on the outer rail side, which easily leads to the further development of inner rail corrugation. The characteristic wavelength of the axle box vertical vibration acceleration on the inner rail side appears at 32 mm, closing to the measured wavelength of the inner rail corrugation, which indicates that the wheel-rail system has an unstable vibration at the frequency corresponding to that wavelength, leading to the aggravation of the vibration of system components.

As a wheel travels along the rail, the wheel-rail force moves along the wheel’s periphery at the train speed, generating wheel vibration which is complicated by the moving load effect along with the gyroscopic and centrifugal effects caused by rotation. To accurately predict sound radiation of a wheel in rotation, all the rotation effects mentioned above should be considered. In this paper, the Fourier finite and boundary element methods are employed to predict vibration and sound radiation of 9 high-speed train wheels of the same design but with different damping treatments (including a bare wheel without any damping treatment as reference. In total there are 10 wheels for study). Comparison is made for the 10 wheels in the overall A-weighted sound power levels between two conditions, i.e., whether or not rotation is considered. The damped wheel which produces lowest noise can be determined. Finally, three damped wheels are chosen for further analysis, aiming to work out the contributions of energy dissipation and receptance change to the achieved noise reduction.

In order to explore the acoustic radiation characteristics of single-track and double-track box girder bridges, firstly, two kinds of finite element models of train-track-bridge are established; secondly, the acoustic radiation characteristics of two kinds of box girder bridges are analyzed by using the acoustic boundary element method (BEM); finally, the acoustic radiation characteristics of two kinds of box girder bridges are compared. The results showed that: the vibration acceleration response of single-track box girder bridge was larger than that of double-track box girder bridge, and the dynamic responses in frequency domain of the two kinds of box girder bridges were relatively dense in the range of 0~100 Hz; at each horizontal field point equidistant from the bottom plate of box girder, the attenuation speed of sound pressure level of single-track box girder bridge was slightly smaller than that of double-track box girder bridge; the sound pressure level of radiated noise of single-track box girder bridge was larger about 0~12 dB (L) than that of double-track box girder bridge at field point directly above the top plate of box girder.

The vibration problem caused by high-speed railway trains passing at high speed has been paid much attention at home and abroad. Based on the theory of train-rail-bridge interaction and power flow method, this paper studied the internal energy transfer characteristics of elevated lines, and further analyzed the vibration isolation performance of the components on elevated line systems. The research showed that the fastener system and CA mortar layer can absorb and dissipate the vibration energy of elevated lines, which are the key parts to be considered in the later research on high-speed railway vibration reduction.

This paper mainly studies the networked stochastic system stability and H_∞ control when the multi-particle model of high-speed train (HST) is transformed into the Takagi-Sugeno (T-S) fuzzy model. Firstly, the sampling control system with two sampling frequency is set up, dealing with the sampling control system with input time delay method, turning it into continuous system with time-varying delay, introducing a meet the Bernoulli distribution of random variables, by aid of these methods establish model. Secondly, the design method of state feedback controller for networked stochastic system of high-speed train is given, and the closed-loop system of this model is obtained. Finally, the stability of the system is analyzed by the proper Lyapunov-Krasovskii functional (LKF) of the component, and the sufficient condition of the mean square asymptotically stable of the closed-loop system under the constraint of performance index H_∞ is obtained by further considering the norm bounded uncertainty in the system.

In this paper, acoustic FEM, acoustic BEM, and acoustic phenomenon model of porous materials are combined to analyze the influence of the geometry parameters and absorptive character of low-height sound barrier on its acoustic insertion loss. For the standard field points, the closer the sound barrier is to the rail, the higher the sound barrier, lead to the greater acoustic insertion loss of the sound barrier. Compared with the higher sound barrier, low-height trackside sound barrier has less insertion loss at the lower near-field point. For higher near-field points, compared with higher sound barriers, the non-absorbing trackside sound barriers can achieve equivalent acoustic insertion loss. For the far-field point, the insertion loss of the trackside sound barrier is equivalent to that of the higher sound barrier. The absorptive structure can improve the acoustic insertion loss, but the enhancement of the insertion loss of the high sound barrier is greater than that of the low-height trackside sound barrier.

The large-scale operation and maintenance equipment of railway lines is developing towards hybrid power and full-electric driving. The special electro-hydrostatic actuator is developed based on the hybrid transmission idea of power by wire and power by hydraulics. The micro-pump and flow matching valve of key components were developed based on the special electro-hydrostatic actuator for large-scale operation and maintenance equipment of the railway line, and the virtual prototype modeling and simulation were carried out to verify the stability of the special electro-hydrostatic actuator system and the effectiveness of the key technologies. The prototype of electro-hydrostatic actuator was trial-manufactured and a four-quadrant working condition simulation test platform was developed. The functional integrity and theoretical correctness of the special electro-hydrostatic actuator were verified through the prototype test. It lays a foundation for the subsequent control of electro-hydrostatic actuators in the application scenarios of large-scale railway line operation and maintenance equipment, and provides a reliable scheme for the upgrading and development of large-scale railway line operation and maintenance equipment.

Diesel locomotives produce harmful gases during the traction process. If the ventilation equipment in the tunnel cannot discharge harmful gases in time, it will cause subsequent trains entering the tunnel to stop and wait at the station ahead, which will eventually affect the carrying capacity. Therefore, we study the calculation method of railway capacity based on the current single-track automatic inter-station block (semi-automatic block). With taking into account factors such as the minimum ventilation time determined by the tunnel ventilation equipment, a method of combining diagrams and calculations was proposed to obtain the capacity of the "restricted block section" or "restricted district". We take Luoding-Cenxi railway's south line scheme and north line scheme as an example testify validity of the method. The similar method described above can also be applied to double-track internal combustion railways. Moreover, it can provide an auxiliary decision-making basis in the process of railway survey and design.

Urban rail transit can increase property prices by increasing higher accessibility and more activity opportunities in catchment areas. However, the high cost of construction and operation has become an important factor hindering the development of urban rail transit, especially in developing countries. Reliable measure of residential property appreciation can provide suggestions for rail transit planning and policy-making of value capture to fund rail transit. Despite numerous studies on the value-added of housing price in catchment areas, there are few studies on the relationship between the value-added of housing price and accessibility. In this research, we aim to investigate whether there is a significant relationship between urban rail transit network accessibility and residential property appreciation around each station and how such a relationship varies over time. We employed a generalized-travel-cost-based accessibility measure to capture the residential property appreciation using residential property price data of 2014 in Shanghai. The results indicate that there is a positive correlation between the rail transit network accessibility and residential property appreciation. Both of the accessibility improvement and residential property appreciation are bigger in suburban areas and smaller in city-center areas. This method can provide reference for urban rail transit planning and transit-oriented development.

This investigation draws on the expertise of urban rail transit vibration damping track, based on the theory of vehicle-track coupling dynamics, systematically studied the impact of the change in the stiffness of the damping fastener on the vehicle when the 200 km/h high-speed railway track adopts fastener-type damping measures. And the influence law of the dynamic response evaluation index of the track system; the usability of the stiffness value of the typical vibration damping fastener of urban rail transit in the high-speed railway is evaluated; the reasonable value range of the stiffness parameter of the high-speed railway vibration damping track is proposed. Studies have shown that when rails with fasteners are used in high-speed railways, their stiffness should not be lower than 15 kN/mm. Although they have a certain suppression effect on environmental vibration, their vibration reduction effects are much lower than those of urban rail transit fasteners. The damping effect of the damping measures.

A multi-stack fuel cell hybrid power system architecture including three fuel cell systems and a battery is developed. The efficiency analysis and calculation are carried out based on the power loss of the multi-stack FC system. This paper proposes a two-level multi-stack coordination energy management strategy which consists of multi-stack FC system control level and multi-stack FC/Battery hybrid system control level. The method of multi-stack FC system control level is based on maximum efficiency range for a multi-stack fuel cell system to achieve high efficiency. The coordinate control of multiple power sources realizes the effective distribution of demand power, avoids the transients and rapid changes of demand power, and enhances the overall efficiency of the system. A hybrid system model is built and the proposed strategy is evaluated with a real driving cycle. The results of the proposed strategy show promising improvement in the overall performance of the system.

The action principle of a certain type of coupler draft gear system under longitudinal braking pressure is analyzed. Both the dynamic safety index of wheel-rail at the same braking speed and different free angles of coupler are studied. The influence of swing angle of coupler on wheelset lateral forces are simulated based on the dynamic theory. The results show that, for the marshalling train mode, the wheel-rail dynamic safety index meets the operation requirements as the maximum free tilt angle of coupler is 3°. Once the maximum free tilt angle of the coupler reaches 4°, the wheelset lateral force can’t meet the requirements of safe operation. The longitudinal compressive force and the reset function of coupler have effects on the locomotive flange wear.