Advances in Dynamics of Vehicles on Roads and Tracks III

The axle-box bearing is a crucial component of rail vehicles, and its service condition has a direct impact on the safety and stability of the entire vehicle system. Envelope spectrum analysis based on spectral coherence (SCoh) is an effective tool for revealing the underlying periodic mechanism caused by bearing defects. The improved envelope spectrum (IES) via Candidate Fault Frequencies Optimization-gram (IESCFFOgram) provides an efficient approach for identifying frequency bands without relying on sparsity indicators or fault characteristic frequency. However, the applicability of the IESCFFOgram is limited to the analysis of vibration signals with a single frequency band. Therefore, a new method referred to as combined IES (CIES) is proposed based on candidate fault frequencies to generate a spectrum tool carrying diagnostic information dispersed in multiple frequency bands. The proposed method is tested and validated using axle-box bearing datasets from a test rig. Comparisons with state-of-the-art methods demonstrate the superiority of the proposed CIES method in identifying multiple informative frequency bands under complex operating scenarios.

This paper presents recent advancements in the modeling of long train-track dynamics, specifically addressing the challenges associated with simulating long track sections. The research, initiated in 2017, has been presented at various conferences including IAVSD 2017, IAVSD 2019, and IAVSD 2021.Initially, a method for modeling three-dimensional (3D) long train dynamics was proposed and successfully achieved. Subsequently, a short track model was developed and validated, leading to further investigations for modeling comprehensive long track sections.To overcome the limitations of existing track dynamics models, this paper introduces an innovative parallel computing approach. The proposed method divides long track sections into shorter segments, which are concurrently solved using parallel computing techniques. Each shorter section is assigned to a dedicated computing core, and interaction between adjacent sections is established through boundary conditions. Additionally, a loop-track method is employed to model infinitely long track sections. The track models incorporate four layers of structures: rails, sleepers, ballasts, and sub-ballasts. The rails are modeled using the Finite Element method, sleepers as rigid bodies with six degrees-of-freedom, and ballasts and sub-ballasts as interconnected elastic blocks.

Railway in-train forces are vital for evaluating multiple aspects of rolling stock. Conventional methods necessitate substantial investment in manpower and expertise, while only gathering data for specific service conditions one at a time. This paper presents a predictive machine learning approach for railway in-train forces, using data collected from automatic train operation (ATO) systems. The proposed method employs longitudinal train dynamics simulations (LTSs) to establish the correlation between ATO measurements and in-train forces. Subsequently, a self-attention-based convolutional neural network (SA-CNN) is trained to forecast the histories of in-train forces. Results demonstrate that the well-trained SA-CNN model exhibits superior compatibility with arbitrarily combined inputs while reducing computational time. The proposed approach holds promise for quick and reliable in-situ monitoring of railway in-train forces, benefiting research on in-train forces and industrial applications.

High-pier railway bridges are widely used in mountainous areas with complicate, rugged and dangerous landform. Due to the large spatial flexibility of the high pier, the wheel-rail dynamic interaction may become more intense under the combined action of the train dynamic load and the non-stationary seis-mic wave, which may cause greater deformation and impact on the train-track-bridge (TTB) coupling system. In order to study the structural dynamic characteristics and traffic safety of such a complex and large-scale system under earth-quake conditions, this work proposed a train-track-high pier bridge (TTHPB) spatial coupled dynamic model and verifies its the accuracy and reliability by comparing with published literature. In this model, the multi-rigid-body train, the elastically point supported Euler rail, the Mindlin track slab considering shear deformation, and the finite element model of the high-pier bridge with variable cross-section continuous beam and tapered hollow pier are properly considered. In the simulation of the ground motion, traveling wave effects, soil conditions and coherent effects are comprehensively considered, and the corresponding acceleration time history sequence is generated for each support position of the high pier bridge by spectral method. The influences of the pier heights and train speeds on the train running safety are systematically investigated. This work provides theoretical reference for the design of high pier bridges and the speed of trains passing through the bridge in earthquake prone areas.

Recent years, the failure of the upper arm has occurred frequently. Inspired by the structural failure of the pantograph, the load asymmetry of the pantograph upper arm is found and the reason is analyzed based on the test in laboratory. What’s more, a methodology is proposed which can be used for efficiently calculating the spatial load of internal hinge joint of the pantograph, while also considering the dynamic calculation of the pantograph catenary systems dynamics interaction. Firstly, the multi-rigid body model (MRBM) is established, secondly, based on the MRBM, and the modal reduction, the degrees of freedom of upper arm and collector head guidance are improved to effectively reflect the spatial loads. Finally, validation of the improved model is performed by comparing it with widely used MRBM of pantograph.The improved model aims to obtain the contact force of pantograph-catenary system and internal loads of the pantograph, which can be used for calculating the fatigue strength of the internal structure and compiling the load spectrum.

The non-contact detecting method of the pantograph and catenary (PAC) system has been the subject of many studies. However, there are only a few different types of research on the non-contact estimation method of the PAC system’s contact force. As a result, this study introduces a non-contact approach for measuring contact force between pantograph and catenary (PAC) using image processing and the Kalman Filter. A non-contact contact force of PAC detection method which simply requires the vertical displacement of the collection head is proposed. A PAC contact force identification method is built based on the improved Kalman Filter and the PAC dynamics model, which is used to obtain the vertical displacement of the pantograph’s collector head. Only the vertical displacement of the collector head as determined by image identification is used to estimate the contact force. It might assist with the engineering application of contact force online monitoring.

Ensuring reasonable pantograph dynamic parameters is crucial for maintaining pantograph-catenary (PAC) matching performance and reducing maintenance costs. Initially, a dynamic model of PAC, accounting for the rolling motion of the collector head, was established, which is utilised to calculate the contact force of the PAC, acceleration of the collector head, and contact force distribution coefficient along the strip. Additionally, the objective function of optimization is established. Subsequently, the sensitivity of pantograph parameters is investigated using the modified Morris approach, and three optimal parameters are selected in accordance with engineering practice. Finally, the pantograph parameters are optimized by using the PAC dynamic model combined with a genetic algorithm. The results demonstrate that the equivalent mass of the collector head and lower frame are the most sensitive, and the optimization processes significantly improve the dynamic interaction quality of PAC.

In order to solve the vehicle transverse swing problem in the railway turnout, this paper discussed the influence of curved switch rail on vehicle transverse swing through field testing and numerical simulation. A vehicle-turnout coupled dynamics model was established to evaluate dynamic responses, and the reliability of the proposed model was verified by comparing with the testing data. The influence of worn curved switch rail on the running safety and stability was proposed. Conclusions include: (1) According to field testing, lateral acceleration of train body reached 0.8 m/s2 and −0.5 m/s2 in the diverging route; (2) Simulation results show that the dynamic performance in the switch panel has a significant effect on the running quality, and abnormal wear of curved switch rails leads to lateral acceleration increasing from 0.71 m/s2 to 1.34 m/s2, which makes vehicle transverse sway drastically; (3) Wheel-rail friction coefficient affects the development of rail wear and the coefficient range of 0.35–0.40 is inappropriate in the turnout.

Due to the reliance of a permanent magnet levitation vehicle on repulsive forces for suspension, any displacement or misalignment of the magnets generates lateral forces. When a train traverses a curved track segment, the centrifugal force causes the vehicle body to shift towards the outer side of the curve, resulting in lateral forces between the magnets. These lateral forces also direct towards the outside of the curve. If measures are not taken to counteract this trend, the lateral forces increase with the increasing lateral displacement of the magnets, compromising the stability of the vehicle and affecting its safety. To address the issue of guidance safety in permanent magnet suspension trains, a hybrid guidance system that combines mechanical guidance wheels and electromagnetic guidance is proposed, and Active Disturbance Rejection Control (ADRC) is used to control the hybrid guidance system. Comparative analysis of the vehicle dynamic performance under the traditional mechanical guidance wheel guidance and the hybrid guidance system under curved track conditions is also conducted.

As railway vehicles become faster and lighter, the vibration of car body tends to increase and that makes the ride comfort worse. In lateral and vertical rigid-body vibration, a number of reduction technologies have been put into practical use, such as semi-active suspensions and variable vertical dampers installed between car body and bogie. In elastic vibration, various methods have been studied, such as control by previously mentioned dampers, stack-type piezoelectric actuators. However, these methods focused on only the bending vibrations, it has been difficult to reduce multiple elastic vibration modes simultaneously. The authors propose a method to simultaneously reduce multiple elastic vibration modes, including torsional vibration, by controlling internal pressure of air springs. Since this method uses existing devices, it is superior in weight, cost, and maintenance compared to installing a new vibration compensator. First of all, we developed railway vehicle analytical model that can express elastic vibration including torsional vibration. Furthermore, we designed a control system by H-infinity methods and verified vibration-reduction effect on the stationary excitation test of simple railway vehicle model. As a result, it was confirmed that multiple elastic vibration modes, including torsional vibration, can be reduced simultaneously.

An unsupervised machine learning algorithm is developed to evaluate the rail track stability and detect potentially unstable track segments using on-board Doppler LiDAR velocity measurements. The measurement system includes four Doppler LiDAR velocity sensors that can record small variations in the lateral and vertical velocities of the left and right rails. Extensive tests are conducted in a controlled environment on the high-tonnage loop (HTL) at Transportation Technology Center (TTC). The system is mounted on a loaded car measuring left and right rails’ velocities at various forward speeds. To evaluate the performance of the model, a weak lateral condition is simulated in a section of the High Tonnage Loop (HTL) at the TTC. The results show a promising detection of the small amount of gage widening that occurs in the section of the track that is doctored to have weak lateral resistance.

Currently, numerous single-track railway lines are disused due to economic reasons. They could be reactivated by small vehicles that use only one rail and thus can be operated in both directions at the same time. MONOCABs are such small cabin-like vehicles, stabilized by a system of control moment gyroscopes and a trim mass. They could make an important contribution to improve the mobility offer especially in rural areas. Regarding the MONOCAB, there is currently no reference in comparison with other vehicles. In the context of mechanical design and construction, interdependencies with vertical stabilization occur. Torsional effects in particular can critically affect the stability. This paper investigates the influence of mechanical eigenmodes on the vertical stabilization system. Specific characteristics of the system (especially due to the gyroscopes) are highlighted by a model-based analysis. Moreover, a FEM modal analysis is used to examine the supporting frame of the vehicle. The results are compared to experimentally estimated frequency responses of a full-scale monorail vehicle.

As a critical factor in the degradation of rails and wheels, wheel-rail contact heat has been investigated with various analytical and numerical methods. However, the predicted temperature distributions and thermal loads have not been directly validated through measurements due to the challenges associated with accurate measurements. This study employs an infrared camera to measure the temperature variation at the wheel-rail contact under various slip ratio conditions in an in-house wheel-rail dynamic contact test rig. Wheel braking is replicated, and a wheel flat is generated. The temperature field of the contact interface is measured and analyzed, revealing the heating and cooling processes before and after the formation of the wheel flat. The results demonstrate that the contact temperature between the wheel and rail progressively increases with increasing slip ratio until a flat is formed. Notably, at a slip ratio of 8.3%, the observed contact temperature reaches 337.2 ℃ and then rises to 432.8 ℃ at a higher slip ratio of 15.9%. When the wheel flat is generated at a slip ratio of 20.4%, the observed contact temperature between the wheel and rail reaches 652.4 ℃. After the formation of the flat, the contact temperature initially decreases due to more wheel material of lower temperature entering into the contact and rises again with the increase of slip ratio. These measurement findings are valuable for calibrating and validating simulation models and investigating thermal damage related to wheel-rail interactions.

Abnormal vehicle shaking will seriously affect the passenger’s riding comfort. In order to solve the problem of abnormal tail-car shaking of 160 km/h centralized power EMU passing through the tunnel, the characteristics of tail-car vibration, the trend of external pressure difference and the transmission characteristics of suspension vibration were analyzed through line test, and the main influencing factors were determined. In order to further study the mechanism of this phenomenon, a vehicle system dynamics model containing nonlinear suspension elements was established, the actual performance of suspension elements under different body motion states and the influence of different performance on the body modes were analyzed, and the phenomenon was suppressed by some means. The results show that when the tail car passes through the curve, the shaking mode of the car body changes under the action of the lateral stop, and the coupling with the air turbulence outside the car when passing through the single-line tunnel is the root cause of the abnormal shaking of the car body. By adjusting the suspension of the second series, the abnormal rocking phenomenon can be effectively suppressed, and the dynamic stability of the rear control car can be greatly improved.

Ensuring the integrity of high-speed (HS) trains is essential for their large-scale and long-term safe operation. This paper presents a generic framework for defining and assessing the integrity of HS train systems in which vehicle system dynamics play a central role. First, the concepts of structural integrity, dynamical integrity, and system integrity of HS trains are defined. The system integrity relies on the structural integrity of train components and the dynamical integrity of the whole vehicle system. The dynamical integrity directly affects the dynamical performance of HS trains as well as the degradation and failure of train components. Then, the general strategies for assessing the structural integrity of HS trains and the general principles for assessing the dynamical integrity of HS trains are discussed. Further, numerical, experimental, and operational approaches for assessing the dynamical integrity of HS trains are introduced, including coupled dynamics theory, tailored test benches, and monitoring and prognostic methods. These theories and practices effectively support the integrity assessment and safe operation of HS trains in China.

The maintenance of a railway network is a complex process that is associated with high costs. The main causes for regular maintenance measures are profile wear and rolling contact fatigue (RCF). To help in this planning, state-of-the-art models of the use extensive multi-body simulations (MBD) to consider the influence of the vehicle fleet. This is very time-consuming as the complexity of the proposed models and the related degrees of freedom seem endless. Still, they have difficulties in predicting results from the real operations. In this paper, a hybrid approach is presented. The main objective is to use as few as possible MBD simulations to scale the wear, measured for one scenario (e.g. curve radius, vehicle fleet), and then apply it to a different scenario. The same MBD simulation results are also used as input for RCF prediction, i.e. crack initiation. This calculation is even more time consuming than the MBD simulations, since it requires a new simulation for each combination of vehicle types on each track section. This information is rarely known and often requires time-consuming parameter studies. Therefore, a new methodology is proposed, which calculates the crack initiation for each vehicle types separately. The results are then combined in post-processing for the whole vehicle fleet on the selected track section. This makes it possible to predict wear and RCF not only section-wise but on a whole network with acceptable effort.

Tokyo Metro has developed a special bogie (PQ* monitoring bogie) that can monitor the forces between wheels and rails and derailment coefficients on the service line. At the same time, in service lines with sharp curves, Tokyo Metro has also introduced a steering bogie that directs the wheelset in the radial direction of the curve with linking the bolster and axle box. And to modify this steering bogie into a PQ monitoring bogie, we performed simulations and various actual vehicle tests. This study reports the results of these developing tests and practical applications.PQ*: In Japan, character “P” means the character “V” (Vertical Force) and character “Q” means the character “L” (lateral Force) in general. Then derailment coefficient L/V means Q/P in Japan.

In order to achieve effective lubrications of wheel/rail contact area, a method of detecting sharply curved tracks where wheel/rail wear may progress is desired. The present study examines the use of monitoring bogie that can collect continuous data of wheel/rail contact forces during commercial operations. Based on the idea of friction circle, a new index is proposed, which is based on the ratio of longitudinal force to lateral force acting on the leading-inside wheel of a bogie. The relationship between the new index and leading-outside wheel wear is shown using experimental data from the roller-rig tests conducted in previous studies. Multi-body dynamics simulations are carried out to investigate the relationship between the new index and wear number. Moreover, the new index is applied to data collected by the monitoring bogie during commercial operations. The roller-rig test results, the simulation results, and the data collected by the monitoring bogie suggest that the new index could be a useful index for evaluating the leading-outside wheel/rail wear.

This study aims to investigate the causes of abnormal riding comfort (excessive and W-shaped distribution of riding comfort) in dynamic tracking tests of low-floor trams and propose appropriate improvement measures. A multibody system dynamics model of the tram is established, and the accuracy of the model is verified through a dynamic tracking test. The results reveal that the primary cause of excessive comprehensive riding comfort is due to the large amplitude of the measured irregularity and the low equivalent conicity of the wheel-rail contact relationship. The main reason for the W-shaped distribution of riding comfort is the weak inter-vehicle constraints and the lack of lateral energy-absorbing devices. Based on these findings, the following measures are recommended to improve riding comfort: (1) reducing lateral stiffness of the secondary suspension, (2) modifying structural parameters of the M3, (3) modifying the joint type between TP2 and M3, (4) introducing a damper between the middle car. By taking these measures, the riding comfort of low-floor trams has been effectively improved.

With multiaxial fatigue model and rigid-flexible coupling dynamic model, the effects of polygonal wave amplitude, running speed, and axle load on multiaxial fatigue damage of high-speed train axle are studied considering wheel polygonization. The results indicate that an increase in polygonal wave amplitude will lead to an increase in the maximum and range of the axle’s stress components, thereby reducing the service life of the axle. When the frequency excited by wheel polygonization is near the modal frequency of the wheelset, the dynamic stress of the axle is higher than the allowable safety stress, and the service life of the axle is much lower than the design life. The axle load will affect the service life of the axle by affecting the maximum dynamic stress. Under the condition of wheel polygonization, appropriately reducing axle load can greatly improve the service life of the axle. Therefore, to ensure operation safety, the influence of wheel polygonization should be fully considered in the design stage of the axle.

The maglev train, running at high speed, needs sensorless control to estimate the speed and position based on calculating the pole phase angle of the long-stator linear synchronous motor (LSM). This article proposes a novel sensorless control strategy using extended full-order state adaptive observer. The nonlinear model of LSM is established, taking into account the variation of vertical and longitudinal freedom parameters. Then, an extended full-order state adaptive positon observer is designed on the fusional basis of full-order state observer and extended state observer, which settles the delay problem of non-ideal control element at high speed. Furthermore, optimizing speed regulator to achieve efficient decoupling control of dynamicity and stability for the problem of tracking delay and load disturbance, through analyzing the influence of feedback gain, observer adaptive parameter, speed regulator parameter adjustment on the sensorless control system. The average estimation error is limited to 0.2rad at maximum speed. And the control effect is improved. Theoretical analysis is presented, and the proposed approaches are verified by experiments on Rt-lab, a semi-physical simulation platform.

The guiding principle of rail vehicle is explained. Based on the principle, the main factors affecting the wheel guiding force are presented. Then the contact geometry of S1002/UIC60E2 is analyzed. It's shown that the radius of flange of wheel profile S1002 is smaller than the corner of rail UIC60E2. Therefore, the two-point contact between the wheel and rail is observed, which decreases the longitudinal creep force and increases the wheel guiding force, so that the risk of derailment is increased consequently. To improve the curving performance of S1002/UIC60E2, a new method optimizing wheel profile for the targeted wheel/rail contact geometry is presented. The optimized wheel profile with this method can avoid the two-point contact problem and improve the curving performance by decreasing the wheel guiding force. A computer program based on this method has also been developed. The curve negotiation test on track by DBST showed that the wheel guiding force of the optimized wheel profile decreased significantly.

Articulated device is the component that transfers various loads between adjacent vehicle bodies of virtual track train. In the actual application of virtual track train, the failure rate of the articulated device is high and the service life is short. In this paper, taking the three module with six axis virtual track train architecture as an example, based on the extended Ackerman steering tracking strategy and optimal course guide strategy, a virtual track train dynamics joint simulation platform is established through SIMULINK and SIMPACK. Through dynamic simulation analysis, it is found that the tracking effect of the optimal course guide strategy is superior to the extended Ackermann steering tracking strategy, but no matter which tracking strategy is used, the lateral stiffness of the articulated device has a certain impact on the tracking performance, dynamic performance and articulated device load of the virtual track train. When the lateral stiffness of the articulated device is 5 $$\times$$ × 104 ~ 1 $$\times$$ × 105N/m, It can basically achieve the balance and consideration of tracking performance and dynamic performance, and reduce the lateral load borne by the articulated device.

The results of theoretical investigation of dynamic qualities for high speed passenger trains of articulated and standard types are given. The cars of both trains are equipped with wheels with different tread profiles used by Ukrainian and European railways. The new wheel tread profile is proposed. The developed profile ensures the compatibility of the wheel with the rail under the transition of passenger trains from one track to the other under the joint operation at these railways. It is also shown that when using the proposed wheel profile in passenger cars under the conditions of joint operation of trains on Ukrainian and European railways, improved characteristics of their interaction with the track will be provided. It will contribute to the reduction of wheel flange wear and the increase of wheels resource features according to this criterion. The influence of the developed wheel tread profile on the considered trains car dynamic qualities is estimated.

In order to verify the accuracy of levitation chassis dynamics model of high speed maglev, the flexible vibration of the levitation chassis is explored, and the finite element model of levitation chassis is established to calculate its elastic mode; then the flexible-rigid dynamics model of the high-speed maglev vehicle is built. According to the field test data from Tongji University's maglev test line, the influence of flexible vibration of levitation chassis is analyzed on the gap of guidance and levitation electromagnet. The comparison with the simulation demonstrates that the results from the model of the levitation chassis flexibility is more close to the test results. The main frequencies of the vertical and lateral levitation chassis vibration are 10.4 and 13.2 Hz respectively, which are similar to modal frequencies of relative pitching and anti-phase yawing between the front and rear levitation frame. The flexibility of levitation chassis should be taken into account in the key issues of high-speed maglev trains, such as control parameter optimization, suspension parameter optimization, and running stability.

Rail inclination is a well-known important track design parameter. It may have a measurable influence on the running dynamic behaviour of railway vehicles, as it affects equivalent conicity. Their effects are clearly visible when training Machine Learning (ML) algorithms for different purposes. This has been observed in on-going research regarding the detection of rail alignment using computer vision for in-service condition-monitoring.This paper briefly summarises the condition-monitoring research, and goes into detail regarding the effects of inclination and conicity explained from a vehicle dynamics viewpoint.

To study the tread surface hardness difference that caused by wheel diameter difference of wheelsets, an investigation on corresponding factors of wheelset hardness was done. A group of data including wear rate, wheel diameter, wheel rim hardness and tread hardness was collected to serve as the dataset for neural network. Improved extreme learning machine (ELM) based on particle swarm optimization (PSO) algorithm was chosen to be the main method, trained by dataset and used to predict the tread surface hardness difference. The result shows that PSO-ELM is able to describe the changing trend of tread surface hardness difference, and reaches the best correlation level compared to the original ELM and BP network. Finally, the trained network was applied to analyze the relation between tread surface hardness difference, revealing that the rolled steel is a less sensitive material than the casted steel when meeting hardness or diameter difference.

Based on the Independent component analysis (ICA) algorithm in unsupervised learning, this paper deeply mines the latent statistical information of the dynamic response of the high-speed train bogies and realizes the independent component extraction of the measured loads and stresses of the line. In this paper, the independent components of structural loads and fatigue critical point stresses under three tests covering different operation variables are obtained. By comparing the independent components between loads and stresses, it is found that the independent component correlation of the vertical loads and the fatigue critical point stresses is significantly higher than that of the lateral loads, reaching a strong correlation level. Meanwhile, the different operation variables tested do not affect this conclusion. This conclusion can establish an underlying connection for the structural dynamic responses of the high-speed train and provide a new basis for the life optimization and assessment of the fatigue key structures.

This paper designs an optimal reference trajectory for trains. The proposed trajectory complies with speed, acceleration, and jerk limitations. Moreover, it provides the minimal distance between the waypoints on which the speed and acceleration of the train are imposed. Using a specific first integral of the system, it constructs a piecewise-linear (with respect to distance) acceleration profile that verifies the specified jerk constraints. The resulting trajectories are concatenated respecting a specific switching policy depending on the phase-plane position of the initial and final points, and on the acceleration constraints considered for traction and braking. Using these tools, we provide a complete characterization of the points that can be connected, respecting the constraints imposed on the system. To translate the proposed strategy into a distance-based framework, we integrate backward from a stopping point to propose a running profile towards the next station. It is important to stress that all the provided results are analytic and, thus, compatible with a real-time implementation.

In this work, the measurement of instrumented wheelsets is analysed using advanced dynamic models that consider both the wheelset flexibility and the inertial effects associated with its rotation. The results show discrepancies between the simulated response of the instrumentation for the static case and that obtained through the dynamic model. These discrepancies become more pronounced as the vehicle speed and/or the frequency of the force in the wheel-rail contact increase. The more advanced model predicts that resonance frequencies depend on the angular velocity. This effect makes it challenging to develop instrumented wheelsets capable of measuring beyond the natural frequency of the first bending mode.

The track geometry irregularity has a crucial effect on in dynamic characteristics of vehicle-track coupling system, and its long-term degradation prediction is of important value to railway maintenance. In this paper, a data-driven prediction method is proposed, aiming to infer the future track irregularity for several months based on historical measurements. According to the characteristics of the track irregularity, an end-to-end model based on convolutional long short term memory (ConvLSTM) was established. An advanced spatiotemporal loss function is introduced to accurately evaluate the error between predicted and actual results. The track irregularity measurements set of a heavy haul railway segment in China for 9 consecutive months were prepared to participate in the training and testing of the network. The results show that the proposed method demonstrates elegant prediction performance. This work offers a promising path to the evolution prediction of track irregularity, and provides a methodological support for reducing the risk and maintenance cost of railway transportation.

Air brake operations can generate large values of compressive in-train forces, which can eventually be related to an increase of the derailment risk. Longitudinal train dynamics (LTD) simulations are commonly run to compute the in-train forces. However, typical LTD codes are not able to calculate the wheel-rail forces, which are needed for the evaluation of the safety indexes defined by the international standards. On the other hand, wheel-rail contact forces can be easily determined by means of multibody (MB) codes, but MB simulations of whole trains including many wagons are usually too expensive from a computational point of view. The present paper proposes to obtain metamodels of a single wagon built via kernel-based regressions, trained from the results of LTD and MB simulations of freight train air brake operations. Typical wagons running in Europe are considered as reference vehicles in the simulations. The derived metamodels are closed-form models that can be included in common LTD simulators for a fast evaluation of the safety indexes directly from the main outputs of LTD simulations of braking operations.

A mixed train, where trains with different speeds run on the same railway, is a common practice. This paper focuses on optimising a catenary system for mixed trains with varying speeds. The objective function used to achieve this optimisation is the total standard deviation of the contact force. The goal is to enhance the current collection quality and minimise contact wear. To optimise the catenary system, the particle swarm-simulated annealing (PSSA) algorithm was applied. Several improvements were made to the algorithm. Firstly, it avoided redundant finite element method (FEM) simulations by eliminating duplicated input parameters. Additionally, before lowering the simulated annealing temperature, the model with the worst performance was removed, allowing for greater chances of discovering the global optimal solution. To evaluate the effectiveness of the structurally optimised design, a comparison was conducted between the contact force standard deviation of the optimised system and that of the original unoptimised system. The results of the optimisation showed a significant reduction of 69.8% in the standard deviation of the contact force compared to the benchmark system.

In this work a detailed metallographic analysis of squats is performed and assessed. The used rail samples with squats are taken from tracks of the Swiss Federal Railway (SBB). They involve different rail materials, track layouts as well as squats at various stages of their evolution. Consequently, early stage “mini” squats are examined. A fully-developed squat is opened along the crack face and several squats are sectioned in longitudinal or transversal direction. The sectioned cracks substantially help to understand the mechanism squat by creating a reconstruction of a squat below the rail surface. Furthermore, the residual stresses of one rail sample are analysed. The variety of investigations enables to obtain a detailed picture of squats and helps to find their root cause.

Sand in wheel-rail contacts is successfully used for a long time to increase adhesion. However, the physical effects responsible for this adhesion increase remain unclear. To improve the understanding of these effects an approach combining experiments with Discrete Element Method (DEM) modeling is followed. Results from initial breakage and high loading experiments on single sand grains under purely normal loading conditions show that the spreading behavior and the forming of clusters of solidified sand fragments depend on the type of sand and the contact conditions, namely dry and wet. The experimental data were used to develop, calibrate and validate DEM models including particle breakage. These DEM models can describe the observed effects. Finally, a systematic classification is presented where tangential relative motion due to slip can occur in a sanded wheel-rail contact. This is seen as an important basis for future experimental and modelling work.

The stability of vehicles is very important for the operation of the rail transit system. Duringa the operation, the hunting motion will occur due to the creep force and the geometric relationship between the rail-wheel, which will cause the vibration of the vehicle system and affect the safety of the vehicle operation. For the power bogie with motors, the motor suspension can also have a significant impact on the hunting stability of the bogie. To explore methods to improve vehicle dynamics, firstly, the study about how to improve stability by optimizing the motor suspension to achieve the functions such as lifting the critical speed, bifurcation control, and reducing the amplitude of the limit cycle by altering the motor suspension is made. Then a study about how to further optimize vehicle stability through active control of motor suspension is also made. Finally, the research focuses on the time delay problem in active control, and the impact of this problem on vehicle stability is taken, providing a reference for the related research of vehicle dynamics.

Wheel sliding frequently occurs under poor wheel-rail adhesion status in railroad vehicles, which may cause abnormal abrasions of the wheel and rail interface. Identifying the wheel-rail adhesion status can contribute to precise anti-slip control and improving adhesion utilization; correspondingly, the abnormal abrasions can be reduced. An approach for identifying wheel-rail adhesion status based on an improved recursive Levenberg-Marquardt (RLM) algorithm is proposed, and the Polach model for tangential force calculation is used to fit the nonlinear creep force. The local gradient of objective function is modified by Hessian matrix to realize the adaptive change of the algorithm. Moreover, a variable forgetting factor based on the sigmoid function is introduced to improve to the robustness and response speed of identification algorithm. Simulation results indicate that the proposed algorithm can accurately identify the time-varying wheel-rail adhesion status under large creepage conditions.

The continuous movement of high-speed train results in the pantograph interacting with a long catenary structure. The traditional methods based on the Lagrangian description can only model the whole long catenary structure, which decreases their calculation efficiency. In this work, a reduced pantograph–catenary interaction model is developed to accurately and efficiently simulate the pantograph-catenary interaction with the long catenary structure. In the model, the long catenary is reduced to a small region around the moving pantograph, and the arbitrary Lagrangian‒Eulerian (ALE) method and modal superposition method (MSM) are used to model this small area. The pantograph is modeled as a multi-rigid body system. The pantograph and reduced catenary model formulate the reduced pantograph–catenary interaction model. Because the long catenary structure is reduced to a small moving region, the number of degrees of freedom (DOF) of the model is significantly decreased. The present model is validated by the EN 50318:2018 standard with a long catenary structure considered. The calculation results show that the present model is accurate and efficient in the investigation of long-term pantograph-catenary interaction dynamics.

When the straddle monorail vehicle passes through the curve, the guiding stiffness of the steering assist device(SAD for short) and the resistance stiffness of the secondary suspension cancel out each other, which is conducive to the bogie being in the radial position of the curve and reducing the tire wear. The linear model stiffness of the SAD was deduced, the guiding stiffness of SAD was tested when the vehicle passed through the curve, and the error of the linear model stiffness was analyzed. The output force characteristics of the oil-gas spring of SAD were analyzed, and a simplified calculation method of the initial output force of the oil-gas spring was proposed based on radial conditions, which can be used to direct the parameters design of the SAD. Finally, the influence of different initial output force of oil-gas spring on lateral ride comfort was given by dynamic simulation. The simulation results show that the lateral ride comfort is excellent, greatly influenced by vehicle speed and less by the adverse influence of initial output force of oil-gas spring.

The high precision simulation and strength checking of the connection structure in carbon fiber reinforced plastic (CFRP) high-speed carbody is a challenging problem. In this study, a bimodulus constitutive model for braided CFRP was put forth, and the bonded/bolted hybrid joint in the carbody was subjected to submodel simulation. First, the tunnel meeting case was used to simulate the mastermodel of the CFRP carbody. The boundary conditions of the stress concentration area were retrieved. The bimodulus constitution and boundary conditions were then inputted, leading to the construction of a fine submodel of the hybrid joint. The strength, deformation, and failure factors of the bolts, adhesive layer, and CFRP plate were verified and assessed at the end. This work offers a fresh concept and methodology for the design and simulation of the CFRP connection structure in high-speed carbodies.

To accurately grasp the evolution characteristics and wear patterns of the wheel tread in the whole life cycle of high-speed train wheels, it is necessary to study an effective wheel profile prediction model. Aiming at the problem of large computation amount and long time of the traditional vehicle-track dynamics model in calculating wheel wear, this paper provides a simplified vehicle-track coupled dynamics model. Based on this, this paper studies the wheel-rail contact calculation model, and combines the dynamics model, the contact calculation model and the Archard wear calculation model to calculate the wear amount of the cell. Then, this paper uses the cubic spline interpolation calculation and the five-point cubic smoothing method to superimpose the wear amount of the cell on the wheel profile. In this process, this paper innovatively applies the method of mathematical statistics to the establishment of the relationship between the wheel rolling contact position and the lateral displacement, and discusses the distribution rules of the lateral displacement and the creepage rate. After establishing a relatively complete wheel wear prediction simulation model, this paper analyzes the effects of different working conditions such as vehicle running speed, line condition (straight line length and curve radius and length) and wheel material (hardness) on wheel wear.

Wheelset–rail rolling contact is more complex on curved track than on tangent track and is susceptible to rolling contact fatigue (RCF). This study presents an investigation of Belgrospi-like damage, features crack nests grouped periodically with short-pitch corrugation, which is a particular type of RCF that occurred on low rail of sharp curved track in a metro line in China. A 3D elastic–plastic wheelset–rail rolling contact model on curved track is developed using the finite element (FE) method to investigate the frictional rolling contact behavior with short-pitch corrugation. Emphasis is placed on solving detailed dynamic contact solutions, and inferring the consistent and differential relationships between them and the corrugation geometry to further analyze the causes of Belgrospi-like damage. It is found that the wheelset–rail frictional rolling contact induced by short-pitch corrugation is more likely to damage under rolling–slip conditions on low rail of sharp curved track. Consistent patterns of high dynamic vertical and longitudinal contact forces, Von-Mises stress, contact pressure, and surface shear stress are subjected to be responsible for Belgrospi-like damage initiation before the crest. The causes of Belgrospi-like damage were initially estimated, but need to be further monitored to prevent their development from affecting railway operations and maintenance.

The CONTACT software for wheel–rail contact evaluation is extended to support rails with a varying cross section. The extension involves novel tensor spline techniques for 3D geometry representation, and extension of the existing contact search methods to work on the full 3D rail geometry without resorting to a locally prismatic approximation. The resulting software is integrated in the NUCARS software for vehicle–track interaction. Results are presented for one of the recent benchmark cases on switches and crossings.

This paper proposes a control strategy for active lateral secondary suspension that uses preview data. Based on a derived analytical model a model predictive controller (MPC) is implemented. The influence of the track ahead upon carbody lateral dynamics is considered explicitly.The controller developed is applied to a full-scale rail vehicle model. Ride comfort is evaluated according to EN 12299. Multibody simulations show that on tracks with small radius curves there is a significant increase of continuous ride comfort.

The continuous development of hollow wear on the wheel tread of railway vehicles can decrease vehicle stability. In order to improve vehicle stability and ensure traffic safety, an optimization method for vehicle stability is proposed. In this method, the mapping relational model between the hollow worn parameters and the equivalent taper is established to obtain the hollow worn parameters characteristics corresponding to the low equivalent taper, and then the vehicle dynamics parameters are optimized to improve the evolution results of the tread hollow wear. Finally, the vehicle stability is improved. After optimization using this method, the wheel equivalent taper of the vehicle running 129,000 km decreased by 16.39% compared to before optimization, and the maximum lateral vibration acceleration of the frame also decreased by 32.02% compared to before optimization. In summary, this method can effectively improve vehicle stability and provide a reference for solving the problem of stability degradation caused by tread wear on high-speed trains.

Potential manufacturing defects and dynamic loads in the service could introduce cracks in the bogie frame. These cracks, in turn, can vary the stiffness matrix of system, thereby the variations in dynamic behaviors of bogie frame. This study thus investigated dynamic behaviors of a bogie frame in the presence of fatigue crack through a field test and a numerical model. In the test, the axle box vibrations were measured, which serves as the excitation of the numerical model of bogie frame. Subsequently, a rigid/flexible coupled dynamic model of vehicle was developed, considering the flexibility of bogie frame. A methodology, based on the equivalent spring and contact elements, was developed to model fatigue cracks in the dynamic model. This enables us to simulate coupling behaviors between the vibration and the crack propagation. Upon the proposed model, the evolution of dynamic behaviors of bogie frame considering the crack propagation process was studied under the services loading. The results show that the cracks significantly alter the vibration behavior of the bogie frame, leading to a noticeable response in the high-frequency components. This facilitates further research on crack damage detection and localization. The dynamic stress intensity factor (DSIF) obtained through displacement extrapolation method accurately describes the dynamic propagation behavior of crack tips. This helps us understand the crack propagation models better, thereby the estimation of residual fatigue life of bogie frame.

Railway digital twins (DTs) are multi-physics dynamic models of rail vehicles that feature feedback from wayside or vehicle on-board sensors, enabling fine-tuning and calibration of the dynamic models to accurately simulate the physical system behaviour. The current DT implementation concept is typically asynchronous, given the intense computational power requirements of multibody dynamic simulations, thus limiting potential applications that could improve safety and efficiency of railway systems. This paper presents a real-time digital twin implementation concept for railway systems, including a faster-than-real-time multibody dynamics simulation of a railway bogie model and a 1:4 scale physical bogie rig provided with an axle box acceleration sensor. The real-time DT was able to recreate the dynamics of the bogie throughout the experiment. The developed real-time DT enables systematising the platform requirements of physics-based vehicle system dynamics models for DT architectures and opening the discussion on their possible practical application areas.

This paper briefly elaborates on the hunting stability problem of railway wagons, investigates the destabilization, re-stabilization mechanism and trigger conditions in the hunting stability problem, carries out hunting stability research in dynamics simulation, rolling test rig and line test, reveals the essence of the hunting stability problem, and takes another step forward in the understanding of the intrinsic factors and relationships of hunting. Directional recommendations for hunting stability research are presented.

Axle box bearings (ABBs) are a vital component of a railway locomotive and the reliability determines the operation safety of locomotive. In order to grasp their dynamic behavior during operation, this work theoretically deduces a locomotive–track longitudinal–vertical coupled dynamics model (CDM) that considers detailed dynamics of the ABBs. The model takes into account many complex interactions such as nonlinear contact and friction forces inside the ABB, wheel–rail interactions, and track irregularities. The ABB is coupled with the wheelset and bogie frame separately at each end, thus enabling the integration of the ABB into the locomotive system and a comprehensive study of its dynamic behaviour during the acceleration condition. The results demonstrate that the dynamic interactions within the ABB become more intense as the running speed increases during acceleration, the peak value of contact force between the inner and outer rings increases. Furthermore, as the locomotive speed increases, the traction force decreases, the vertical displacement between the inner and outer rings does not change much, and the longitudinal relative displacement decreases. As a result of this work, it is clear that the operating conditions of the locomotive should be suitably considered in the dynamic assessment, operation and maintenance of locomotive ABBs.

The study compares the accuracy of contact-based profilometers, namely, MiniProf and non-contact laser scanners for capturing wheel and rail profiles in vehicle-track interaction. While contact-based profilometers provide highly accurate measurements, they require trains to stop. Laser scanners, though less precise and reliable, can continuously gather profiles over a short period. The simulation results showed satisfactory agreement between laser-scanned and MiniProf profiles for the examined Y/Q ratios. Further research on processing techniques for raw laser scanner data could potentially enhance the usability of laser-scanned profiles for more in-depth contact analysis.

The virtual track train is a kind of new medium capacity rail transit vehicle. In this paper, the main architecture form of the virtual track train is introduced. And the three modules with six axles virtual track train is selected as research object. Its dynamic model is created by using SIMPACK software, and the influence of the road surface irregularity and running speed on the tyre vertical load is studied. At the same time, the finite element model of the asphalt pavement is created by using ABAQUS software. The tyre vertical load from dynamic calculation is applied to the finite element model of asphalt pavement as an external load, so as to study the relationship between rutting evolution and train running speed.

Load assumptions for the design and evaluation of fixed railway crossings are mostly based on normative guidelines and impact force calculation formulas like the Jenkin’s equation. This approach may be appropriate for the principal technical design of a traditional fixed railway crossing with analytical methods. If the assessment of a cast manganese monobloc crossing is done by a FEA model, it is concluded that the assumed impact load and the load position have a significant effect on the obtained local stress results. These two factors are mainly influenced by the wheel-rail contact interface. Therefore, the correct determination of this important input data for performing a FEA of a fixed crossing is not possible without further investigations of the wheel and crossing geometry combination. As a result of this knowledge, a closer examination of this topic is necessary by using MBS and FEA investigations, supported by in-track measurements using strain gauges, accelerometers and displacement sensors. Therefor this paper will address the investigation of the occurring impact loads caused by wheels in different wear conditions on a fixed crossing with initial geometry without wear. Further works will also consider the wear on the crossing side of the wheel-rail interaction geometry. The derived results can lead to an improvement of the current engineering approach and therefore create a new type of fixed crossing that will be designed in the aspect of using the maximum fatigue resistance and minimum material usage.

The superconducting maglev system has been developed as a high-speed transportation system. Superconducting coils are installed on the bogie of vehicle, and levitation/guiding coils are installed on the U-track. The superconducting maglev system is provided by the electromagnetic interaction between the superconducting coils and levitation/guiding coils, which act as levitation and guiding forces. In this paper, the characteristics of electromagnetic force are described. The dynamical simulation model is then built and the accuracy is verified by comparing it with experimental data from 200m straight maglev test line with High Temperature Superconducting. Finally, the dynamical behavior is studied under different operating conditions.

Currently, numerous single track railway lines are disused due to economic reasons. One way they could be reactivated for bidirectional on demand traffic is by small cabin-like vehicles, lateral stabilized by a system of control moment gyroscopes and a moveable mass. Regarding such a vehicle, there is currently no reference in comparison with other vehicles and no experimental experience or the like. To ensure the functionality and safety of the vehicle even before its realization, a model-based design is carried out for development, analysis, optimization and testing. This paper is focused on the co-simulation of such a vehicle that is controlled by a longitudinal control. In order to take into account the complex interaction between the longitudinal dynamics and the running gear, the entire system must be considered here including the wheel/rail interaction. Co-simulations are performed considering both the mechanical model of the vehicle and the control of the longitudinal dynamics of the overall system. The simulation results show that functionality and safe operation can be ensured by the vehicle longitudinal controls. As a result, the simulation and the measurement of the real system show a good match. By means of HIL and co-simulations, function tests could be shifted to earlier development stages, in order to accelerate the overall development.

Yaw dampers are equipped on rail vehicles to prevent the arising of hunting motion at high-speed running. Nevertheless, standard devices must respect a design tradeoff due to their detrimental action on the curving performances of the vehicle. In fact, the steering resistance imposed by the yaw dampers on the bogies during the low-speed negotiation of sharp curves increases the guiding contact forces with negative effects on both running safety and wheel/rail wear. This paper introduces a Switchable Yaw Damper (SYD), a semi-active on/off device designed to overcome the design tradeoff of yaw dampers by means of an additional controlled valve implemented to reduce the damping force during curve negotiation. The SYD has been prototyped, experimentally characterized, and modelled. To quantify the SYD influence on the curving performances of a rail vehicle, a multibody model has been introduced to simulate a set of real operating conditions. The curving performances of the vehicle with SYD have been compared with the ones obtained with standard yaw dampers. The comparison shows that the SYD damper technology is a simple and robust way to overcome the tradeoff that limits the design of standard yaw dampers.

Semi-active suspension technology can improve the overall dynamic performance of rail vehicles in different aspects and is much safer and more cost-effective than the full-active suspension for practical implementation. Magnetorheological (MR) damper is a promising technology among the other alternatives, considering its compact dimension and fast response time, which allows easy replacement of the passive damper to control vibration at a relatively high-frequency range. This work performs characterization tests of a prototype MR damper to investigate its dynamic performance. A nonlinear dynamics model is proposed to reproduce the behaviour of the MR damper, particularly on elasticity of the rubber end mounts. The model parameters are calibrated showing excellent agreement with the experimental test. Based on the accurate MR damper model, the dynamics and control of the MR damper are studied in the application of semi-active primary suspension (SAPS) to improve vertical ride comfort. The proposed control scheme can significantly improve vertical ride comfort, particularly effective in controlling car-body first bending vibration. The study on the elasticity of damper end mounts also provides suggestions to refine the property of the MR damper and improve the control effect.

The Coefficient of Friction (CoF) is an important parameter affecting acceleration and braking behavior of trains, and consequently the inter-train distance and utilization of track. To optimize operation schedules, maximize railway capacity, and realize automatic train operations, reliable measurements of the CoFs experienced by in-service trains are desirable. In this study, a train-borne measurement approach is proposed based on a torque modulation concept. It involves superimposing a small-amplitude sinusoidal signal on the motor torque. Because the wheel-rail friction force acts as variable damping, it causes a phase difference between the angular velocity response of the wheelset and the input modulated torque signal. This phase difference can be used to determine the creep coefficient, i.e., the slope of the creep curve, and then to estimate the CoF in combination with the measured Coefficient of Adhesion (CoA), i.e., the ratio between the wheel-rail friction force and normal load. Simulations of torque modulation with VI-Rail are conducted. Variation of phase difference with the increase of the modulated torque is derived theoretically and compared with numerically obtained results using the VI-Rail multibody dynamics model under different CoF conditions. The good agreement between the results indicates the effectiveness of the proposed measurement concept.

Track maintenance and preventive maintenance are necessary for the safe and comfortable running of railways. However, there is a problem that sufficient inspections cannot be performed by local railway operators with limited personnel and financial resources. In response to this problem, a track condition monitoring system was developed and applied to regional railways in Japan. In the developed system, car-body vibration is used to analyse the track condition. However, track maintenance is based on measured track irregularity at millimetre. As the car-body acceleration is not clearly linked to the track irregularity, it is difficult to use the car-body vibration for track management. Thus, it is necessary to develop a method to estimate track irregularity from car-body vibration. In this paper, we proposed a new technique for estimating track irregularities from measured car-body acceleration. Gaussian process regression was applied to the simulated data, and the obtained response surface was used to estimate track irregularities. An application example for a regional railway line showed that the proposed method is useful for track irregularity management.

The vibration of railway vehicles is commonly reduced with the use of hydraulic dampers. It is essential for the dampers to achieve the excellent dynamic performance of high speed Electrical Multiple Units (EMUs). Generally, a damper dynamics model is employed to investigate the vehicle system dynamics. Different kinds of damper models would lead to different calculation results of the vehicle dynamics. Therefore, the availability of different damper models on the accurate vehicle system dynamics simulation and damping loads calculation would be investigated. Four kinds of damper dynamics models named simplification model, Maxwell model, a new model presented by Ren and a new model developed in this paper are briefly introduced. The availability of the four kinds of damper models on the vehicle dynamics simulation are investigated. Field test damping forces of two types of high speed EMUs operated in China are presented to compare with the simulation results of the vehicle dynamics with the four kinds of damper models. It is shown that the damper model presented by Ren and the model developed in this paper are all accurate for the vehicle dynamics simulation and damping load calculation. Both the simplification model and Maxwell model have some deficiencies on the vehicle dynamics investigation and damping force calculation.

Non-conformal contact models may be inadequate for solving conformal contact problems because the assumption of the flatness of the contact patch is violated in the context of conformal contacts. Although the finite element method and boundary element method with proper modifications can be used to solve conformal contact problems, their computational efficiency limits their application. To strike a balance between efficiency and accuracy, simplified conformal contact models are preferred options. Three simplified conformal contact models have been implemented based on the modified version of the Kik-Piotrowski model, INFCON model combined with FASTSIM, and FaStrip. These models are assessed through the comparisons with results from a detailed model in terms of the contact size, shape, normal pressure, tangential stress, resultant forces, and computational efficiency. The comparative analysis of two case studies shows that the non-conformal contact model produces considerable differences from the conformal models. Among the evaluated models, the adapted Kik-Piotrowski combined with FASTSIM is the fastest, while under certain conditions its accuracy is lower than the modified INFCON + FASTSIM/FaStrip models which show overall better agreement with the reference.

Increased equivalent conicity of wheels because of hollow wear during long-term operation influences the ride comfort performance of Chinese high-speed trains. To investigate the evolution of wheel wear, a high-speed train operating on the Beijing-Shanghai Railway line at maximum operational speed of 350 km/h is monitored over a time of 1.5 years. An MBS based wear calculation software tool of KTH using stochastic simulation inputs has been used for wear prediction, where the vehicle suspension parameters and global structural modes of car-body and bogie frame have been identified using roller rig measurements and dynamic track measurements as well to validate the simulation models. The calculated wear is then validated against measurements by calibrating the wear rate coefficients. The influence of initial conicity on the lateral wear distribution is analyzed. Wheel profiles with lower initial conicities result in significantly less wear but more vibrations which possibly worsen the ride comfort. Increasing the roll-stiffness shows to be an effective way to damp the low frequency vibrations for the low conicity wheel while resulting in low wear. The suspension parameters and initial conicity which give the most stable equivalent conicity evolution and best ride comfort are selected for field tests.

High-temperature superconducting (HTS) pinning maglev has achieved rapid development in recent decades. It has a great development prospect and potential for high-speed application. The levitation system of HTS pinning maglev is mainly composed of Dewar with built-in HTS bulks and permanent magnetic guideway (PMG) laid along the line. The HTS bulks receive the pinning force in the gradient magnetic field generated by the PMG, providing levitation and guidance force for the maglev train. However, for the levitation system, there is a Dewar shell between the HTS bulks and the PMG. This conductive material will also generate eddy current in the changing external magnetic field, and affect the interaction between the HTS bulks and the PMG. The eddy current is related to the conductivity of the material. Therefore, when investigating the dynamic levitation force of the HTS pinning maglev system, it is necessary to consider the effect of Dewar shell. In this paper, stainless steel and aluminum alloy are used as the shell materials of the Dewar respectively. Through experiments and simulations, the shell materials’ influence on the Dewar's overall dynamic levitation force is explored, and suggestions are provided for the selection of HTS pinning maglev Dewar material.

Alstom’s INNOVIA 300 straddle monorail vehicle features a single-axle bogie suspended with an hourglass rubber spring. Compared to air springs, the air supply system was removed, but the hourglass rubber spring’s high vertical stiffness did not result in ideal vertical ride comfort. Consequently, we proposed an upgrade and transformation scheme for air spring suspension devices based on existing bogies without upgrading other bogie components. In addition, the steering assist device was optimized, and the adverse effects on the vehicle’s anti-overturning performance were investigated. Based on the simulation results, the critical roll angle of the car body of the air spring suspension is basically the same as with the hourglass rubber spring, and the flexibility coefficient is 10.6% higher, and the impact on the vehicle gauge was examined. Based on simulations and tests, there is a significant improvement in vertical ride comfort. The scheme can be applied to engineering applications.

The well-known Polach theory frequently used for modeling creep forces in locomotive traction studies is based on the friction coefficient dependent on slip velocity equation that was delivered with the usage of numerical experimental techniques, and it does not actually represent the background built on the physical theory developed by Kragelsky in 1948 for the description of a dry friction process at the wheel-rail contact zone. In this paper, the explanation is presented of the physical background of the friction equation and how it has been transformed to the friction modelling approach for the original Fastsim algorithm, and how it has been validated with the wheel-rail tribomachine experiment performed under dry friction conditions. The developed approach is implemented in multibody software code and creep force comparison simulations have been performed for a locomotive running under traction conditions with the developed and modified Fastsim approaches. The obtained results are presented, and limitations for the application of the developed approach are discussed.

The super rail-guided train (SRT) with four modules and six axles is one type of virtual track train (VTT). It has high carrying capacity and excellent curve passing flexibility. The core issue is achieving high path-tracking accuracy and low hinge forces simultaneously. This paper proposes a new control strategy. Firstly, the reconfigurable dynamics model of SRT is established by a two-step method, and the hinge force is quantified by vehicle state and control inputs. The control strategy adopts a layered framework. The upper layer calculates the generalized force at the centre of gravity (CG) of each module needed for tracking based on the improved model predictive control (MPC). The lower layer reallocates the CG forces, uses the ‘virtual axle’ method, and then distributes the wheel steering angle and driving torque according to the different actuator configurations of each module. The simulation results show that the proposed strategy can achieve high tracking accuracy and low hinge force and maintain robustness under different velocities and curve radii without increasing the computational press. Moreover, the control strategy can be applied to virtual track train (VTT) with different structures.

This study was primarily focused on mitigating high-order polygonal wear (PW) in China's high-speed trains. To achieve this, a fast PW trend analysis strategy and a long-term PW iterative simulation were developed. The rail localized bending modes(RLBM) were identified as critical factors influencing the amplitude-frequency and phase-frequency properties of the wheel/rail force response, which in turn contributed to the occurrence of high-order PW. It was found that the phase lag of the wheel/rail force response relative to wheel excitation played a significant role in determining the growth trend of PW. Therefore, the design of a rail-tuned dynamic vibration absorber (DVA) was crucial to manipulate the phase lag and force it out of the positive growth region, specifically between 90° and 270°. Detailed simulations found that a rail DVA with a tuned frequency of 450 Hz effectively slowed down the development of the 20th order PW (578 Hz). This research provides valuable insights into the design principles for rail DVAs aimed at mitigating periodic wear between the wheel and rail.

The longitudinal and lateral spans of the permanent magnet direct-drive (PMDD) inboard bearing bogie can be significantly reduced with the traditional bogies, providing an efficient solution for lightweight vehicles. However, the PMDD inboard bearing bogie does not need gearboxes, and the output torque of the motor directly is transmitted directly to the wheelset via a transmission hollow shaft, which could lead to the more severe electromechanical coupled vibration. Thus, the electromechanical coupled characteristics of the novel bogie should be investigated. In this study, an electromechanical coupled dynamic model of the PMDD inboard bearing bogie was established, and the model applicability was further analyzed. Subsequently, the dynamic performance of electromechanical coupled vibration was studied. The results show that the proposed model, compared with the traditional vehicle dynamic model, has better applicability to the electromechanical coupled vibration simulation. The electromechanical coupled interaction has a significant influence on the vertical vibration of the frame and motor together with the torsional vibration of the transmitted hollow shaft, especially at 6 times the fundamental frequency of currents. Moreover, the frame, motor, and hollow shaft vibrations under flux weakening control are more severe than those under MTPA control.

Particularly in recent years, railroads (transit, freight, and commuter) have been giving more attention to wheel/rail contact behavior and optimization. Both rail and wheel profiles throughout the industry have been customized to reduce wear, reduce contact stresses, increase rail vehicle lateral stability, reduce rolling contact fatigue formation, and delay corrugation onset. Custom rail profiles are implemented through rail grinding. To both aid in the prediction of level of grinding effort and ensure post grind quality, Profile Quality Indices have been developed to summarize the actual profile deviation from the desired rail profile shape (template). In North America, the AREMA Grind Quality Index (GQI) is often the standard applied. Advanced Rail Management has developed an alternative referred to as the Profile Deviation Index (PDI). By comparing these indices through case studies, their strength and weaknesses are determined, and expectations that should accompany their use is discussed.

In order to promote the engineering application of high-temperature superconducting (HTS) magnetic levitation (maglev) train and study the design requirements of the vehicle bogie in practical application. This paper investigates the dynamic response of two kinds of secondary suspension structures under the same speed and line conditions. Two air spring mounted schemes are firstly proposed, in the middle and in the end of the bogie frame. Secondly, the dynamic model is constructed and calculated in dynamic simulation software combined with the levitation-guidance force mathematical model extracted by the experiment. The simulation results show that under the same conditions, both schemes meet the requirements of relevant dynamic standards. The vertical stability of the end-mounted scheme of air spring is better in high-speed operation, while the curve passing ability of the air spring mid-mounted scheme is better. At the same time, these conclusions are also partially confirmed by the experimental test of the high-speed HTS maglev engineering prototype vehicle and test line. This work will help to better understand the design requirements of HTS maglev train, and have guidance significance for the future system engineering of HTS maglev.

China’s high-speed railway has a total length of 41000 km, of which bridges account for about 40%. The resonance mechanism of vehicles and bridges is discussed respectively. According to measured data and theoretical analysis, the (40 + 56 + 40) m and (40 + 64 + 40) m continuous girders may resonate due to the periodic load of train. And when the beam with a certain span is continuously arranged, the vehicle will also generate resonance due to periodic excitation. This paper investigated the measured natural frequencies of high-speed railway bridges and vehicles, and analyzed the sensitive wavelength of typical vehicles. For vehicle resonance, a special test is carried out by preset periodic irregularities, and the vehicle dynamic response is measured. For bridge resonance, an engineering example is provided. For the above vehicle and bridge resonance, all have been theoretically verified through train-track-bridge dynamic analysis, and the influence of resonance on the dynamic response of vehicle and bridges is systematically analyzed.

In this study, utilizing autoencoders to detect the defects of railway catenary system by contact force signal is explored. Innovatively, first, a new way to divide the signal regarding the catenary system structural units (spans) is invented and it is significant to the performance of the proposed approach. Besides, a fully-connected autoencoder with modified-embedding is built and utilized to detect the defects. And the good results show the effectiveness of the proposed approaches.

This research introduces a control algorithm based on multi-agent reinforcement learning (MARL) designed to enhance the running performance of independently rotating wheels (IRW). The algorithm’s effectiveness is experimentally validated using a 1:5 scale model. For this purpose, we constructed a dynamic simulation model of the scaled prototype and developed a training loop for a model-free controller. The front and rear wheelsets are considered individual agents, and the multi-agent deep deterministic policy gradient (MADDPG) algorithm is applied to realize distributed steering control. The proposed controller is implemented on an embedded computer within the scaled vehicle on a scaled experimental track, where the lateral displacement and attack angle of the wheelset are calculated through 3D laser profiler sensors. The experimental results show that the steering performance of IRWs on both straight and curved tracks is significantly improved when using the MADDPG controller.

The paper considers two methods of modelling a Y25 equipped freight wagon. The wagon was modelled in full, with all Lenoir links, spring carriers and plungers as separate bodies. The second was a simplified model which represented the behaviour of the Lenoir links using stiffnesses, bumpstops and friction elements only. The models were compared against industry standard assessments for derailment risk (wheel off-loading (ΔQ/Q), flange climb derailment (Y/Q) and cyclic top) as well as stability and curving performance. The analysis showed that the two modelling approaches gave comparable results with good agreement vertically. However, the study has highlighted that the representation of plan view behaviour of the models differed, particularly for stability.

A comparison of two models of vertical dynamic vehicle–track interaction in a transition zone between a ballasted track and a 3MB slab track is presented. The dynamic analysis is performed using 2D and 3D models in MATLAB and ANSYS, respectively. The Kelvin-Voigt model representing the foundation for the sleeper in the 2D model is calibrated based on the calculated track receptance from the more extensive 3D model, which includes the track superstructure on a layered soil foundation. Both models are used to simulate the passage of an iron ore freight vehicle through the transition zone at 60 km/h. Sleeper vertical displacements, sleeper–ballast contact forces and wheel–rail contact forces are compared. Both models show results for similar orders of magnitude. The simulation time is about 25 times shorter for the 2D model.

For a suspended monorail, the pendulum oscillation around the longitudinal axis of the vehicle is investigated to verify clearance. The pivot of the oscillation is formed by wheels with two flanges running on a steel rail. The main excitation is from the track alignment and can overlap to form inadmissible pendulum angles.

Railway wheels negotiating a crossing are known to generate a dynamic impact load while transferring from the wing rail to the nose and vice versa. Dynamic impact loads have been studied in the 70s in the UK and the so called P2 analytical formula derived against site measurement for the case of rail joint. The same formula has then been adapted to the case of crossing and used in the UK to analyze crossing performance against foot fatigue resistance. However, the original formula has not been thoroughly verified for the case of crossings and it is found to differ from the more detailed MBS based prediction. The work presented here is reviewing the original work by Jenkins from which the P2 formula originates and establishes how it compares with respect to a number of more advanced options to simulated wheels unsprung mass in the presence of a rail dip angle (rail joint or crossing) to advise on future revision of the formula better adapted to the case of crossing. Overall it is shown that most numerical models are providing consistent results but that the Jenkins formula is over estimating the loads, especially above 200 km/h and as the quantity speed times dip angle increase. Track models based on beam with discrete support provide more accurate prediction of detailed interaction with passing loads, that other simplified co-running track models cannot.

Vibrations resulting from dynamic vehicle-track interactions (VTI) offer valuable insights into track conditions. This paper presents an approach for track condition monitoring by detecting and quantifying multiple track degradations using a digital twin of the VTI system. Unlike existing techniques that focus on a specific degradation type at a single track component, our proposed method provides a generic and integrated framework. By combining a physics-based VTI model with a data-driven model, we dynamically update the digital twin’s state based on measured axle-box accelerations (ABA). We introduce a local ABA feature extracted from its spectrogram and demonstrate its effectiveness in distinguishing various degradations at different track positions. The implementation and capability of the proposed approach were demonstrated in a case study conducted on a transition zone of a railway bridge. The simultaneous track stiffness variations in the railpad/fastening and ballast layers were successfully detected, confirming the effectiveness of our approach. The case study also showcases the generality, interpretability, efficiency, and robustness of the proposed approach in identifying concurrent degradation. Our proposed framework opens new possibilities for cost-effective continuous track monitoring for railway infrastructure management.

This work applies numerical simulations and a drive cycle perspective for the estimation of wear on rail vehicle collector strips using an existing heuristic wear model. As it is crucial to understand the origin of wear patterns to ensure long service life, the proposed analysis method allows to identify the contribution of each drive stage during operation to the wear pattern and to compare their wear rates against each other. Input data is created by numerically simulating the power intake of a rail vehicle during a drive cycle between two stations and extracting power-speed couples for characteristic drive stages. The dynamic interaction between pantograph and catenary is then simulated using a FE-representation of the catenary and a pantograph model with two individually suspended flexible collector strips. Using these transient time signals as input data to the heuristic wear model, the lateral wear distribution along both collector strips can be estimated for each drive stage. Here, a representative run of a Swedish X2 higher speed train is used as a case example. The results show that mechanical wear dominates on average, but that there is a considerable electrical wear intensity, especially during acceleration. This contribution is however relativised by the short distance covered in this stage, and the total wear pattern is dictated by the cruising stage. The wear patterns show high dependence on the evaluated frequency range in the force signal.

The aim of this investigation was to study the feasibility of a novel nonlinear magnetic shock absorber in road vehicle applications. This shock absorber consists of an array of identical permanent repelling magnets with surrounding electromagnetic coils as a source of energy dissipation. The magnetic shock absorber was implemented in a quarter car model and its nonlinear dynamics were developed analytically. The developed model was implemented in a simulation environment and the results were validated using a quarter car experimental setup. The ride quality and performance of the novel magnetic shock absorber were evaluated and also compared to a conventional linear one utilizing the ISO 2631 standard. In response to a continuous rough road surface, the performance of the magnetic shock absorber was shown to be similar to the linear one. Further, the road holding capabilities were demonstrated to be superior in the case of the former. As an additional advantage, the magnetic shock absorber could be utilized to harvest the kinetic mechanical energy of the vertical response. The proposed concept can also be used in developing an active suspension through energization of the coils.

In the Shift2Rail project Pivot2 an innovative two-axle single suspension step metro vehicle is proposed. The single suspension step requires active suspensions to improve passenger ride comfort both in vertical and lateral direction. Two control approaches are developed, modal and blended control. Despite the good achievements with regard to comfort improvement, the robustness and performance of the developed controllers in relation to wheel degradation due to wear is unknown. Two different track types and three rail inclinations are used to generate worn wheel profiles with the KTH wear method creating a 75 wheel-rail combination set. For each combination, the comfort is evaluated with the vehicle travelling at constant speed from 50 km/h to 120 km/h with 5 km/h interval, producing a set of 1125 ride comfort evaluation points. Results show that both controllers are robust and that good ride comfort of the innovative vehicle can be maintained according to the EN12299 standard also in case of wheel degradation due to wear. Blended control produces enhanced performance with respect to its modal counterpart in vertical direction.

Modelling and reducing wear resulting from wheel-rail interaction constitute fundamental aspects in the railway field, primarily associated with ensuring running stability and safety while reducing maintenance interventions and costs. The main focus of this study is to conduct a comprehensive investigation into the development of a stable wheel profile that effectively reduces wear and essentially maintains its initial shape throughout the operation of the vehicle. The primary objective is to enhance the vehicle’s dynamic performance, improve ride comfort for passengers, and ultimately reduce maintenance costs. In addition to these goals, the study also aims at examining the wear depth associated with the proposed wheel profile and analyse its impact on the vehicle’s dynamic behaviour.

Rail corrugation is among the main issues related to urban railway lines and appears as a quasi-periodic irregularity on the running surface on the rail. A vehicle running on corrugated rails may generate ground-borne vibrations that propagate to buildings in the proximity of the railway line with possible complaints from the inhabitants. For this reason, a mathematical model for the prediction of preferential wavelengths of corrugation formation is a useful tool to support both the design of railway lines and infrastructure managers when the system is in operation. It permits to identify the root causes of the phenomenon and the effectiveness of potential mitigation actions. To this aim, a wheel-rail interaction model is formulated in the frequency domain. It is used to study the phenomenon on a sharp curve of a subway network, where corrugation appears on the low rail. In this paper, the effect of the tangential wheel-rail contact model on the evaluation of corrugation wavelengths is investigated. As a general comment, the wheel-rail interaction model is able to correctly predict the corrugation formation on the low rail and its wavelength, regardless of the considered force-creepage theory.

The sliding contact between the pantograph-catenary interface should remain uninterrupted to ensure the supply of electric power to railway vehicles. The resulting contact forces must also be within tight tolerances to avoid inducing damage on the assets and keep acceptable wear rates. The employment of advanced numerical analysis tools enables to understand better the pantograph-catenary interaction behaviour, supporting the design, development and de-risk the implementation of current collection systems. A challenging aspect to consider in these analyses is the contact wire height variation, e.g., found in level crossings and overbridges, and the associated vertical gradients that can impose train speed restrictions. To reach higher wire heights at level crossings, the pantograph has to extend from the train and its aerodynamic loads change, influencing the pantograph uplift forces. In this work a 3D multibody pantograph model is built and validated with experimental results. The aim is to analyse its interaction with a catenary with one level crossing and one overbridge. The aerodynamic drag and uplift forces applied on the pantograph components as function of its extension are computed in realistic operation scenarios using Computational Fluid Dynamics (CFD) approaches.

The high-speed and intensive operation of rail vehicles may lead to new issues of high-speed collisions, which become vital to operational safety. This study analyzes high-speed train collision problems. Firstly, a wide-velocity domain collision dynamics model is established, including a three-dimensional vehicle model with 38 degrees of freedom and a fixed track model with three layers of vibration; the mathematical model characterized the non-linear factors as wheel-rail contact, front-rear contact, and coupler overload behavior are established. Then, the train collision state mark (TCSM) is proposed, which can quantitatively evaluate the safety under different collision conditions. Finally, the influences of the initial attitude and the parameters of the absorber on the collision are studied. The results show that the initial vertical height difference and nodding angle will significantly increase TCSM. TCSM will first increase and then decrease with the increase of the force level of the absorber of the leading vehicle.

The OOR (out-of-roundness) wheel is one of the main excitation sources causing vehicle vibration. However, the OOR wheel is random, which indicates that the vehicle vibration obtained with a deterministic OOR wheel cannot comprehensively express dynamic performances. To this end, a probability analysis framework is proposed in this paper. First, the probability model of the OOR wheel is derived; Second, the equation of the vehicle system dynamics is modelled; Then, the direct probability integral method is developed to obtain the PDF (probability density function) of vehicle random vibration; Finally, the statistics characterized random vibration characteristics of the vehicle are calculated. The effectiveness of the proposed framework is verified with a case study. The results show that the PDF of vehicle random vibration excited by the Gaussian distribution OOR wheel excitation exhibits a right-skew shape, which significantly affects the dynamic performance. Compared to the Monte Carlo simulation, the proposed framework has higher computational efficiency for the same accuracy to analyze vehicle random vibration.

A method of collaborative simulation of the train collision process using a rigid motion model and a flexible collision model is proposed to solve the problem of the low computational efficiency of the finite element numerical simulation of the train collision process. This study investigated the collision response of a train derailment hitting a platform with different curve radii based on an accident in which a subway train derailed and hit a platform. Based on the results, a collision damage index is proposed to assess the relative degree of damage of train derailment collisions at different curve radii. The results reveal that within a certain radius of the curve (when the impact distance D exists), there is a positive correlation between the curve radius and the collision damage index, and when the curve radius exceeds a certain value (when the impact distance D does not exist), the train and platform do not collide.

The modernization of the rolling stock of the Paris metro and line B of the RER has led the infrastructure manager to attempt to predict the evolution of maintenance costs, with the help of MBS simulation (available at the tender phase). This approach relies on the correlation of corrective maintenance costs with the contact forces calculated by MBS over a known network. Ten parameters damaging function is defined consistent with steel fatigue evaluation method. Those parameters are adjusted by optimizing the correlation coefficient between the damaging function and the associated maintenance cost. In other words, the maintenance costs are modelled as a function of wheel-rail contact forces along the track. The method appears to work on an overloaded section of track, at least for the rail renewal maintenance activity. Tamping and reprofiling maintenance activity forecast produce mixed results. It is proposed to extend this method to the least loaded section of track as metro lines.

As an important part of high-speed train health management, the ability of axle box bearing fault diagnosis technology in multi-task has been focused by researchers in recent years. At present, multi-task fault diagnosis methods based on deep learning are normally limited by data conditions, and many algorithm models training only rely on basic bench laboratory data. Moreover, the multi-task information representation ability of the model is limited. To solve these challenges, a multi-scale fault diagnosis model for multi-task is proposed. The model adopts dynamic simulation vibration signal data which simulates real vehicle operation to fully train multi-scale deep learning fault diagnosis model based on CNN architecture, and effectively diagnoses axle box bearing faults from two perspectives of fault degree and fault location. The experimental results show that this method performs well in multi-task diagnosis of axle box bearing fault.

Rail fatigue damage and wear have a major financial and safety impact on rail-roads. Since 2017, the authors have created and shared a number of highly-detailed rail loading environments aimed at testing and calibrating rolling contact fatigue damage models and wear models. Creating these loading environments involves the collection of real-world data – track geometry, car types, car dimensions, truck suspension characteristics, car weights, train speeds, friction conditions, wheel and rail transversal profiles, rail surface hardness, rail crack depth, tonnage since last grinding, and rail surface photographs – repeated at each site several times over several months. Contact conditions are then computed using a large number of dynamic simulations with stochastically-selected inputs to best represent the actual traffic going through each site. Simulation outputs include contact patch characteristics – centre of contact, forces, creepages, traction forces and contact patch geometry – as well as the position of the car body, trucks, and axles relative to the track. The authors use pummeling analyses to validate the results of these simulations by comparison with existing rail surface conditions. With each iteration, the number and variety of test sites increases and the methodology evolves and provides more detailed datasets.

Active wheelset steering has been studied and implemented to improve the curving performance and stability of the wheelsets to overcome the drawbacks of the passive system. A control system for active wheelset steering must be robust to parameter variations and disturbances. A robust sliding mode controller with integral action (SMC + I) for active wheelset steering is therefore proposed and implemented in this paper to control wheelset lateral displacements to achieve perfect rolling conditions during curve negotiation. The robustness of the controller is achieved by deriving the control inputs bounded with known uncertain parameters. The control input is derived as a combination of the equivalent term and a switching term to reduce the amplitude of the switching input. A saturation function is used instead of a sign function in the switching term to provide continuous control. The integral action (I) is added to the sliding surface function to minimize the zero steady-state error. Co-simulation is executed to evaluate the performance and robustness of the designed controller. A conventional railway vehicle with two two-axle bogies with a maximum operating speed of 250 km/h is modelled in SIMPACK®, while the SMC + I controller is implemented in MATLAB/Simulink® for co-simulation. Two hydraulic servo actuators (HSAs), modelled with Simscape hydraulic libraries, are implemented in the longitudinal direction to steer each wheelset. The proposed controller ensures stability, finite-time convergence and zero steady-state errors for all possible running scenarios. This indicates robust performance of the designed SMC + I controller.

The modelling of railway rolling noise requires that wheel/rail interaction is considered in a frequency range up to some kilohertz and therefore involves the consideration of non-steady effects. In this context, the effect of non-Hertzian contact conditions and non-zero mean value of creepages have been seldom investigated. To consider these effects, an exact non-Hertzian non-steady state linear tangential contact theory has been implemented in the frequency domain and applied to the study of a metro vehicle negotiating a short-radius curve. The results of the implemented model are presented in the form of a comparative analysis in terms of the wheel/rail contact force, relative velocity, and the equivalent power radiation of the wheel to other existing contact theories including Groß-Thebing’s non-steady state theory, and a steady-state method based on Kalker’s Linear Theory with zero mean creepages. The comparison highlights differences between the models (either in the low or high-frequency range) which suggests that this exact non-Hertzian non-steady state linear theory is a promising tool for this study since it overcomes some of the limitations of the other models.

The Universal Cost Model (UCM) is a comparison framework originally developed in the EU S2R project Roll2Rail, that accounts for all aspects of running gear innovations that influence the whole railway system's Life Cycle Costs. It is a simulation-based framework enabling the comparison of a reference vehicle against an innovative one, showcasing the differential costs and benefits of said innovation. In the recently completed EU project NEXTGEAR, the UCM 2.0 was re-developed to address shortcomings of the original version, in particular the user friendliness but also refining some the theoretical foundation in aspects of wheel and rail wear, ballast damage and track settlement. One key aspect, not present in the original version and developed from scratch in UCM 2.0 was the addition of a switches and crossings (S&C) metal parts calculation to the infrastructure module, otherwise focused on plain line ballast settlement and rail degradation through wear and RCF. This paper describes the modelling work done to show how the driving forces on track damage were derived from a number of representative cases to achieve a simpler calculation process for the user. This enables the UCM 2.0 user to carry out the calculation without the need for access to detailed expert knowledge on S&C simulation.

The evolution rule of modal parameters of rail vehicle system is closely related to the vibration response characteristics, and thus affects the vehicle running quality. Frequency veering is a typical phenomenon in the evolution of system modal parameters. Based on fuzzy clustering and vehicle system dynamics model, the frequency veering research in the process of vehicle system modal evolution under speed change is carried out, and the relationship between vehicle system frequency veering and vehicle response characteristics is further explored. The results show that the combination of dynamic model and fuzzy clustering method can clearly track the evolution of vehicle system modal frequency and damping ratio; With the increase of running speed, the frequency veering occurs between the hunting modal frequency of bogies and the modal frequency of rigid car body, and the modal damping ratio changes significantly; The vibration response corresponding to the two modes with frequency veering is significantly increased. Moreover, at the speeds corresponding to the frequency veering, the vibration amplitude of the car body increases, and the vehicle running quality deteriorates significantly.

This paper focuses on rail corrugation, specifically on roaring rails and possible solutions to mitigate their impact. Rail corrugation is especially present in metro lines, due to the constant speed, direction and type of vehicles. The current standard solution to reduce the consequences of rail corrugation is to grind or mill the rails more frequently. This requires track closures, leading to shorter operating windows. We suggest the possibility of using different vehicle speeds as proposed in other papers to reduce the harmonic load part on the rail, and therefore reduce the effects of corrugation. To validate this statement, we performed measurements of vertical loads and rail stresses in a metro line in Vienna, recording both the existing rail corrugation and the reaction of the track to trains passing at these locations with various speeds. The results indicate a general reduction in the peak-to-peak values of both rail foot strain and vertical load at lower speeds. Interestingly, there is no clear influence of corrugation depth at higher vehicle speeds.

In driving bogies of railway vehicles, motors and driving devices are often arranged not in left‐right symmetry, but in point symmetry. In such cases, roll motion of the bogie frame tends to occur when the motors are driven and result in wheel load imbalance. However, few studies have focused on this roll motion of the bogie frame. In this study, the effect of the roll motion of the bogie frame on the wheel load imbalance on the left and right is examined, using parallel Cardan driving bogies as the subject. A one-vehicle model with parallel Cardan driving bogies is constructed using multibody dynamics. The simulation results show that the roll motion of the bogie frames causes lateral displacement of the car body. This lateral displacement causes an imbalance in wheel loads on the left and right sides of the wheelsets. It is found that this phenomenon also occurs under conditions where wheel slips occur and the re-adhesion control is in operation.

The onboard monitoring of the wheel-rail forces of heavy-haul freight cars is critical to the derailment evaluation due to in-train stability issues. In this paper, a wheel-rail force indirect measurement method is proposed based on the transfer characteristics of wheel-rail force and strain testing technology. Experimental and simulation results show that this wheel-rail force indirect test method has high identification accuracy, greatly reduces the test cost and the method is suitable for long-term safety monitoring of long and heavy load freight train.

In this study, a distribution and fault-tolerance control strategy, based on overdrive characteristics, were proposed for active steering bogie. Two control layer was utilized in this strategy. Initially, the traditional geometric control (GC) strategy was utilized, facilitating the acquisition of the target wheelsets’ yaw angle in the control layer. Subsequently, under brake conditions or actuator failure, the actuator's displacements were redistributed within the distribution layer. The results demonstrated that the proposed control strategy could facilitate coordinate control with either traction or brake conditions, thereby enhancing steering efficiency. Furthermore, in the event of a failure, it was found that this strategy could ensure the bogie's running safety.

Equivalent conicity (EC) in-service has been required in TSI INF and TSI LOC & PAS for several years. However, due to implementation difficulties, only a few infrastructure managers and railway undertakings currently include EC requirements in their maintenance programmes. A novel method called the Gradient Index Profile (GIP), which combines gradient index for wheel (GIPw) and gradient index for rail (GIPr), has been developed to complement and support EC. In this study, based on a large number of on-track measured rail profiles, we investigate the distribution functions of GIPr on tangent tracks. We also examine the correlations of GIPr with track EC with the nominal S1002 wheel profile (EC S1002) and in-service EC with a reference worn wheel profile (EC ref. worn), respectively. Finally, we propose maintenance limit values for GIPr, which should be useful for rail surface management related to vehicle running stability.

The hunting frequency is an inherent characteristic parameter in the wheel-rail system and can affect the modal behavior of the vehicle system due to its continuous variation with running speeds, which in turn dominates some structural resonance related-dynamics. This study focuses on the variation mechanism of the hunting frequency in the railway wheelset system. The variables in the wheelset system are controlled to study their effects on hunting frequency variation under speed parametric excitation. The dynamical hunting frequency is always lower than the kinematical hunting frequency due to the drag effect of the inertia forces. The saturation mechanism of hunting frequency is revealed and the limit value is analytically expressed. The effects of nonlinearities, including the wheel flange force and the creep forces, on the fundamental hunting frequency and the high-order harmonic frequencies are investigated. The results indicate that the nonlinearities should be considered for the precise calculation of hunting frequency.

With the increasing speed of high-speed trains, the wear of wheel and rail is becoming increasingly serious. It is difficult to take into account the contradiction between high-speed stability and curve negotiation capability of vehicles and the emerging new contradiction by setting conventional yaw dampers with fixed parameters. In order to further improve the comfort and high-speed stability of passenger trains and reduce the wear of wheel and rail, it is necessary to design a semi-active yaw damper solution. In this paper, an innovative design prototype of semi-active yaw damper is proposed and its numerical simulation model is established. The accuracy of the model is verified by bench test. From the perspective of dynamics, a control strategy of the yaw damper is proposed based on a real-time curve identification strategy. In order to verify the effectiveness of the implementation of the solution in solving the above problems at the same time, three different comparative operating conditions are designed through the roller rig and the numerical simulation model.

Design loads are important requirements for the development of safe rail vehicle bogies. Nowadays, design loads are determined using multibody simulations (MBS). Due to limited simulation capacities, it is important to reduce the simulation effort as much as possible. Therefore, representative scenarios can be used. These scenarios consider the horizontal track layout, driving conditions and track irregularities. However, vertical track layout is not taken into account. In this paper, the existing method of using representative scenarios is extended by representative vertical scenarios. To this end, vertical track layout is identified using measurements. Based on this identification, the most important parameters of the vertical track layout are identified. With these parameters, a statistical distribution is created. The representative vertical scenarios represent this distribution and therefore the vertical track. After the extension, the representative scenarios contain every important parameter for design loads. The representative scenarios are simulated and the results are compared with reference simulations.

Wheel-rail corrugated wear is composed of two main phenomena: wheel polygonization and rail corrugation. The interaction forces between the wheel and rail increase as a result of corrugated wear, which leads to fatigue damage in the track and vehicle components. Different types of vehicles excite various modes, such as the P1 and P2 forces of the rail, as well as the third-order modes of the rail between wheelsets. A combination of experimental and numerical simulation methods was used to investigate the initial formation of wheel-rail corrugated wear. Then a dynamic model representing the coupling between a high speed train vehicle and rail, as well as a wear model based on Mather’s period jump theory, were established for the formation of corrugated wear. The wear process is utilized to further elucidate its formation mechanism.

A pantograph and catenary model considering the overlap is established to study the influence of the height of crossing point of overlap on the dynamic characteristics of pantograph and catenary. The overlap is optimized by reducing the height of crossing point of overlap from 40 mm to 20 mm. The dynamic response between the pantograph and the catenary was calculated when the pantograph passes through two types of overlap at different operating speeds. The ANSYS modal solution method was used to solve the natural frequencies of the catenary at the first 50th order before and after the optimization of the overlap. The results show that reducing the height of crossing point provides a new solution for reducing the dynamic uplift of the contact wire and contact force between pantograph and catenary to a certain extent. In addition, the change in the height of crossing point of overlap affects the vibration characteristics of the catenary, further affecting the dynamic interaction relationship between the pantograph and the catenary, which is also reflected in the frequency domain response of contact force and uplift.

Rail corrugation is a typical rail cyclical disease which often occurs on heavy haul, urban transit, and high-speed railways. Rail corrugation has a significant impact on vehicle dynamic performance, especially on the axle box acceleration. It may cause the bolts of axle box to loosen or break the rail fastener, and even affect the operation of vehicle. Therefore, it is necessary to discover rail corrugation in time and to repair it by rail grinding, which is an important way to improve the safety of the vehicle. A numerical analysis method based on adaptive time-frequency feature extraction is proposed in this paper. First, acceleration sensors are installed on both the left and right side of the axle box. Then the vibration features of the axle box are extracted according to the line mileage segmentation based on the adaptive time-frequency feature extraction method proposed in this paper. Finally, the impact of different wavelength and different section length of rail corrugation is compared using field test data. The test results show that the method proposed in this paper can accurately extract the features of different wavelength and different section length of rail corrugation. Moreover, compared with traditional methods, this method is proven to be strongly adaptive and highly accurate.

Railway switches play a crucial role in ensuring smooth railway operations. Efforts to enhance switch safety standards led to the implementation of so-called TKK sensors in Sweden. These monitor the gap between switch rail and stock rail as a complement to the switch and locking devices. However, these devices are susceptible to faults, leading to increased maintenance and operational expenses. This study was therefore initiated to assess the utility of these devices in derailment prevention. To assess the risk of derailment caused by foreign objects getting stuck between the switch and stock rail, multibody simulation (MBS) evaluations are performed. A structural track model is built where the switch panel and adjacent track is modelled using Simpack’s non-linear flextrack module. Results from the simulation indicate that the train will not derail when the foreign object is modelled with a failure criterion resembling crushing of ballast stones. Consequently, the inclusion of additional TKK devices does not significantly improve the intended safety levels for the investigated simulation cases. Further investigations into ballast stone properties, different switch designs and traffic situations are needed to draw firm conclusions.

This paper presents a finite element model of a railway crossing panel for use in multibody simulations (MBS). It is a two-layer track model with rails and sleepers represented by beam elements, and a crossing rail represented by three-dimensional (3D) solid elements. The track model uses linear bushings for rail fastenings and bi–linear bushings for ballast to allow for potential voids between sleepers and ballast. The model is calibrated and validated to measurement data from a comprehensively instrumented switch & crossing (S&C) demonstrator installed in the Austrian railway network as a part of the European research programme Shift2Rail. A parameterisation with eight parameters relating to track stiffness and ballast voids is introduced to enable the calibration. In a comparison it is shown that the 3D model and a more conventional beam model of the crossing show similar levels of agreement against the measurement data. The 3D model has an increased computational time of about 25% compared to the beam model.

In order to realize low-cost track maintenance for regional railway lines, the authors successfully developed the track management system based on the car body vibration data, which are measured on commercial passenger trains by a smartphone with MEMS and GPS velocity meter. After the compensations using numerical filtering of GPS velocity and the waveform-matching between the “car body vibration fluctuation” and the “track longitudinal level irregularity change”, the reproducibility and the accuracy of track position are increased and the measured data become reliable enough for track maintenance. According to the analysis on collected huge data for more than 3 years, the relationship of the train vertical vibration vs. the track longitudinal level irregularity has good positive correlation, so, the track condition can be expected from daily train vibration monitoring. As a result of these studies, the authors propose a new economic track management approach.

High-speed turnouts are the key components of high-speed railways. The crossing panel in the turnout is one of the critical zones where high loads occur when the train passes through. To reduce the dynamic forces during high speed or heavy haul trains passing, swing nose crossing designs are used. For those swing nose crossings, a drive and locking unit is used for positioning the crossing nose for the correct driving direction and to keep the crossing nose safely in position. To guarantee the correct position a detection unit is integrated into such a drive and lock unit. The focus of this paper is on the numerical simulation of the detailed swing-nose crossing together with drive locking and detection (DLD) devices and their behavior during high-speed operation. For this purpose, a dynamic model based on the Finite Element Method (FEM) is presented that enables to investigate the deflections and stresses in the turnout components as well as the dynamic behavior of the DLD system and its influence on other components during wheel passage.

In the last years, railway research for good transportation is mainly focusing on the reduction of emissions and costs and for this reason the possibility to increase the length and the hauled mass of freight trains is studied. Since the running safety and train integrity must be always guaranteed, the control of both traction and braking phases becomes crucial. In fact, considering all the possible scenarios, sufficient power and promptness of tractive and braking actions must be always ensured.This paper investigates how the longitudinal compressive forces (LCF) are affected by the positioning of additional locomotives and wagons along the train. A simplified trainset model is used in order to estimate the maximum buffer forces during emergency braking of a set of 500 trains generated with random payload distribution. An optimisation algorithm developed for combinatorial problems is used to change the payload sequence and the position of the slave locomotive on each train, in order to minimize the buffer forces. The optimized train sequences are then analysed with a more accurate model for longitudinal trainset dynamics showing that a proper positioning of wagons and slave locos can reduce buffer forces by more than 40%.

Low adhesion conditions have a significant effect on the operation of rail networks. Each Autumn in the UK, leaf fall timetables are introduced, adjusting timings so that drivers can adopt more defensive driving techniques. A rail system’s situational awareness would be greatly increased if each train could report the adhesion conditions for the track over which it had just passed, allowing optimised operation of both service trains and rail head treatment trains.The testing presented here was commissioned to provide data for the development of an on-train Low Adhesion estimation system that can estimate the adhesion conditions beneath a rail vehicle in near real-time. This paper describes the instrumentation and testing of a full-scale vehicle over a section of track with artificially lowered adhesion conditions. The dynamic properties of the vehicle are shown to change with adhesion level.

This work presents an analysis of the sensitivity and impact of various vehicle parameters on the estimation of ballast settlement cost in passenger and freight systems in the Universal Cost Model (UCM). The study compares the vertical force obtained from multibody simulation results to analytical solutions for passenger and freight wagons. These results highlight the significance of considering unsprung mass, vehicle type, and vertical suspension parameters when estimating ballast settlement cost with the analytical representation of the $${P}_{2}$$ P 2 force. For passenger vehicles, the simulated $${P}_{2}$$ P 2 force is sensitive to all investigated parameters, with an average sensitivity of approximately 18%. The choice of method for determining vertical force for simulated track irregularities also influences the impact of these parameters. The simulated $${P}_{2}$$ P 2 force for the track section with track irregularities exhibits a higher percentile difference compared to other track cases, indicating that the parameters have a greater impact on the simulation of $${P}_{2}$$ P 2 force. In contrast, for freight vehicles, the simulated $${P}_{2}$$ P 2 force shows sensitivity only to two out of seven investigated parameters: the vertical stiffness of the outer and inner coil springs. The impact of these parameters is dependent on track irregularities and the chosen method for determining vertical force. The standard deviation measure has the highest impact on the outer coil spring, while the 99-percentile and mean value measure show a medium and minimal impact, respectively. The inner coil spring has an overall minimal impact across all track cases and comparison methods. These results show that the existing UCM methods can be improved by incorporating the identified parameters, thereby enhancing the accuracy of ballast maintenance cost estimation modules.

Due to the inevitable wheel polygonal wear in operation and the increasing running speed, the service operation environment severely challenges the safety and reliability of gear transmission bearings. To investigate the dynamic responses of bearings excited by wheel-polygonal wear, a vehicle–track coupled dynamics model with gear transmission systems and its bearings is developed. In this model, the nonlinear factors, such as gear mesh stiffness, gear backlash, bearing nonlinear contact, and frictions between bearing roller and raceways, are comprehensively considered. This model has the advantages of analyzing the dynamic behaviours of gear transmission system and evaluating the dynamic responses of the bearings in the coupled mechanical systems. The model is validated by the field test data, and the wheel polygonal wear data is also obtained by field test. Using the dynamics model, the influence of wheel polygonal wear on the dynamic responses of gear transmission bearing in traction condition is analysed and discussed. It indicates that the wheel polygonal wear increases the dynamic interactions within all bearings, and can’ be ignored in the dynamic related research.

This paper studies the control of independently rotating wheels (IRWs) in railway vehicles with the use of magnetorheological dampers. The development of a semi-active strategy for steering/guidance control is presented. A conventional bogie vehicle with IRWs is then used in the study to carry out a comprehensive performance evaluation in comparison with a full active control. The study demonstrates that the proposed semi active control system is effective in providing the wheelsets with the necessary steering on curves and self-centring ability on straight track with irregularities.

Short pitch corrugation is a typical defect on rail surfaces that induces high level of noise and increases maintenance costs. Despite numerous research efforts, corrugation development mechanism has not yet been fully understood and root-cause solutions have not been developed. This work numerally simulates the rail corrugation in the V-Track test rig, aiming to better understand corrugation mechanism and also link the scaled laboratory tests to the full-scale reality. A three-dimensional finite element model of the V-Track is established to simulate the vehicle-track dynamic interaction. The fastening and ballast parameters are calibrated by fitting the simulated track receptances to hammer tests. Rail corrugation with a major wavelength of 5.7 mm is successfully reproduced using the FE model, which shares features similar to the experimentally produced corrugation in the V-Track. The numerical simulation demonstrates that a rail longitudinal compression mode at 790 Hz is the ‘wavelength-fixing’ mechanism of corrugation in the V-Track, agreeing with the experimental results. This work numerically verifies the dominance of the rail longitudinal vibration modes on corrugation formation.

Although railway transportation is generally considered safe, derailments still occur causing significant service disruptions and economic losses. Therefore, reducing the number of train derailments is crucial for improving railway transportation safety. This paper presents a derailment detection system for freight trains that has been designed and tested based on full-scale freight wagon derailment tests performed in a previous experimental campaign. The system uses an algorithm that processes and analyzes data to identify the freight wagon derailment condition. A LoRa-based wireless communication system has also been implemented to send the freight wagon derailment warning to the locomotive. A freight wagon has then been equipped with the proposed derailment detection system, which has proven more robust against false triggering than the mechanic-pneumatic derailment detector based on the crossing of a single threshold. Furthermore, the proposed LoRa-based wireless communication system has proven to be effective for wagon-locomotive communication with different convoy compositions and freight wagon loading conditions.

Self-excited torsional vibrations in the wheelset axle may lead to undesired phenomena, such as passengers’ discomfort, wheel polygonization or press-fit instability. The main cause is a sudden adhesion change in the wheel-rail contact, which modifies the contact energy. Measurement data from three different vehicle types including more than 30,000 torsional vibration events were analyzed to develop a new transient creep force model. This model uses only a single degree of freedom, which is later related to a physical quantity, i.e., frictional power. It requires a low computational effort and allows a straightforward statistical analysis of the results. Herein, the model is applied to one full dataset. It provides a creep curve for each point in time. Thus, it reproduces all the contact energies and the wheel-rail adhesion coefficients during a transient adhesion cycle. The results show a good agreement to measured data. The developed model can be used to simulate the torsional vibrations, it provides a physical-based explanation of the involved phenomena occurring in the wheel-rail contact, reduces time and cost of the measurement campaigns, and improves the assessment of torsional vibration events in the design stage.

In this paper, an experimental investigation is carried out to assess the possible use of axle-box acceleration measurements to identify the presence of a transverse crack in railway axles, detecting components of axle vibration occurring at frequencies that are integer multiples of the axle’s frequency of revolution (N × Rev components). The experimentation was performed propagating the cracks of different dimensions induced into a pair of railway axles mounted on a freight wagon by means of full-scale roller rig tests. The results show that the 3 × Rev components of the horizontal axle-box acceleration is well correlated to the size of the crack and less sensitive to the effect of disturbances induced at the roller-wheel contact with respect to the vertical acceleration. Hence, they represent a promising possibility for the continuous monitoring of axle integrity. Specifically, the obtained experimental results suggest the possibility of detecting cracks with sizes larger than 11–12% of the axle section.

In recent years, condition monitoring technology has been actively developed aiming at more safer operation and maintenance cost reduction. In this study, condition monitoring device attached on trackside is used for the monitoring of railway bogies in terms of the diagonal wheel load imbalance ratio $$R_d$$ R d . In general, the ratio $$R_d$$ R d widely varies even though the same train pass on the trackside device. Therefore, the factors that cause the variation of $$R_d$$ R d should be investigated to improve the measurement accuracy. In this paper, the correction method to reduce the variation of $$R_d$$ R d is mentioned and is examined utilizing experimental data collected by roller-rig test stand. According to the analysis with collected data during service operation, it is confirmed that the proposed correction method is more effective than previous data processing method with trackside device in terms of estimating the value of diagonal wheel load imbalance ratio.

Excessive underground train-induced building vibration is an environmental concern resulting in human distress. Wheel polygon is probably one of the main vibration sources. In the present work, an explicit-integration time-domain, fully coupled 3D dynamic train-track-tunnel-soil-building FE model is developed and employed to investigate the effects of wheel polygon on the building vibration. Measured wheel polygon data is analyzed and input into the developed FE model. Based on the simulation results, it is found that the contribution of the wheel polygon to the building vibration is considerable in the frequency range from 30 to 180 Hz. Wheel polygon makes the building vibration more pronounced at the P2 resonance frequency and the passing frequencies (f = v/λ) of wheel polygon. From the foundation to a high floor in the building, the effect of the P2 resonance-related wheel polygon attenuates the slowest while the effects of the other orders of wheel polygon attenuate fast.

In this paper, two commonly used creep force algorithms in rail vehicle dynamics simulation, namely FASTSIM and Shen-Hedrick-Elkins, are extended to solve non-Hertzian wheel/rail contact problems based on the SDEC regularisation of non-Hertzian contact patches. The extended algorithms for non-Hertzian conditions have been implemented as user routines in Simpack which enables the assessment of the influence of the extended force models on the rail vehicle dynamics through comparison to the traditional Hertzian models in the same environment. To this end, a single wheelset and a complete rail vehicle model are selected as case studies to demonstrate the application of the developed non-Hertzian creep force models in rail vehicle dynamics simulations, and its impact is studied by comparative analysis of the simulation results obtained from using both Hertzian and non-Hertzian models. The results suggest that the Hertzian and non-Hertzian creep force models result in different dynamic behaviours of the system and the level of difference can be significant in a certain context which may cause different conclusions on the assessment of the system, for instance in view of vehicle homologation.

Wheelset rotational velocity variation in curved tracks causes measurement error of velocity, which leads to the error of the train location for the moving block system. Thus, clarifying the mechanism of rotational velocity variation is important to evaluate accuracy of the location detection for trains. To observe rotational velocity variation in a curved track, experiments and MBD simulations are conducted. The result of the experiments indicate that rotational velocity variation occurred, and the degree of variation of the front axle of the bogie is larger than the rear axle of the bogie. The result of the simulations shows the same tendency as the experiments, which suggests that the phenomenon of rotational velocity variation can be simulated. As the mechanism of rotational velocity variation, three factors are identified: rail length difference, variation of wheel rolling radius, and longitudinal creepage. To analyze the variation mechanism, a visualization method for the three factors is developed. The result of visualization suggests that the main reason for different variations between the front and the rear axle is the effect of different directions of longitudinal creepage.

A Digital Twin of a typical 4 car impact testing arrangement as per AAR M-921 or similar is set up to enable investigation of the performance of a dual draft gear as may be fitted in long pocket draft gears as detailed in USA Patent No. 10,086852 B2. Of interest is the combination of very different draft gears and the modelling and numerical problems that may be introduced to modelling with two complex and non-linear devices being modelled in series. The long pocket dual draft gear was fitted to the Hammer car (68.4 tonnes) whilst normal draft gears were fitted to the three Anvil cars (100 tonnes each). The 4-car system was modelled with eight masses using realistic masses for the coupler pairs (300 kg) and a separate mass (50 kg) for the follower that is used to separate the two draft gears in the long pocket in the Hammer car. The modelling approach allowed explicit mathematical models to be used for each individual draft gear and hence retaining of the response complexity in the simulated impact tests. Three very different draft gear types were simulated demonstrating the usefulness of the approach.

Building a digital twin for a train requires a real-time simulation model that accurately replicates the train's behaviour and performance under various operating conditions, enabling digital twin-based applications such as real-time control and monitoring, predictive maintenance, and the prediction of potential faults while testing coping strategies. To meet this requirement, we propose a physics engine-driven approach, employing a physics engine as a real-time simulation tool to model and simulate the dynamic behaviours of the train. We have modelled and simulated the vehicle derailment scenarios using the physics engine-driven method and the traditional multi-body (MB) model, respectively. Comparative analyses between the two types of models have been conducted to assess and validate the feasibility and usefulness of the proposed method. In addition, two application cases of the physics engine-driven method are also presented in the paper. The results demonstrate that while the physics engine-driven model exhibits relatively lower accuracy compared to the traditional MB model, it presents excellent real-time performance. This suggests that if future improvements in accuracy are achieved, such as integrating with the AI model, the newly proposed method could serve as a promising alternative for developing a digital twin train.

In this paper, a methodology to predict the track longitudinal level using bogie vertical acceleration from in-service vehicles is proposed. To account for the effect of vehicle speed, the acceleration levels are double integrated on-board the vehicle. Synthetic indicators like the RMS are then computed over predefined track sections of 100 m, to reduce the amount of data to be stored and analysed. Then, a linear regression model between the double integrated indicators and the direct track geometry measurements collected by a TRV is built, to verify the degree of correlation of the two quantities. To this end, data collected during a long-term monitoring campaign along the Italian railway network are considered. The regression model is finally adopted to predict the RMS of the longitudinal level using the signals collected on-board the vehicle. The comparison between the predicted and measured data is shown to be promising towards the possibility of condition monitoring of the track geometry both on high-speed and conventional lines.

Differential settlement in transition zones of railways tracks is a consequence of variable track stiffness and load distribution potentially leading to the development of voided sleepers. This paper addresses the simulation of differential settlement in transition zones of turnouts. An iterative settlement procedure (ISP) has recently been proposed which combines short-term simulations of the vehicle-track interaction with long-term assessments of the settlement. A finite element model is used in order to estimate the track sublayers stresses. Owing to the asymmetry of turnouts, this ISP is extended in order to consider non-symmetry. The symmetrical and non-symmetrical approaches are compared in the case study of the Shift2Rail demonstrator located near Vienna, Austria. The transition zone between the plain line and the switch panel is considered where a good calibration of the short-term model is obtained. Further works should study the influence of flexible sleepers, the level of discretization and the dynamic contribution of substructure stresses. The novel non-symmetrical approach should prove even more relevant in the transition zone between long and short bearers in the crossing panel. Long-term monitoring tests on the track settlement are recommended to verify the accuracy of the proposed settlement prediction model. It is hoped that the novel approach can be used to help design and/or validate innovative concepts of turnouts and their effects on train dynamics.

The structure of the railway catenary determines the current collection quality of the pantograph-catenary system. As the catenary is a tension structure with small damping, it takes several minutes to back to the static state once it vibrates. Due to the wave propagations, the contact wire starts to vibrate before a front pantograph reaches, and a rear pantograph faces a worse condition. To lighten the catenary’s earlier vibration, a damping-enhanced catenary structure with unidirectional rotary dampers is proposed. The unidirectional rotary dampers are adopted and installed on the supporting of the steady arms, making which to be undamped for the uplift process and damped for the falling process. The enhanced damping values can be acquired through experiments. The dynamics of the proposed structure are studied and compared with the traditional one. The results show that it’s an effective way to alleviate the catenary’s vibration and improve contact quality, especially for a rear pantograph, which may be promising for the 400 km/h or higher speed railway.

The fatigue reliability of railway bogies is significantly decreased due to the structural flexibility and wheel-rail interactions. The wheel-rail coupled vibrations, i.e. the P2 force, can be excited by rail welded joints or the wheel out-of-roundness. Besides, the dynamic vibration and stress of the bogie frame are of relevance to the track types. In this work, the field tests of the vehicle-track coupled system are introduced to make insight into the dynamic behavior of railway bogies due to wheel-rail coupled vibrations on stiff or elastic tracks. Furthermore, the vehicle-track rigid-flexible coupled dynamic model is developed and verified to reproduce high-frequency vibration and stress. The mechanism of the modal vibration induced by wheel-rail interactions is further studied. Finally, some parametric studies, i.e. train speed, modal frequency, track stiffness as well as wheel-rail defects, are conducted to propose possible solutions to this issue. To decrease the track stiffness or suppressing the wheel-rail roughness can relieve the wheel-rail coupled vibration. To change the train speed or modal frequency can avoid vibration-induced fatigue failure.

Modelling wheel-rail contact within multibody simulation environments usually requires additional libraries or methods for handling creepage. Although specialised software such as Vtech CMCC CONTACT.dll allows for a precise contact discretisation it is time consuming and therefore not applicable for real-time capable models required for hardware-in-the-loop. Therefore, this paper introduces a new method that facilitates a fast wheel-rail contact analysis in MATLAB® Simulink® without introducing co-simulation. The new approach allows for the use of recorded real wheel/rail surfaces from laser scans and enables real-time simulations carried out on a dedicated Real Time Target Machine (RTTM) from Speedgoat. This paper presents the wheel/rail profile description method with the optional use of real laser scans and compares it to a Simpack model in a benchmark. By meshing rail profiles as surfaces and describing wheelsets as a point cloud in Simulink® Simscape, it becomes possible to simulate a hydraulic-mechatronic active steering system with individually suspended single-driven wheels, integrated into a modified tram in Zurich.

As a passenger carrying component, the vibration level of railway vehicle carbody directly influences the ride comfort of passengers. For the vertical elastic vibration suppression of railway vehicle carbody, the traditional technology mainly focuses on the design of carbody modal frequency, the method of increasing damping and the design of dynamic vibration absorber, with little attention to the design of modal shape. So, a novel vibration suppression method based on the control of modal shape node is proposed in this paper, that is, by adjusting the weight distribution of carbody along the length direction to achieve the purpose of controlling the first-order vertical bending modal shape node positions, so that the nodes can be close to the carbody-bogie interface locations to reduce the modal generalized force, and then the carbody vertical elastic vibration is suppressed. The traditional carbody model with uniform cross-section Euler-Bernoulli beam is replaced by variable cross-section beam model, and the influence of the weight distribution on the modal frequency and modal shape node position of the carbody is studied. At last, the full-scale railway vehicle roller rig is used for the vibration suppression method verification. The theoretical analysis and experimental results show that: by reasonable designing the weight distribution of the carbody, the modal shape node position of first-order vertical bending mode can be controlled, and then combined with the bogie distance design, the vertical bending elastic vibration of the carbody can be suppressed effectively.