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For conformal contact situations, some of the assumptions employed in classical contact theories, such as the flatness of the contact area, lose their validity. Existing conformal contact models are challenged by either accuracy or computational efficiency. With the aim of achieving a balanced trade-off between these contrasting requirements, this paper proposes a new simplified method to solve conformal rolling contact problems, which is based on fast non-Hertzian contact model INFCON and FaStrip. Numerical experiments are performed for two typical wheel/rail conformal contact scenarios to assess the performance of the proposed method, taking as the reference the CONTACT method for conformal contacts. The comparative analyses show that the proposed method is in good agreement with the reference method in terms of the determination of the contact stresses, total forces, and the prediction of wear, whereas the traditional half-space approach fails to capture the main features of the conformal contacts. In addition, the high computational efficiency of the proposed method shows the potential for application in vehicle dynamic simulation and damage analysis. [ABSTRACT FROM AUTHOR]

Shimmy is one of the important factors affecting the ride comfort and lateral stability of straddle-type monorail vehicles with single-axle bogies (SMVS). To obtain the main parameters affecting SMVS shimmy, a global sensitivity analysis strategy for SMVS shimmy is proposed. The shimmy response surface model is constructed, and the sensitivity analysis of the shimmy response surface model is carried out by the Sobol method. Based on this, the shimmy factor model of SMVS is established by factor analysis method. A novel SMVS shimmy analysis method based on factor model is proposed. The shimmy factor model is verified by the dynamic model of SMVS. The results show that 11 main factors affecting the shimmy are obtained by sensitivity analysis. Through the dimension reduction technology of factor analysis, four main factors affecting SMVS shimmy are extracted. The complex coupling relationship between the shimmy factors of SMVS is revealed. The established shimmy factor model can effectively analyse the shimmy state of SMVS, and the dynamic simulation results also show consistency. This study not only proposes a new perspective to understand the SMVS shimmy mechanism, but also provides the foundation for further optimal design of monorail vehicle stability. [ABSTRACT FROM AUTHOR]

Couples of heavy-haul freight cars are simulated, using a 62-degree-of-freedom multi-body model developed on Simpack®, running on both tangent track and circular curve under different conditions. A benchmark simulation running at a speed of 70 km/h is set up, and then, different breaking scenarios with 2.5 kN, 5 kN, 7.5 kN and 10 kN of abnormal braking force application are simulated. In this paper, the effect of forces acting on the wheel–rail interface is compared using the derailment coefficient (L/V) and the material wear, defined by energy dissipation (Tγ). For the double-wagon setup placed in various positions along the train, the simulations run under no braking and abnormal braking conditions, where the braking force acts in only one of the wheels of the wheelset. This condition leads to an increase of up to 18% in L/V in one curve and up to 17% of reduction on the curve in the other direction. The wear increases 68% and decreases 71%, depending on the direction of the curve. These effects haven't been associated with longitudinal dynamic effects in previous studies, including in-car shocks and traction forces. [ABSTRACT FROM AUTHOR]

Wheel maintenance is a complex process whose costs can be reduced with good planning. One of the main difficulties is the prediction of a worn wheel profile shape on a train. With existing modelling approaches, it is possible to predict a worn wheel profile quickly and accurately for a unique operating situation. For varying operating scenarios, it is a more time-consuming process and often less accurate manner because so many, sometimes even unknown, input data are needed. With the new hybrid approach developed in this work, it is possible to combine the advantages of both approaches (fast, accurate, varying operating scenarios). The hybrid approach builds on historical data sets of two trains in combination with multi-body dynamic simulations. In these simulations, two different wear models have been used, one based on the maximum shear stress, the other on the wear number in the contact point. The wear model approach based on the maximum contact shear stress was confirmed as accurate through the application of the hybrid model and validation using real track measurements. This will help to improve the prediction of maintenance intervals and, thus, to reduce the costs. [ABSTRACT FROM AUTHOR]

A novel parameter identification method was proposed for vehicle suspensions subjected to performance degradation. The proposed method does not require the measurement of the stiffness and damping coefficients of suspensions. Instead, it uses vehicle states to calculate the stiffness and damping coefficients based on an efficient multibody model and inverse dynamics. First, a full-vehicle system was modelled using a semirecursive multibody formulation, and the dynamic properties of suspensions, chassis frame, and tires were considered. Second, dynamic simulations on a bumpy road were performed, and vehicle state data were collected. A deep neural network (DNN) model, whose inputs and outputs were vehicle states and suspension parameters, was developed. The DNN model can estimate the stiffness and damping coefficients based on vehicle states measured by sensor networks. The parameter identification was achieved by deep learning of the relationship between vehicle states and suspension parameters in a given maneuver. Finally, the model accuracy was investigated in terms of different DNN inputs, data samples, and hidden layers. The results showed that the DNN model predicts accurate stiffness and damping coefficients in real time. This maneuver-based parameter identification method can be used for the condition-based monitoring or fault diagnosis of vehicle suspensions subjected to performance degradation. [ABSTRACT FROM AUTHOR]

A Benchmark of railway multibody dynamics software application to switches and crossings (S&C) is presented, comparing all major commercially available software and a few independent codes. Two different representative S&C have been implemented, using the Manchester Benchmark passenger vehicle. The final results show that all software offer a reliable and efficient way to understand the kinematic and dynamics forces between the wheels and the track elements. The highest challenges are found when modelling a combination of multiple rails in simultaneous contact with a wheel (check-stock or switch-stock), large longitudinal variations in rail shape (crossings) and high lateral steering forces (diverging cases in tight radius). In those cases, the codes able to account for the exact relative motion of each wheels with respect to each rails independently are the most apt. The most significant variations between software are found in the contact prediction with an influence on the detailed contact tangential and normal forces. The user variability is found to be very small, with the most time-consuming and error prone being the task of handling the input data for the variable rails definition. All software could benefit from improvements to assist the user and ensure higher reliability and efficiency generally. [ABSTRACT FROM AUTHOR]

The design and maintenance of turnouts implies considering a great number of external factors that have an effect on their structural integrity. The proper generalised decomposition (PGD) method is used in this paper to carry out a parametrised study of the vehicle-track interaction in a non-intrusive way. The reduced model is built using a defined domain for some of the influence parameters: the vehicle speed, the wheel/rail friction coefficient and the axle load. A major assumption of the PGD solution is its ability to express quantities of interest in a separated form. One of the goals is to show the relevance of separability in the field of railway dynamics. The example of a switch is chosen as a validation of method. The output of the PGD model is the dissipated energy per metre in the switch rail. The robustness of the reduced model is verified using the complete solution. Probabilistic simulations are carried out in order to explore the possibility of using the PGD solution as a numerical abacus in dynamic simulations of switches and crossings. These first tests show that the PGD solution is a promising reduction model method in railway dynamics. [ABSTRACT FROM AUTHOR]

This paper compares different track model formulations for the simulation of dynamic vehicle–track interaction in switches and crossings (S&C, turnouts) in a multi-body simulation (MBS) environment. The investigations are an extension of the S&C simulation Benchmark with the addition of a finite element model of a 60E1-760-1:15 turnout. This model constitutes a common reference from which four different track formulations are derived: co-running, modal superposition, finite element incorporated into the MBS model and finite element coupled to MBS using a co-simulation approach. For the different track models, the difference in modelling technique, results, simulation time, and suitability for different simulation tasks is compared. A good agreement is found between the different track model formulations for wheel–rail contact forces and rail displacements. This study found a better agreement between co-running and structural track models compared to previous studies in the prediction of wheel–rail contact forces. This appears to be due to the increased complexity of co-running track model used in this study together with a tuning of the co-running track model to the reference model in a wider frequency range. For the reader interested to reproduce the results in this paper, the reference track model is available for download. [ABSTRACT FROM AUTHOR]

For the development of condition monitoring algorithms for turnouts, an extensive dataset consisting of measurement and simulation results is required. The basis for reliable simulation results are precise and easy applicable measurement techniques of the turnout geometry, like 3D handheld scanners. The challenge in using the data from portable 3D scanners for vehicle/track interaction simulation lies in the correct alignment and preparation of the measured surface. In this paper, a methodology for pre-processing of 3D scanner measurement results is presented, based on turnout measurements with the device HandySCAN 700 from Creaform. Point cloud processing methods like Principal Component Analysis and Iterative Closest Point algorithm are used to align the measured surface to a reference frame. Interpolation of the measured points by CAD reference data is applied for repairing the profile sections due to missing surface points. Furthermore, comparisons were made regarding the quality of simulation results for different input sources. It can be shown that the results have a good quality agreement in respect of different profile measurements techniques. Thus, it could be shown, that the data from the portable 3D scanner can be used for multibody dynamic simulation after appropriate preparation with the presented method. [ABSTRACT FROM AUTHOR]

This paper presents the final description for the S&C Benchmark that was launched at the IAVSD 2019 conference held in Gothenburg, Sweden and completed by eighteen participants by the end of 2020. The purpose of this paper is to allow for the replication of the Benchmark exercise after publication for those who wish to do so in the future, and it includes a link to the repository containing all necessary input data. The original task description, including a description of the Benchmark submission, is presented in full. The results from the Benchmark are available in [Bezin Y, Pålsson BA, Kik W, et al. Multibody simulation Benchmark for dynamic vehicle-track interaction in switches and crossings: results and method statements. Submitted to VSD, 2021]. [ABSTRACT FROM AUTHOR]

Railway vehicle dynamics is strongly affected by track irregularities, which can influence the safety and the running behaviour of the vehicle. The EN 13848-5:2017 standard provides the limits of track irregularities for standard track but does not states specific restrictions for switches and crossings. Furthermore, since turnouts have a limited length, their track geometric irregularities cannot be accurately described by stochastic functions usually adopted for railway vehicle dynamics simulations. Nevertheless, irregularities in railway turnouts, related to the non-uniform stiffness of the track support and to the variation of the rail profiles along the longitudinal direction should be considered in dynamic simulations, as they can generate large dynamic loads, strongly affecting the vehicle dynamics and running stability. The aim of the paper is to expand the Switches and Crossing benchmark exercise analysing the effect of several kinds of irregularity with different wavelengths and amplitudes on a complete turnout on the main quantities related to the vehicle dynamics. The influence of each defect on each quantity is estimated through a post-processing sensitivity analysis based on power spectral density calculation. This sensitivity analysis is hence used to combine different types of defects in order to detect irregularity combinations that could compromise running safety. [ABSTRACT FROM AUTHOR]

In this work, a four-link serial-chain mechanism which is an equivalent representation of railway wheelset is proposed. Through this representation, it has been shown that the concepts like instantaneous roll centre, dynamically varying link lengths, and shape constraints can be used to account for wheel–rail contact into the existing multibody formulation. An outline of the framework is described for dynamic analysis of a suspended wheelset model. It is possible to conveniently include kinematic non-linearities into the equations of motion. Usually, these terms are overlooked while using elastic approach for wheel–rail contact. Essentially, benefits of two conventionally followed approaches, namely, elastic, and constrained contact, are exploited in this work. Through a parametric study, it was found that such nonlinear terms have significant impact on hunting stability of wheelsets having high conicity. [ABSTRACT FROM AUTHOR]

Aiming at preventing frequently occurred coupler jack-knifing in slave control locomotives of 20,000-tonne heavy-haul trains, a theoretical and experimental research on enhancing the coupler stability has been carried out. Field tests are conducted to ascertain the load characteristics of the slave control locomotive, and the coupler stability mechanism of the locomotive is studied. A dynamic simulation model considering the locomotive, adjacent wagons, and attached coupling devices is established and validated. Based on the model, countermeasures for improving the coupler stability are studied. The field test results indicate that: 1) the slave control locomotives suffer from sustained compressive forces less than 1500kN at the braking stage of cycle braking, while the maximum short-term impact force at the release stage exceeds 2000kN; 2) The coupler jack-knifing mostly occurs at the braking stage, and the yaw angles of the middle couplers are larger than the front and rear couplers. According to the theoretical analysis and dynamic simulation results, the coupler stability can be improved by increasing the stiffness of secondary lateral bump stops and reducing its clearance. Moreover, the proposed countermeasure of setting up lateral bump stop to locomotive couplers is proved to be effective to prevent the coupler jack-knifing. [ABSTRACT FROM AUTHOR]

Turnouts are among the weakest links of railway lines, but the derailment risk of vehicles passing the through route of a turnout is seldom considered. The potential factors affecting derailment are screened according to field investigations of a train derailment case at the through route of a turnout. A detailed wagon-turnout interaction model considering the non-uniform cross-sections of turnout rails and the interaction between adjacent wagons is developed and validated. Through numerical simulation, the dynamic performance of an empty wagon passing the through route of turnout at a low speed is studied. When the wagon passes the turnout under the continuous lateral force condition, the wheels climb onto the rail head at the switch area in the facing direction, while the derailment occurs at the frog area in the trailing direction. Moreover, the possibility of derailment of the empty wagon increases with increasing coupler force and wheel-rail friction coefficient, and with decreasing speed. To improve the safety of empty wagons in the turnout area, rail lubrication should be implemented to reduce the wheel-rail friction coefficient, and large braking forces should be avoided. Furthermore, the wheel surface condition after re-profiling requires continuous attention. [ABSTRACT FROM AUTHOR]

A cab-based track monitoring system has been developed which makes use of the existing on-board GSM-R cab radio present in the majority of trains operating in the UK. With the addition of a low-cost sensor, type, location and severity of the track defects are reported using the system. The system improves safety and network performance by efficiently directing maintenance crews to the location of defects, minimising time spent on maintenance and inspection. Initially, vehicle dynamic simulation was used to test the feasibility of the system for defect monitoring and to develop compensation factors for vehicle type and operating speed. Novel on-board signal processing techniques are also presented through comparison of vibration response from sites with known defects and outputs from Network Rail's (NR) New Measurement Train (NMT). Good agreement was reported for track faults in relation to vertical and lateral alignment and dip faults. Statistically, good agreement has been demonstrated, suggesting that the data acquired could be used to provide an indication of track quality thereby improving network performance, reducing rough ride and leading to improved passenger comfort. Improvements in the measured and statistical correlation are anticipated through the use, of multi-train / multi-journey and machine learning methods. [ABSTRACT FROM AUTHOR]

Due to super elevation and centrifugal force, close attention is needed to lateral stability of cargo when the train negotiates curves. To guarantee the security of cargo on wagons, proper blocking, bracing and lashing are essential. In this study, we implement a cargo–wagon–rail coupling model that adopts diagonal lashing to restrain cargo movement. A preliminary dynamic simulation analysis demonstrates that the selected cargo tilts when the wagon negotiates curves. The quasi-static analysis reveals the cargo force condition and the key role of lashing stiffness. Coupling models are endowed with various lashing stiffness values. The curving performance of each model is evaluated considering different running conditions. The results indicate that increasing lashing stiffness reduces lateral cargo vibration and increases lashing tension force until the stable state. The cargo movement in this study is proved to have no significant effect on the wheel–rail interaction. Based on simulation results, this paper determines the diagonal lashing. It is demonstrated that the use of dynamic simulation to calculate the diagonal lashing force will improve cargo stability and avoid unnecessary expenditure on load restraint assemblies. Finally, it is proved that the promotion of pre-tension force is not necessary for diagonal lashings. [ABSTRACT FROM AUTHOR]

Ride comfort indices are used to evaluate the vibration of rail vehicles and to measure the discomfort of passengers. Among the various ride comfort indices, the Sperling index is widely used in China and other countries. However, there are several different methods for determining the Sperling index from dynamic simulations and performance measurements of rail vehicles, and the results obtained by different algorithms are inconsistent. It is therefore difficult to make an accurate evaluation with the different calculation results. In this paper, a comparison is made between algorithms based on time domain and frequency domain analysis and using the second and third powers of the acceleration. The different algorithms are then summarised into a unified equation, and the consistency of the results is analysed by this equation. It is found that only the r.m.s-based algorithm in the time or frequency domain is stable when analysis is carried out over different sample times. The time-frequency consistency of the r.m.s-based algorithms is verified by Parseval's theorem and using calculation results from time domain simulations. [ABSTRACT FROM AUTHOR]

This paper introduces a new type of suspended monorail developed in China with the advantages of both German and Japanese monorails. The FE (finite element) model of the bridge is built in Ansys and coupled with the multibody dynamic model of the vehicle in the UM (Universal Machine). software. FIALA formula is used to construct the tire model. Then, the vehicle-bridge coupling system of the new type suspended monorail is set up and simulated with Park method. The result of the modal analysis and vehicle-bridge coupling simulation draw the same conclusion that the span of the stiffeners could result in the resonance of the vehicle system, which is due to the coupling of the frequencies of the natural modes of the car body and bogie with that for vehicle passing through stiffeners. Through the multibody dynamic simulation of the vehicle-bridge coupling system, the modes of the bridge at the frequencies of 5–10, 15–25 and 30–40 Hz are easily excited when the vehicle passes through the bridge. The three constraint modes and free modes of the bridge are similar in these frequency ranges. [ABSTRACT FROM AUTHOR]

A wheel flat is a common fault in railway vehicles that may develop after incorrect brake application, or localised wheel-rail adhesion reduction. Operators detect wheel flats using wayside systems that are not capable of delivering real-time alarms. A wheel flat defect was modelled and introduced to a railway wagon multibody dynamic simulation to study the vehicle dynamic behaviour triggered by such wheel tread defect. Bogie-based and car body-based wheel flat detection was evaluated to determine eventual hardware robustness and signal processing requirements for on-board wheel flat detection devices. Various vehicle operating conditionds and wheel flat defects were simulated to analyse the wheel flat impact propagation throughout the railway vehicle bodies. Wheel defect detectability was assessed using detectability indicators (DIs) based on envelope power spectrum analysis, crest factor and RMS. It was found that bogie and car body-based wheel flat detectability is highly dependent on the track characteristics. The wheel flat signature was reduced in the wheelset-bogie and bogie-car body interfaces, indicating that advanced signal processing techniques are required for bogie-based and car body-based wheel flat detection systems. The DIs showed clear differences between healthy and faulty wheelset and bogie frame acceleration signals, which is promising for eventual on-board wheel flat detection systems. [ABSTRACT FROM AUTHOR]

The number of operating high-speed trains in China is around 2800 today and 179,200 wheels are under maintenance in one reprofiling period. To help researchers to understand the evolution of the wheel profile and improve the reprofiling strategy of the wheels, this study predicts the development of wheel profiles on a high-speed train as function of mileage and compare simulated worn wheel profiles with measured ones. The methodology includes transient multi-body dynamic simulation, wheel–rail contact calculation and wear calculation with Archard's model. Calibrated by analysing measurements of worn S1002CN profiles and performing parameters sensitivity study in the wear model, the model is then used to predict the development of a recently designed wheel profile, called S1002CN-RF. The simulation results for S1002CN and S1002CN-RF show that the predicted wheel profiles coincide with the measured ones. Wear prediction of another high-speed wheel profile (LMA) validates that the vehicle performance with respect to wear could be further improved compared to using S1002CN or S1002CN-RF. Finally, the influence of track alignment and operating speed is investigated. The wear increases with the speed increasing up to 300 km/h, but stays almost constant with a further speed increase from 300 to 400 km/h. [ABSTRACT FROM AUTHOR]

Modelling and simulation of wheel profile evolution is a time-consuming process in which the variables that affect simulation cases are usually selected and tuned through an iterative process, in order to find the right setup for a specific case. In a previous work, a fast and reliable methodology for wear prediction was developed, systematic and applicable in general terms for any arbitrary network, vehicle fleet or operating conditions. Here variables that influence the running behaviour of the vehicle along a track were classified into two groups (deterministic or statistical), according to the kind of method to be used to consider them in the wear calculation process. The deterministic method was already defined in [1], while this paper focuses on the definition of the statistical method. This methodology is illustrated through the study of track irregularities: first, their actual effect on wear is analysed and then, their representation as stochastic variables in the developed methodology is presented. The whole methodology is based on quasi-static simulations instead of dynamic simulations for calculating the wheel-rail contact parameters, so a special effort is made in ensuring that, when these parameters are defined by a statistical method, the methodology for wear estimation continues being valid. [ABSTRACT FROM AUTHOR]

The bogies of the Hitachi and Bombardier straddle-type monorail vehicles could not be in the radial state on the circular curve because of the constraints of their own structure or secondary suspension system. Therefore, a large load always existed on the guiding wheels, restricting the curve negotiation speed of the vehicle. Taking this as the starting point, this study aimed to propose a newly designed bogie, called the automatic radial coupled-bogie (ARC-bogie). The theoretical model of linear steady-state curve negotiation of the ARC-bogie was established to analyse the passive radial adjustment mechanism of the ARC-bogie, and the calculation method for the optimal coupled parameters required for achieving the radial state was proposed. To validate the theoretical model, the dynamic performance of the ARC-bogie and the influence of coupled parameters were analysed by dynamic simulation. The result showed that the coupled rotary stiffness could make the ARC-bogie achieve the radial state automatically on the circular curve under reasonable matching between the secondary suspension system and the coupling mechanism. Moreover, the maximum radial force of the guiding wheels decreased obviously, and the curve negotiation safety of the vehicle improved remarkably. Finally, a scheme for the coupling mechanism of ARC-bogie was proposed. [ABSTRACT FROM AUTHOR]

Repoint is an alternative concept for the design of track switches developed at Loughborough University. The concept, based around a stub switch, offers several improvements over current designs. Through a novel locking arrangement, it allows parallel, multi-channel actuation and passive locking functions, providing a high degree of fault tolerance. The aim of the work presented in this paper is to evaluate the dynamic interaction forces due to the passage of rolling stock over the switch and, particularly, the area of the stub rail ends, in comparison to a conventional switch. Specific behaviour and load transfer conditions from one rail to the other at the joint are analysed, as well as long-term wear conditions of the rails. These evaluations are undertaken by means of multi-body dynamic simulations, leading to design refinement of the stub rail ends and the identification of further research and development requirements in their design. [ABSTRACT FROM AUTHOR]

In multi-body dynamics, we model a non-conformal wheel/rail contact at one centre point since this contact is flat and Hertzian. However, the quasi-conformal contact requires more points since the contact is curved and non-Hertzian. The methodology in solving these points during dynamic simulations is the basis of this development. In this online effort, first, we present a general contact joint and the gutter search method of Pascal and Jourdan [The rigid-multi-Hertzian method as applied to conformal contacts. USA: ASME; 2007] in the context of a multi-body approach. Next, by adopting the non-iterative approach, a subset of these points with positive profile interpenetrations is selected to idealise one curved contact by a set of multi-Hertzian patches for which the Hertz normal contact solution is available. Finally, the feasibility of this multibody approach together with its implementation in two different codes is evaluated by simulating the motion of an isolated wheelset with realistic inertia. On tangent tracks, the wheelset with non-conformal pairing displays self-excited unstable oscillations while it displays a stable behaviour below a critical speed with conformal profiles. A further study reveals the net friction losses at multiple patches within the curved contact being the reason for the stable behavior. [ABSTRACT FROM AUTHOR]

This paper presents a review of various works that highlight the importance of introducing the variability of the road-track/vehicle system into dynamic simulations as soon as this latter is meant to be predictive. The first section of the paper presents the Uncertainty Quantification, Verification and Validation method (UQ-VV). This latter proposes tools to model uncertainties, to associate a confidence to the prediction of quantities of interest and to estimate the probability of occurrence of different scenarios. The method is illustrated by various examples mainly from the rail domain but also from the road sector. The second section summarises application examples of predictive modelling, robust optimisation and calibration. [ABSTRACT FROM AUTHOR]

The simulation of the pantograph-catenary dynamic interaction is at present mainly based on deterministic approaches. However, any errors made during the catenary stringing process are sources of variability that can affect the dynamic performance of the system. In this paper, we analyse the influence of dropper length, dropper spacing and support height errors on the current collection quality by applying a classic Monte Carlo method to obtain the probability density functions of several output quantities. The effects of installation errors are also studied for a range of train speeds. Finally, the pre-sag that, on average, produces the best behaviour of the system is identified, allowing for the uncertainty in the catenary installation. The results obtained show the convenience to consider variability in pantograph-catenary dynamic simulations. [ABSTRACT FROM AUTHOR]

This investigation demonstrates the wheel wear evolution and related vehicle dynamics of high-speed trains with an operating distance (OD) of around two million kilometres. A long-term experimental test lasting two years was conducted to record the wheel profiles and structural vibrations of various trainsets. The wheel wear, namely the profile shape, worn distribution and wheelset conicity, is investigated for several continuous reprofiling cycles. Typical results are illustrated for the stability analysis, and the ride quality is examined with increasing OD. In addition, the vibration transition characteristics between suspensions are investigated in both the time and frequency domains. The experiments show that the dominant wear concentrates on the nominal rolling radius, and the wear rate increases with OD because of the surface softening resulting from the loss of wheel material. The vibration of structural components is aggravated by the increase of the equivalent conicity of the wheelset, which rises approximately linearly with the wheel wear and OD. High-frequency vibrations arise in the bogie and car body related to the track arrangement and wheel out-of-roundness, causing the ride comfort to worsen significantly. Additionally, the system vibration characteristics are strongly dependent on the atmospheric temperature. Summaries and conclusions are obtained regarding the wheel wear and related vehicle dynamics of high-speed trains over long operating times and distances. [ABSTRACT FROM AUTHOR]

The finite element (FE) method is essential for simulating vehicle dynamics with fine details, especially for train crash simulations. However, factors such as the complexity of meshes and the distortion involved in a large deformation would undermine its calculation efficiency. An alternative method, the multi-body (MB) dynamics simulation provides satisfying time efficiency but limited accuracy when highly nonlinear dynamic process is involved. To maintain the advantages of both methods, this paper proposes a data-driven simulation framework for dynamics simulation of railway vehicles. This framework uses machine learning techniques to extract nonlinear features from training data generated by FE simulations so that specific mesh structures can be formulated by a surrogate element (or surrogate elements) to replace the original mechanical elements, and the dynamics simulation can be implemented by co-simulation with the surrogate element(s) embedded into a MB model. This framework consists of a series of techniques including data collection, feature extraction, training data sampling, surrogate element building, and model evaluation and selection. To verify the feasibility of this framework, we present two case studies, a vertical dynamics simulation and a longitudinal dynamics simulation, based on co-simulation with MATLAB/Simulink and Simpack, and a further comparison with a popular data-driven model (the Kriging model) is provided. The simulation result shows that using the legendre polynomial regression model in building surrogate elements can largely cut down the simulation time without sacrifice in accuracy. [ABSTRACT FROM AUTHOR]

Designs and analyses of seat-suspension systems are invariably performed considering effective vertical spring rate and damping properties, while neglecting important contributions due to kinematics of the widely used cross-linkage mechanism. In this study, a kineto-dynamic model of a seat-suspension is formulated to obtain relations for effective vertical suspension stiffness and damping characteristics as functions of those of the air spring and the hydraulic damper, respectively. The proposed relations are verified through simulations of the multi-body dynamic model of the cross-linkage seat-suspension in the ADAMS platform. The validity of the kineto-dynamic model is also demonstrated through comparisons of its vibration transmission response with the experimental data. The model is used to identify optimal air spring coordinates to attain nearly constant natural frequency of the suspension, irrespective of the seated body mass and seated height. A methodology is further proposed to identify optimal damping requirements for vehicle-specific suspension designs to achieve minimal seat effective amplitude transmissibility (SEAT) and vibration dose value (VDV) considering vibration spectra of different classes of earthmoving vehicles. The shock and vibration isolation performance potentials of the optimal designs are evaluated under selected vehicle vibration superimposed with shock motions. Results show that the vehicle-specific optimal designs could provide substantial reductions in the SEAT and VDV values for the vehicle classes considered. [ABSTRACT FROM PUBLISHER]

A precise estimation of vehicle velocities can be valuable for improving the performance of the vehicle dynamics control (VDC) system and this estimation relies heavily upon the accuracy of longitudinal and lateral tyre force calculation governed by the prediction of normal tyre forces. This paper presents a computational method based on the unscented Kalman filter (UKF) method to estimate both longitudinal and lateral velocities and develops a novel quasi-stationary method to predict normal tyre forces of heavy trucks on a sloping road. The vehicle dynamic model is constructed with a planar dynamic model combined with the Pacejka tyre model. The novel quasi-stationary method for predicting normal tyre forces is able to characterise the typical chassis configuration of the heavy trucks. The validation is conducted through comparing the predicted results with those simulated by the TruckSim and it has a good agreement between these results without compromising the convergence speed and stability. [ABSTRACT FROM PUBLISHER]

Real road vehicle tests are time consuming, laborious, and costly, and involve several safety concerns. Road vehicle motion simulators (RVMS) could assist with vehicle testing, and eliminate or reduce the difficulties traditionally associated with conducting vehicle tests. However, such simulators must exhibit a high level of fidelity and accuracy in order to provide realistic and reliable outcomes. In this paper, we review existing RVMS and discuss each of the major RVMS subsystems related to the research and development of vehicle dynamics. The possibility of utilising motion simulators to conduct ride and handling test scenarios is also investigated. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of four models of rolling contact used for online contact force evaluation in rail vehicle dynamics. Until now only a few wheel–rail contact models have been used for online simulation in multibody software (MBS). Many more models exist and their behaviour has been studied offline, but a comparative study of the mutual influence between the calculation of the creep forces and the simulated vehicle dynamics seems to be missing. Such a comparison would help researchers with the assessment of accuracy and calculation time. The contact methods investigated in this paper are FASTSIM, Linder, Kik–Piotrowski and Stripes. They are compared through a coupling between an MBS for the vehicle simulation and Matlab for the contact models. This way the influence of the creep force calculation on the vehicle simulation is investigated. More specifically this study focuses on the influence of the contact model on the simulation of the hunting motion and on the curving behaviour. [ABSTRACT FROM AUTHOR]

Significant advances made on the rolling stock have considerably increased the possibility of higher speeds in existing railways. Thus, it is important to explore higher speeds and potential limiting factors of existing soft catenary systems. The present paper investigates procedures to assess the dynamic behaviour of these systems using response sampling and modal analysis. The assessment evaluates and quantifies dynamic response along the section. To verify the approach, a case study is conducted and the following assessment methods are used: lengthwise track correlation estimating dynamic predictability, power spectral density estimations before and after passage and short-time Fourier transforms and spectrograms. The combination provides detailed information on the dynamic behaviour. The first part introduces necessary considerations for suggested modal analysis. The second part describes an existing Norwegian section. The case study is conducted using a finite element model including a straight and a given section between Oslo-Trondheim, providing detailed evaluations and system limitation detections. [ABSTRACT FROM AUTHOR]

A model for simulation of dynamic interaction between a railway vehicle and a turnout (switch and crossing, S&C) is validated versus field measurements. In particular, the implementation and accuracy of viscously damped track models with different complexities are assessed. The validation data come from full-scale field measurements of dynamic track stiffness and wheel–rail contact forces in a demonstrator turnout that was installed as part of the INNOTRACK project with funding from the European Union Sixth Framework Programme. Vertical track stiffness at nominal wheel loads, in the frequency range up to 20 Hz, was measured using a rolling stiffness measurement vehicle (RSMV). Vertical and lateral wheel–rail contact forces were measured by an instrumented wheel set mounted in a freight car featuring Y25 bogies. The measurements were performed for traffic in both the through and diverging routes, and in the facing and trailing moves. The full set of test runs was repeated with different types of rail pad to investigate the influence of rail pad stiffness on track stiffness and contact forces. It is concluded that impact loads on the crossing can be reduced by using more resilient rail pads. To allow for vehicle dynamics simulations at low computational cost, the track models are discretised space-variant mass–spring–damper models that are moving with each wheel set of the vehicle model. Acceptable agreement between simulated and measured vertical contact forces at the crossing can be obtained when the standard GENSYS track model is extended with one ballast/subgrade mass under each rail. This model can be tuned to capture the large phase delay in dynamic track stiffness at low frequencies, as measured by the RSMV, while remaining sufficiently resilient at higher frequencies. [ABSTRACT FROM AUTHOR]

Currently, pantograph–catenary dynamic simulations are mainly based on deterministic approaches. However, the contact force between catenary and pantograph depends on many key parameters that are not always quantified precisely and can vary in time and space. To get a better chance of addressing extreme or combined critical conditions, methodologies to consider variability are thus necessary. Aerodynamic forces and geometrical irregularities of catenaries are thought to be significant sources of variability in measurement and this paper proposes methods to take them into account. Results are compared with measurements to correlate the effect of the considered parameters with experimentally observed variability. Finally, a virtual certification example is shown, with a study of the influence of speed on the impact of variability. [ABSTRACT FROM PUBLISHER]

To study the dynamic response of a railway vehicle occupant during collision, a multi-car coupling collision model was set-up to obtain velocity and acceleration data for every car, and occupant secondary impact velocity (SIV) plots, which were applied to the car body – passenger compartment – dummy coupling model. Then the performance index results for the dummy, its governing movement laws, head acceleration response, and the relationship between performance index and SIV were obtained for each car by analysis under different conditions. The results indicated that both the head injury and thoracic cumulative 3 ms injury criteria increased with increasing SIV. The velocity of the dummy in Car 3 (moving) and Car 7 (static before impact) was greatest when the occupant faced a table: the corresponding head injury ratings were 669.9 and 606.0, respectively, and the thoracic ratings were 656.2 and 641.4 m/s2. [ABSTRACT FROM AUTHOR]

A key factor to understand the vehicle dynamic behaviour is to know as accurately as possible the interaction that occurs between the tyre and the road, since it depends on many factors that influence the dynamic response of the vehicle. This paper aims to develop a methodology in order to characterise the tyre–road behaviour, applying it to obtain the tyre–road grip coefficient. This methodology is based on the use of dynamic simulation of a virtual model, integrated into a genetic algorithm that identifies the tyre–road friction coefficient in order to adjust the response obtained by simulation to real data. The numerical model was developed in collaboration with SEAT Technical Centre and it was implemented in multibody dynamic simulation software Adams®, from MSC®. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a three-dimensional multibody system (MBS) for the dynamic simulation of rope-propelled automated people movers (RAPM). These public transport systems include guided vehicles which operate in a fully automated mode on a separate guideway. In design stage of an RAPM the optimisation of ride comfort and durability is aspired. Therefore, an elastic rope model has been implemented in a state-of-the-art MBS software. The coupling of the rope model with standard MBS elements allows for the integrated simulation of these transport systems which will enhance the prediction quality of the overall system dynamics. [ABSTRACT FROM AUTHOR]

Testing of the running characteristics of railway vehicles requires well-defined boundary conditions like track geometry quality. Test sections with the same track geometry quality must lead to the same dynamic vehicle response (VR) forces. The state-of-the-art methods do not fulfil this important requirement for a track quality definition. Our proposed method for track geometry assessment considers the vehicle/track interaction. 'Representative' transfer functions are used for the prediction of the vehicle reaction. Therefore, the results show a significant enhancement of the correlation between the track assessment quantities and the VR forces. [ABSTRACT FROM AUTHOR]

A loaded freight vehicle with two three-piece bogies is modelled using the accessible mathematical software MATLAB. The results are compared with its corresponding ADAMS/Rail dynamic multibody simulation model, where similar derailment factors are encountered for the freight vehicle. Both models reveal that the possibility of derailment increases immediately after entering and at the end of the curve - signifying the beginning and the end of the curve as two major points for derailment. Although a three-piece bogie construction is rather simple, its mathematical model proves to be very complex and is nonlinear due to the reported frictional contact at the rail/wheel interface as well as the friction wedges. This research is stimulated by bogie derailments that have occurred in the Iranian railways as well as those in the rest of the world. [ABSTRACT FROM AUTHOR]

To investigate the lateral vibration mechanism of middle cars of Shinkansen train in tunnel section, field tests and numerical simulations are performed. From the analysis of car body vibration and air pressure around the carbody, the following results are obtained. (1)The pressure fluctuation on the wall side of the carbody is correlated with the lateral vibration in tunnel section. (2)The yawing vibration mode tends to become dominant. (3)The dominant frequency increases and the negative damping is added to the original carbody dynamic system as the running speed increases. From these results, it is suggested that the lateral vibration is related to the interaction of the carbody vibration and the gap flow fluctuation between the carbody and the tunnel wall. From a numerical vehicle dynamic simulation including flow fields with moving boundaries, the following results are obtained. (1) The energy from fluid may continues carbody vibration in yawing motion which are observed largely in the field test data. (2) The damping of carbody vibration decreases with the flow field. [ABSTRACT FROM AUTHOR]

Modelling and simulation of the dynamic behaviour of catenary-pantograph interaction is an important part when assessing the capability of a current collection system for railway traffic. The large variation in infrastructure characteristics in different countries and railway companies, different types of traffic, designs of pantographs etc. makes it almost impossible to develop a final simulation model of such a system. Instead, it would be favourable to have a tool that has the ability to set up models of such systems, choose relevant detail of the models, run simulations and finally visualise the results. To make the tool useful for engineers, design experts as well as simulation experts, the functionality of the tool must be worked out. Aspects on computer simulation such as developed models, simulation methods and computer tools are presented. The aim is to develop a scenario that considers different designs, models, solution methods and user levels. The scenario focuses on how to structure the use of simulation of dynamics in catenary-pantograph development. A scenario is sketched built on different user levels, a modular structure and a structure for information management. [ABSTRACT FROM AUTHOR]

New pantograph concepts require an integrated development environment for it's design process. The set up of dynamic models and the simulation of the interaction between pantographs and catenaries are essential to evaluate enhanced mechatronic design concepts. The introduced simulation environment enables investigations on new approaches for the complete system as well as for single components. For verification tasks, a detailed simulation model of the pantograph was set up directly according it's design data. Different control concepts were adjusted using a specialized analysis program for control units. In particular, the co-simulation between a standard MBS1 and a specific catenary simulation program made a more precise prediction of the dynamic behaviour possible. First proposals of mechatronic concepts for certain components of a present high performance pantograph demonstrated the efficiency of the realized CAE2-concept. [ABSTRACT FROM AUTHOR]