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High-precision tracking control is very important in high-speed train (HST) operation. This study proposes an adaptive global terminal sliding mode control scheme based on limited error (AEG-SMC) for trajectory tracking of HST. AEG-SMC is firstly proposed for the nonlinear dynamic system to improve the accuracy of tracking error and solve the problem of parameter uncertainty in the model. Then, AEG-SMC uses an adaptive method to approximate the uncertain parameters in the model to obtain real-time parameter estimation, and an error index function is given to realise fast and high-precision tracking of the system by global terminal sliding mode control (GSMC). AEG-SMC is able to design the required error indicators before conducting control, thereby ensuring the high-quality response and stability of the system. Finally, the simulation results show that the speed tracking error and control input of HST with AEG-SMC are also the smallest among the mentioned methods. [ABSTRACT FROM AUTHOR]

The rubber joints mounted on swing arms provide the main part of the yaw stiffness for wheelsets and thus have a significant influence on the dynamic behaviour of railway vehicles. However, their nonlinear dynamic properties concerning the frequency, amplitude, and temperature were not fully considered in previous studies, most of which adopt simple models such as the Kelvin–Voigt model to represent rubber components. This study aims to investigate the radial nonlinear properties of swing arm rubber joints under various conditions and assess their effects on the dynamic performance of high-speed trains. A nonlinear rubber spring model which combines the fractional derivative Zener model with Berg's friction model is established. To achieve a better fit to the measurements of a swing arm rubber joint, an optimisation-based method is employed to identify the model parameters. The viscous and frictional effects of the rubber joint are compared at different frequencies, amplitudes, and temperatures, by determining the predominant element of the nonlinear model. Additionally, the nonlinear rubber spring model is integrated into a high-speed vehicle dynamic model to investigate the effects of the nonlinear properties of swing arm rubber joints on the vehicle dynamic behaviour through the MATLAB/SIMPACK co-simulation method. [ABSTRACT FROM AUTHOR]

When a high-speed train is parallel with a pipeline, its power supply system provokes alternating current (AC) interference that results in the corrosion of the pipeline and a risk of electric shock to pipeline workers. Because trains are continuously moving, the AC interference on the pipeline changes, making mitigation design difficult. In this study, we used numerical simulation to study how the location of a high-speed train influences a pipeline. The results revealed the following: (1) AC interference on a pipeline mainly depends on the current in the rail, because a large amount of current leaks from the rail to the earth, generating a current imbalance. (2) While a train is running from TPSS to AT2, AC voltage peaks appear at the beginning, the ending of the parallel segment, and the middle of each AT section; therefore, the mitigating measurement, if needed, should be the priority at these positions. (3) Compared to the interference caused by a single train, the interference on pipeline is not doubled, but only increases slightly. Moreover, interference reaches its maximum not when two trains are at 5 and 15 km, but when they are at AT1 and 15 km. (4) Field testing was conducted on an actual gas pipeline in the Beijing area. The results showed that the field-tested AC voltage of the pipeline was generally consistent with the calculations. [ABSTRACT FROM AUTHOR]

Studies on wheel flatness and polygonal wear have demonstrated that wheel defects cause severe impact forces at the wheel–rail interfaces. This study investigated the dynamic contact mechanical behaviour of high–speed train transmission gears when subjected to wheel defects. First, a train-track coupling dynamics model was established, considering the localized contact characteristics of transmission gears. This model was developed using the slice method and the Hertz contact model, exploring the spatial coupling effects between the gear contact interface and the train–track interface. Subsequently, the dynamic model was employed to extract essential contact mechanical parameters of the transmission gear under the influence of wheel defects, including gear meshing load, gear contact stress, and sliding velocity. Furthermore, an analysis was conducted to uncover and elucidate the mechanism by which wheel flatness and polygonal wear impact the dynamic contact behaviour of the transmission gear. This study underscores the importance of considering wheel defects when assessing the contact fatigue and wear performance of high-speed train transmission gears. [ABSTRACT FROM AUTHOR]

The continuous increase in the operating speed of rail vehicles demands higher requirements for passive safety protection and lightweight design. This paper focuses on an energy-absorbing component (circular tubes) at the end of a train. Thin-walled carbon fiber-reinforced polymer (CFRP) tubes were prepared using the filament winding process. Through a combination of sled impact tests and finite element simulations, the effects of a chamfered trigger (Tube I) and embedded trigger (Tube II) on the impact response and crashworthiness of the structure were investigated. The results showed that both triggering methods led to the progressive end failure of the tubes. Tube I exhibited a mean crush force (MCF) of 891.89 kN and specific energy absorption (SEA) of 38.69 kJ/kg. In comparison, the MCF and SEA of Tube II decreased by 21.2% and 21.9%, respectively. The reason for this reduction is that the presence of the embedded trigger in Tube II restricts the expansion of the inner plies (plies 4 to 6), thereby affecting the overall energy absorption mechanism. Based on the validated finite element model, a modeling strategy study was conducted, including the failure parameters (DFAILT/DFAILC), the friction coefficient, and the interfacial strength. It was found that the prediction results are significantly influenced by modeling methods. Specifically, as the interfacial strength decreases, the tube wall is more prone to circumferential cracking or overall buckling under axial impact. [ABSTRACT FROM AUTHOR]

This paper focuses on the event-triggered consensus tracking of high-speed trains under denial-of-service (DoS) attacks. A novel anti-disturbance control strategy is proposed, based on an adaptive memory state observer and a disturbance observer. A memory is introduced to buffer system output information which enhancing the precision of the state observer, and the gust disturbance during the high-speed train operation is estimated by the disturbance observer. The Linear Matrix inequality technique is used to obtain the observer feedback coefficient and the controller gain, and the Lyapunov theory is employed to demonstrate the controller's consistency tracking performance. Applying the memory to the event-triggered mechanism, a new adaptive memory event-triggered scheme is designed to better ensure system performance and effectively prevent the occurrence of Zeno behavior. To achieve precise identification of DoS attacks in the event-triggered environment, a new detection algorithm is proposed. Finally, simulation examples are used to validate the effectiveness and practicality of the proposed scheme. [ABSTRACT FROM AUTHOR]

This study presents the validation of a dynamic test system to simulate a high‐speed train passing bridges under seismic excitation. The system comprises scaled models of a CRH380A high‐speed train and an 11‐span simply supported bridge on a shake table array. This innovative apparatus combines seismic loading with the moving train load to replicate train‐track‐bridge interaction (TTBI) during earthquakes. It allows investigation of various train speeds and seismic excitations, providing invaluable insights into TTBI. First, the detailed similarity design principle based on the equations of motion was discussed, and its applicability to the wheel‐rail contact relationship was verified. Then, the dynamic characteristics of the scaled model were identified, and the impact of the error between the scaled model and the theoretical model on the TTBI response was assessed. Furthermore, the comparison of the dynamic test model and the numerical simulation in acceleration responses validated the accuracy of the rigid‐flexible coupling model method for the actual TTBI system. Test cases without external excitation, with simple harmonic excitation and with seismic excitation were conducted on the dynamic test system. Results showed that the influence of track irregularity and running speed on train response aligns with the classical train‐bridge interaction theory. The successful implementation of this test system marks a significant advance in understanding TTBI mechanics and has significant implications for seismic safety enhancement of railway infrastructure. [ABSTRACT FROM AUTHOR]

There are excessive inter-car lateral vibrations of the current Chinese CRH1 high-speed train, so it is meaningful to improve the high-speed train dynamics by optimising its inter-vehicle suspension. Multi-body system (MBS) dynamics modelling of CRH1 high-speed train with inter-vehicle suspension was first performed in this study, then the MBS model was used to analyse the influential mechanism and the quantitative effects of inter-vehicle damper parameters on vehicle system dynamics, the design of experiment (DOE) approach was finally applied to optimise the inter-vehicle damper parameters. Simulation results showed that after the optimisation, there was a significant reduction in the inter-car lateral accelerations of CRH1 with a maximum rate of 20.1%, in addition, the severe lateral shock and oscillation, especially car roll acceleration, that are induced by aerodynamics when two high-speed trains pass each other were significantly suppressed with a maximum rate of 25%. Thus, the developed MBS model and the obtained optimisation result provide the basis for an engineering solution of the problem of excessive inter-car lateral vibrations of CRH1, the obtained knowledge of inter-vehicle damper parameter effects on high-speed train dynamics are valuable in the context of development of inter-vehicle suspensions for high-speed trains. [ABSTRACT FROM AUTHOR]

Early fault diagnosis of suspension systems is essential for the safe operation of high-speed trains. However, neural network-based fault diagnosis methods have two remaining issues: the fault samples are difficult to obtain in practice and the early fault features are too weak to be extracted directly from the raw vibration signals using neural networks. A novel strategy is proposed for early faults diagnosis in suspension systems (i.e. component performance degradation within 20%) by integrating a new sample reconstruction method, a new grouping normalisation method, and model-agnostic meta-learning (MAML) algorithm. First, the 1D raw vibration signals are converted to 2D feature matrices consisting of artificial features using the sample reconstruction method; meanwhile, the grouping normalisation method is used to enhance the early weak fault features in the feature matrices. Second, MAML specialises in few-shot model training for early fault diagnosis, with the feature matrices as the training samples. Finally, the results are compared with those obtained using other current methods. The numerical results show that the proposed strategy yielded excellent performance in the few-shot early faults diagnosis of suspension systems, achieving a maximum accuracy of 94.75%. [ABSTRACT FROM AUTHOR]

This study investigates the aerodynamic performance of various trains with different nose shapes, using as the design variables two angles α , β for the head shape and the bluntness angle γ , without crosswind. The effects on aerodynamic performance, such as the train drag coefficient, pressure distribution along the train surface, flow structures around the train and the wake, and head pressure pulse, are analyzed. The results indicate that the increase in the train nose length for flat shapes decreases the C D values by 21.47 % and 19.11 % , decreasing the high-pressure region in the leading head. The duck nose configuration emerges as a compromise between drag reduction and nose length. Increasing the angle γ , a further drag reduction of 8.5 % is featured. Drag formation along the train is also analyzed. The steeper the variation in the geometry, the higher the peak intensity and the slope of the curve. Regarding the flow features around the train, two main counter-rotating vortices are captured in the wake. Moreover, the higher the nose length and the higher the bluntness angle γ , the weaker and narrower the wake. Again, a longer nose shape yields a softer jump in terms of pressure difference, crucial for train homologation and safety. [ABSTRACT FROM AUTHOR]

Copyright of Urban Mass Transit is the property of Urban Mass Transit Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the problem of speed cruise control in high-speed trains, which are modeled as large-scale systems with each car considered as an independent subsystem. Decoupled H ∞ controllers are employed for each car. To address parameter uncertainties and time-varying delays, a comprehensive analysis of the robustness and time-delay stability of the large-scale system was conducted, which led to the design of decoupled controllers. Simulations and comparative analyses were conducted to validate the correctness of the control algorithm and demonstrate the feasibility of controlling high-speed trains as large-scale time-delay systems. This study has yielded theoretical results in large-scale system control, successfully applying results to high-speed train control. The idea and method offer new perspectives and lay the foundation for addressing more complex issues in high-speed trains. [ABSTRACT FROM AUTHOR]

To investigate the influence of snow particle rotational motion on the accumulation of snow in the bogie region of high-speed trains, an Euler‒Lagrange numerical approach is adopted. The study examines the effects of snow particle diameter and train speed on the ensuing dynamics. It is shown that considering snow particle rotational motion causes significant deviation in the particle trajectories with respect to non-rotating particles. Such a deviation increases with larger snow particle diameters and higher train speeds. The snow accumulation on the overall surface of the bogie increases, and the amount of snow on the vibration reduction device varies greatly. In certain conditions, the amount of accumulated snow can increase by several orders of magnitudes. [ABSTRACT FROM AUTHOR]

Three triangular friction block configurations are commonly employed in high-speed train brake systems, namely, unperforated, perforated configuration with one circular hole, and perforated with three circular holes. In this study, we adopted these friction block types to investigate the effect of perforated friction block configurations on the brake performance of high-speed trains based on a self-developed brake test rig. The results indicate the significant impact of the number of the holes on the wear behavior, temperature distribution, and vibration characteristics of the brake interface. The friction surface of the unperforated block is covered by wear debris, while the perforated blocks produce less wear debris. Furthermore, the one-hole block exhibits a more uniform temperature distribution and better vibration behavior than that with three holes. The friction brake is a dynamic process, during which separation and attachment between the pad and disc alternatively occur, and the perforated structure on the friction block can both trap and expel the wear debris. [ABSTRACT FROM AUTHOR]

The brake system is a key component of a high-speed train, which suffers intense wheel-rail interactions caused by wheel polygonal wear (WPW) in realistic working conditions. To explore the dynamic characteristics of the disc brake systems with WPW, a rigid-flexible coupled vehicle dynamics model is proposed. The developed model systematically takes into account the flexible deformation of brake components and wheelsets, measured WPW and non-linear factors such as wheel-rail interaction, disc-pad friction and non-linear damping characteristics. It allows the dynamic behaviors of the vehicle brake system in service to be accurately and effectively revealed. The model is verified using line test data, and then the dynamic characteristics of disc brake systems with WPW are investigated in details. The results show that for vehicle speed below 80 km/h and depths of WPW below 0.04 mm, the effect of WPW on the vibration of the caliper is slight. However, as vehicle speed and wear depth continue to rise, the vibration of the caliper increases noticeably. Furthermore, the effects of vehicle speed and wear depth on brake disc vibration are more obvious, and increasing vehicle speed and wear depth will steadily deteriorate the vibration of the disc. Besides, the effect of WPW is particularly pronounced on the dynamic behavior of the brake units closer to the wheels. Overall, the influence of wheel polygon cannot be neglected in the study of dynamic characteristics of brake system. At the same time, the proposed model can also be applied in the strength evaluation of brake components and the study of the tribological behaviors within the brake interface. [ABSTRACT FROM AUTHOR]

The increasing number of train–moose collision accidents threatens train running safety. This study investigated the bullet train–moose collision process and explored the effect of parameters on the dynamic responses. The multibody (MB) model was developed and validated against real–world collisions and the validated finite element model. A parametric study including the moose size, train speed, moose velocity, moose offset, and impact angle was conducted using MADYMO software. The lateral and longitudinal displacements of the moose's center of gravity (CG) were used to evaluate the crash safety. The results showed that the moose size significantly affects moose impact dynamics and kinematics. The velocity and the offset of the moose were positively correlated with the lateral displacement. However, there was an obvious nonlinear relationship between the train speed and the lateral displacement. With the increase in the collision speed, the front–end deformation weakens the obstacle removal effect of the front hatch. The landing spots of the small–sized moose were the most concentrated, which means greater risk of secondary collisions. This study provides practical help for improving the running safety of high–speed trains and protecting wild animals along railways. [ABSTRACT FROM AUTHOR]

The aerodynamic drag of high-speed trains has a negative effect on their running stability and energy efficiency. Since the shape of the high-speed train head closely influences its surrounding airflow, optimizing the head shape is the primary way to reduce the aerodynamic drag. However, existing optimization methods have limitations in parametrically describing the train head with enough details and fewer parameters. In this paper, we propose a novel parametric modeling method based on the approximate analytical partial differential equation (PDE) for the aerodynamic shape optimization of high-speed train heads. With this method, the detailed shape of the train head is controlled by four design parameters. To enhance the optimization efficiency, a two-stage multilayer perceptron (MLP) surrogate model is proposed to predict the aerodynamic drag coefficients of the high-speed train, and a classic genetic algorithm (GA) is adopted to optimize the total drag coefficient and generate the train head shape with good aerodynamic performance. The effectiveness of the proposed method is demonstrated through several comparison experiments. [ABSTRACT FROM AUTHOR]

In recent decades, the number of high-speed railways (HSRs) has increased due to the advancement of urbanization and modernization, the vibration caused by high-speed train (HST) has become an increasingly prominent problem. The vibration can result in irritability to inhabitants, settlement of foundation, and other damages. Therefore, it is vital to assess the vibration level and influences of the engineering geological conditions on vibration propagation. To this end, field investigation was performed on the special loess slope near embankment of Baoji–Lanzhou HSR in typical loess regions. And then the homogeneous (HOM) model and heterogeneous (HEM) model were constructed based on the geological data of this area. The acceleration responses of the special loess slope were comprehensively analyzed in time-history and frequential contents. The two-dimensional finite element method coupling with infinite element boundary was adopted to analyze the influences of engineering geological conditions on acceleration responses induced by HSTs. The results show that the peak acceleration and virtual value of acceleration do not monotonically decrease along the special loess slope, and their values are amplified at 35.3 from the track. The vibration energy is primarily concentrated in 25–75Hz, and the characteristic of each frequency band is affected not only by HST speed but also topography. Besides, the vibration intensity and duration of the special loess slope are larger than those of the flat site in the HOM and HEM models, and the vibration intensity of HEM model is obviously larger than that of HOM model. [ABSTRACT FROM AUTHOR]

In this paper, the unsteady aerodynamic characteristics of a three-car grouped high-speed train (HST) with different bogie fairing configurations under the crosswind are studied using improved delayed detached eddy simulation (IDDES) at Re = 1.85 × 106. The numerical method results are validated against the previous wind tunnel experiments. There are three cases with original half-fairing configuration (HFC), non-fairing configuration (NFC) and full-fairing configuration (FFC), respectively. The numerical results show that the bogie fairing configuration has significant effects. Compared to the HFC case, the drag force coefficients of the head, middle and tail cars with NFC increase by 53.13%, 14.87% and 27.04%, and corresponding parts of the FFC case decrease by 49.98%, 24.40% and 12.41%, respectively. The FFC case can also optimize the pressure distribution on the windward and leeward sides of the HST, and the flow structure and vertex distribution around the car body are also optimized. In addition, the increasing encirclement of the fairing configurations reduces the maximum lateral flow velocity inside the bogie cavities by 70% for HFC and 50% for FFC compared to the NFC. Overall, the FFC presents better aerodynamic performance than the NFC and HFC cases under crosswind, which is recommended for the design of the HST. [ABSTRACT FROM AUTHOR]

The temperature of axle box bearing is always one of the indicators used to monitor whether the high-speed train is running safely. In this paper, a thermal model of axle box bearing considering the change of bearing lubrication state and the operating condition of the high-speed train was established. Based on the analysis of the generation mechanism of frictional heat inside the bearing, the influence of proportion of grease involved in lubrication was introduced for the first time and a detailed temperature transfer system of the axle box system was established. At the same time, through the axle box bearing-vehicle system dynamics model, the vertical and lateral loads of the axle box bearing under different operating condition were obtained as input parameters of the axle box bearing thermal model, the temperature distribution curve of the bearing under different operating conditions was obtained. Finally, based on the long-term wireless transmission device system (WTDS) temperature monitoring data, the calculation results of the established model were verified. The verification results showed the reliability of the model established in this paper, and showed the necessity of considering the change of the internal lubrication state of the bearing when evaluating the axle box bearing temperature. [ABSTRACT FROM AUTHOR]

Axle-box bearings are directly affected by wheel–rail impacts as fixedly connected to wheelset. As an inevitable wheel-failure, wheel flat can cause severe wheel-rail impact, which may deteriorate the performance of axle-box bearings, even threatening train running safety. To investigate the dynamic response of axle-box bearings excited by wheel flat, two rigid-flexible coupled vehicle dynamics models of motor and trailer cars are developed. The axle-box bearing, flexible axle-box and wheelset are thoroughly established in trailer car model. The gear transmission system and flexible gearbox are further integrated into motor car model relative to trailer model. The accuracies of models are verified by the field-test results. The dynamic responses of axle-box bearings excited by wheel flat are analyzed. Results indicate that the vibration and dynamic forces acting on axle-box bearing augment with the increasing of flat length. The vibrations intensify gradually from wheelset, inner ring, and outer ring to axle-box, particularly increasing significantly with long flat lengths. Moreover, the dynamic forces within axle-box bearing first increase before decreasing with the growing operating speed. Being structurally difference, wheel flat exerts more significant effects on the axial and radial forces within the bearings of motor car than those of trailer car. [ABSTRACT FROM AUTHOR]

• The adaptive nonlinear damping is integrated into lateral suspension to improve hunting stability of high-speed train. • Three typical hunting bifurcations with different wheel/rail equivalent conicity functions are analyzed. • An adaptive constraint-following control method is employed to implement nonlinear damping via active suspension system. • The proposed method can significantly improve both carbody and bogie hunting stability. This study employs an active secondary suspension with adaptive nonlinear damping to enhance the hunting stability of high-speed trains. Adjusting passive suspension parameters to optimize ride comfort and hunting stability simultaneously in varied extreme operational conditions poses a significant challenge for high-speed trains. This research integrates high-order displacement-dependent nonlinear damping into the secondary lateral suspension, drawing on insights from field test data. We analyze three typical hunting motion bifurcations: carbody hunting and both subcritical and supercritical bifurcations of bogie hunting. Theoretical analysis demonstrates that (a) the adaptive nonlinear damping narrows the unstable speed range and reduces the amplitude of the limit cycle in carbody hunting, (b) while it does not increase the critical speed for supercritical bogie hunting bifurcation, it substantially reduces the amplitude of the limit cycle, and (c) it increases the nonlinear critical speed for subcritical bogie hunting bifurcation, with the potential to alter the bifurcation from subcritical to supercritical, which holds considerable practical significance. Implementing such nonlinear damping directly through passive structure is challenging. Therefore, in view of this underactuated control problem, the constraint-following control is applied in the active suspension system to inherit the benefits of adaptive nonlinear damping. The simulation results show that the proposed active suspension system can effectively suppress the abnormal vibration caused by hunting motions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hunting stability is an important performance criterion in railway vehicles. This study proposes an incorporation of a bio-inspired limb-like structure (LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains (HSTs). Initially, a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests. Subsequently, a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior. The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed. Then, the nonlinear damping of the bio-inspired LLS, which has a positive correlation with the relative displacement, can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system. Furthermore, a comprehensive numerical model of a high-speed train, considering all nonlinearities, is established to investigate the influence of different types of motor suspension. The simulation results are well consistent with the theoretical analysis. The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated. [ABSTRACT FROM AUTHOR]

The problem of ground dynamic response to a high-speed trainload has received much research attention in the literature, ranging from simplified analytical studies for elastic half-space to sophisticated numerical studies for layered or improved grounds. While most studies have focused on the dynamic response of a ground to a particular trainload, limited attention has been paid to comparing the dynamic response of a ground to different trainloads. In this study, we simulate the dynamic response of a layered ground to the passage of X2000 and Shinkansen trainloads. The obtained results are then compared to gain an understanding of how the ground responds to different trainloads. It is found that because the X2000 train and the Shinkansen train differ in carriage weights, carriage lengths, bogie distances and axle distances, they produce two trainloads whose magnitude and distribution of axle loads are different. As a consequence, they result in a difference in the surface deflection and displacement amplitudes. The difference in displacement amplitudes between the two train cases happens not only at the critical speed but also at all other considered train speeds (from 72 km/h to 360 km/h). On the other hand, although the X2000 train and Shinkansen train produce 2 trainloads that are different in magnitude and distribution of axle loads, they still result in the same critical speed of 252 km/h. This implies that the critical speed does not depend on the trainload type. Instead, it depends mainly on the specific wave propagation characteristics of the ground. [ABSTRACT FROM AUTHOR]

The effect of aerodynamic noise from high-speed trains on residents living near railway lines is a critical issue. The pantograph cavity is considered to be a major source of aerodynamic noise. To address this problem, this study proposes the application of jetting at the leading edge of the cavity, directly targeting noise reduction at its source. The large eddy simulation approach is used for flow calculations, and the Ffowcs Williams and Hawkings aeroacoustic analogy is adopted for far-field acoustic predictions. Orthogonal designs and the backpropagation algorithm optimized by the genetic algorithm (BP-GA) is used to explore the effects of jetting factors on noise and identify the optimal parameters. Orthogonal design analysis shows that the most influential among the factors is jet orifice diameter, followed by jet velocity and jet angle. The use of the BP-GA algorithm for optimization reveals that the optimal jet parameters are jet velocity of 118.28 m/s, jet angle of 3.17°, and jet orifice diameter of 76.74 mm. The algorithm predicts a minimum noise level of 91.04 dB, which is close to the simulated noise level of 90.74 dB. The jetting process achieves a maximum noise reduction of 4 dB. Results demonstrate that the proposed method for cavity leading edge jetting effectively reduces turbulent kinetic energy and horseshoe-shaped vortices in the cavity, leading to noise reduction. This method also minimizes the effects of aerodynamic noise on distant areas, such as waiting areas and residential buildings. This work provides a theoretical basis for increasing high-speed train speeds. [ABSTRACT FROM AUTHOR]

In the field of structural analysis dedicated to the study of vibrations of high-speed railway bridges, one reference load model is the well-known HSLM-A, which limits of validity are stated in Eurocode EN 1991-2, Annex E. In a recent paper published in the Journal of Rail and Rapid Transit, the authors investigated the degree of coverage provided by HSLM-A to critical articulated trains. Now in the present article, the authors have extended those analyses to critical conventional and regular trains as well. This is an important aspect because HSLM-A as such is an articulated-type model, so it is of interest to understand how it deals with covering the various resonance phenomena generated by other train types. Therefore, the main goal of this work is to establish whether the conventional and regular trains that stem from the validity rules given in Annex E/EN 1991-2, produce vibratory effects that are duly covered by HSLM-A. Following the aforementioned validity rules, one first aspect analysed is the importance of near-to-integer wheelbase ratios in the coupled vibrations produced by conventional trains. Subsequently, seven realistic, conventional and regular high-speed train models have been synthesised; these models have been made publicly available in Mendeley Data, and comprise almost 3800 different sequences of axle loads. Finally, the response of simply-supported bridges has been analysed with a view to compare the seven synthesised models versus HSLM-A. The exceedance and required speed increase have been computed for both displacements and accelerations, in a comprehensive ensemble of spans and speeds. The results provide a diagnosis of the degree of coverage of HSLM-A with respect to those conventional and regular trains compliant with Annex E/EN 1991-2. [ABSTRACT FROM AUTHOR]

With the increase in running speed, the aerodynamic characteristics of high-speed trains have a significant impact on running stability, energy consumption and passenger comfort. Since the shape of the high-speed train head can directly influence the surrounding airflow, optimizing the head shape is the primary way to improve the aerodynamic performance of the train. This paper reviews current research studies on the surrogate-based aerodynamic shape optimization of high-speed train heads, aiming to provide a comprehensive reference for designers to enhance design efficiency and optimization performance. The entire optimization process is divided into four essential steps, and the key optimization technologies in each step are discussed, including parametric modeling, computational fluid dynamics (CFD) simulation, surrogate model and optimization algorithm. By introducing the practical applications of these technologies, we summarize their advantages and disadvantages and suggest four potential research directions for the future. [ABSTRACT FROM AUTHOR]

Wheel-rail geometric parameters are crucial for determining wheel wear in high-speed trains. Under the action of a wheel-rail load, both the wheel and rail suffer elastic deformation, which affects the wheel-rail contact relationship and further influences the wheel profile and its evolution. In this study, a field test was conducted on a high-speed train operating at 250 km/h, and the worn wheel profiles and wear curves were continuously measured for one reprofiling cycle. Subsequently, a vehicle dynamics model is built using a wheel wear prediction model based on the integrated USFD wear algorithm. In this model, the finite element model of the wheel-rail contact is considered. The wheel-rail geometric parameters are obtained by determining their elastic deformation through the finite element method, which considers the effect of three parameters: the track gauge, back-to-back space of the wheelset, and rail cant. After considering the wheel-rail elastic deformation, the track gauge decreases from 1435 to 1434.5 mm, the back-to-back space varies from 1353 to 1352.3 mm, and the rail cant changes from 1:40 to approximately 1:37. Finally, the simulation and experimental results are compared, revealing that the wheel-rail elastic deformation has a significant impact on the wheel wear after the vehicle travels 150,000 km. The wear depth and wheel-rail equivalent conicity after considering the elastic deformation are closer to the measured results. [ABSTRACT FROM AUTHOR]

Abstract The noise level of a high-speed train is a crucial indicator of its operational quality. A significant low-frequency interior noise, referred to as ‘38 Hz’ in this context, has been detected during the operation of high-speed trains. This notable noise primarily occurs in the train attendant’s cabin near the windshield area. In this study, we conducted a comprehensive full-scale test to investigate the preliminary cause behind this significant ‘38 Hz’ noise. Our investigation reveals that it is associated with aerodynamic noise originating from the windshield area. To identify the root cause of this ‘38 Hz’ noise in the windshield area, we established a computational fluid dynamics (CFD) based model for aerodynamic noise analysis. The causes were found to be related to both the size and opening of the windshield cavity. Simulation results demonstrate that closing the upper opening significantly reduces the volume of ‘38 Hz’ noise compared to the original outer windshield structure design. We verified and validated these findings through an extensive full-scale test, which showed that by implementing our proposed modified windshield structure, there was approximately 7 dB reduction in significant ‘38 Hz’ noise observed within the train attendant’s cabin near the windshield area.

Objective As the train operational speed increases, various braking methods become essential for ensuring high-speed train emergency safety braking. Wind resistance brakes, which complement wheel-rail adhesion brakes, have garnered extensive attention. The installation of wind resistance brake plates affects the train streamlined shape and can influence train operational safety under crosswind conditions. To ensure train operational safety and braking performance in high wind environments, it is necessary to thoroughly investigate the impact law of different brake plate configurations on train aerodynamic performance under crosswind conditions. Method Using three-dimensional, constant, incompressible Navier-Stokes equation and k-ε two-equation turbulence model, the influence of crosswind existence and varying brake plate heights on of high-speed train flow field and aerodynamic force are investigated. Result & Conclusion Simulation research results indicate that under crosswind conditions, the aerodynamic resistance on train carbody and brake plates increases along carbody direction, while the lateral force decreases. When the brake plate height increases from 0.5 m to 1 m, the proportion of brake plate resistance in overall resistance rises from 54.89% to 69.92%, with the maximum reaching 56 kN. The proportion of brake plate lateral force in overall lateral force is less than 1%, indicating that different brake plate heights have relatively little impact on train overall lateral force. The brake plates have a certain stopping effect on the incoming flow, and there is flow field interference between closely spaced brake plates. The influence of brake plates on lateral forces is minor. With proper preliminary design of brake plates, wind resistance brakes can be an effective train braking solution with minimal impact on train operational stability.

Carbon fibre reinforced silicon carbide (C/C-SiC) composite materials have attracted increasing attention in brake system of high-speed trains, due to their low density, high specific strength, thermal stability, and frictional wear performance. This study aims to explore the mechanical properties of the 2.5D C/C-SiC composites, in order to characterise its potential application to the friction braking system of high-speed trains. To comprehensively evaluate the mechanical performance of the 2.5D C/C-SiC composites, the chemical vapor infiltration (CVI) method was adopted to prepare novel samples with high densification and low content of residual Si. The mechanical properties and failure mechanisms of the composites were investigated under various loading conditions, including tension, compression, bending, and shear tests. The experimental results indicated that the 2.5D C/C-SiC composites exhibited superior mechanical properties, with average in-plane tensile strength, compressive strength, bending strength, and interlaminar shear strength reaching 127.67 MPa, 326.92 MPa, 355.74 MPa, and 9.77 MPa, respectively, which are 2–8 times higher than the mechanical properties of C/C-SiC composites in existing publications. Under different loading conditions, the composites demonstrated characteristics of ductile fracture, pseudo-plastic compression fracture, pseudo-plastic bending fracture, and brittle shear fracture. Both high fibre content and the formation of SiC structure were advantageous for enhancing the load-bearing performance of C/C-SiC composites. The outstanding mechanical properties of the 2.5D C/C-SiC composite render the brake disc highly resistant to deformation and cracking under high stress, thereby enhancing its durability and establishing it as the ideal material for the next generation of high-speed train brake discs.

High-speed trains typically utilize helical gear transmissions, which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings. This paper focuses on the gearbox bearings, establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains. The modeling particularly emphasizes the precision of the bearings at the gearbox's pinion and gear wheels. Using this model, a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions. The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear, and this imbalance intensifies with the increase in train speed. Consequently, this results in a significant increase in contact stress on the bearings on one side. The adoption of herringbone gear transmission effectively suppresses axial forces, resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings. The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings, thereby extending their service life. [ABSTRACT FROM AUTHOR]

The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measurement of the dynamic load distribution in the four rows of two axlebox bearings on a bogie wheelset of a high-speed train under polygonal wheel–rail excitation. The measurement employed an improved strain-based method to measure the dynamic radial load distribution of roller bearings. The four rows of two axlebox bearings on a wheelset exhibited different ranges of loaded zones and different means of distributed loads. Besides, the mean value and standard deviation of measured roller–raceway contact loads showed non-monotonic variations with the frequency of wheel–rail excitation. The fatigue life of the four bearing rows under polygonal wheel–rail excitation was quantitatively predicted by compiling the measured roller–raceway contact load spectra of the most loaded position and considering the load spectra as input. [ABSTRACT FROM AUTHOR]

The accurate assessment of running safety during earthquakes is of significant importance for ensuring the safety of railway lines. Currently, assessment methods based on a single index suffer from issues such as misjudgment of operational safety and difficulty in evaluating operational margin, making them unsuitable for assessing train safety during earthquakes. Therefore, in order to propose an effective evaluation method for the running safety of trains during earthquakes, this study employs three indexes, namely lateral displacement of the wheel–rail contact point, wheel unloading rate, and wheel lift, to describe the lateral and vertical contact states between the wheel and rail. The corresponding evolution characteristics of the wheel–rail contact states are determined, and the derailment forms under different frequency components of seismic motion are identified through dynamic numerical simulations of the train–track coupled system under sine excitation. The variations in the wheel–rail contact states during the transition from a safe state to the critical state of derailment are analyzed, thereby constructing the evolutionary path of train derailment and seismic derailment risk domain. Lastly, the wheel–rail contact and derailment states under seismic conditions are analyzed, thus verifying the effectiveness of the evaluation method for assessing running safety under earthquakes proposed in this study. The results indicate that the assessment method based on the derailment risk domain accurately and comprehensively reflects the wheel–rail contact states under seismic conditions. It successfully determines the forms of train derailment, the risk levels of derailment, and the evolutionary paths of derailment risk. [ABSTRACT FROM AUTHOR]

Abstract High-speed trains typically utilize helical gear transmissions, which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings. This paper focuses on the gearbox bearings, establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains. The modeling particularly emphasizes the precision of the bearings at the gearbox’s pinion and gear wheels. Using this model, a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions. The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear, and this imbalance intensifies with the increase in train speed. Consequently, this results in a significant increase in contact stress on the bearings on one side. The adoption of herringbone gear transmission effectively suppresses axial forces, resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings. The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings, thereby extending their service life.

Abstract The accurate assessment of running safety during earthquakes is of significant importance for ensuring the safety of railway lines. Currently, assessment methods based on a single index suffer from issues such as misjudgment of operational safety and difficulty in evaluating operational margin, making them unsuitable for assessing train safety during earthquakes. Therefore, in order to propose an effective evaluation method for the running safety of trains during earthquakes, this study employs three indexes, namely lateral displacement of the wheel–rail contact point, wheel unloading rate, and wheel lift, to describe the lateral and vertical contact states between the wheel and rail. The corresponding evolution characteristics of the wheel–rail contact states are determined, and the derailment forms under different frequency components of seismic motion are identified through dynamic numerical simulations of the train–track coupled system under sine excitation. The variations in the wheel–rail contact states during the transition from a safe state to the critical state of derailment are analyzed, thereby constructing the evolutionary path of train derailment and seismic derailment risk domain. Lastly, the wheel–rail contact and derailment states under seismic conditions are analyzed, thus verifying the effectiveness of the evaluation method for assessing running safety under earthquakes proposed in this study. The results indicate that the assessment method based on the derailment risk domain accurately and comprehensively reflects the wheel–rail contact states under seismic conditions. It successfully determines the forms of train derailment, the risk levels of derailment, and the evolutionary paths of derailment risk.

Abstract The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measurement of the dynamic load distribution in the four rows of two axlebox bearings on a bogie wheelset of a high-speed train under polygonal wheel–rail excitation. The measurement employed an improved strain-based method to measure the dynamic radial load distribution of roller bearings. The four rows of two axlebox bearings on a wheelset exhibited different ranges of loaded zones and different means of distributed loads. Besides, the mean value and standard deviation of measured roller–raceway contact loads showed non-monotonic variations with the frequency of wheel–rail excitation. The fatigue life of the four bearing rows under polygonal wheel–rail excitation was quantitatively predicted by compiling the measured roller–raceway contact load spectra of the most loaded position and considering the load spectra as input.

Abstract Hunting stability is an important performance criterion in railway vehicles. This study proposes an incorporation of a bio-inspired limb-like structure (LLS)-based nonlinear damping into the motor suspension system for traction units to improve the nonlinear critical speed and hunting stability of high-speed trains (HSTs). Initially, a vibration transmission analysis is conducted on a HST vehicle and a metro vehicle that suffered from hunting motion to explore the effect of different motor suspension systems from on-track tests. Subsequently, a simplified lateral dynamics model of an HST bogie is established to investigate the influence of the motor suspension on the bogie hunting behavior. The bifurcation analysis is applied to optimize the motor suspension parameters for high critical speed. Then, the nonlinear damping of the bio-inspired LLS, which has a positive correlation with the relative displacement, can further improve the modal damping of hunting motion and nonlinear critical speed compared with the linear motor suspension system. Furthermore, a comprehensive numerical model of a high-speed train, considering all nonlinearities, is established to investigate the influence of different types of motor suspension. The simulation results are well consistent with the theoretical analysis. The benefits of employing nonlinear damping of the bio-inspired LLS into the motor suspension of HSTs to enhance bogie hunting stability are thoroughly validated.

Objective Existing methods for high-speed train gearbox bearing monitoring and diagnosis in China often rely solely on temperature or vibration data. Rely solely on a single temperature data point may result in missing early fault information of key components, while only vibration data may struggle to support identification of faults under complex coupling conditions. Therefore, it is necessary to combine temperature and vibration data to develop a fault diagnosis method for gearbox bearings with temperature-vibration features. Method To determine the decomposition parameters of VMD (variational mode decomposition) method, a weighted kurtosis coefficient indicator is introduced. Combining LMD (local mean decomposition) and VMD methods, a new approach for processing raw vibration data and extracting fault features is proposed. Based on the improved VMD method, LLE (locally linear embedding) feature dimensionality reduction method, and BP (back-propagation) neural network, a method for temperature-vibration feature fusion in bearing fault diagnosis is proposed. Time-domain features and temperature features are used as inputs to establish the temperature-vibration feature fusion bearing fault diagnosis model. Using a high-speed train rolling bearing test bench, fault simulation tests are conducted on gearbox bearings of a certain type of high-speed EMU (electric multiple units) in China, and relevant vibration data are collected to validate the effectiveness and feasibility of proposed model. Result & Conclusion The proposed fault diagnosis method for gearbox bearings achieves an average identification accuracy of over 98% for normal state, outer ring fault, and rolling element fault.

Objective To achieve reliable control of traction and braking key systems in trains while suppressing the impact of communication delay on train control, a discrete RBF (radial basis function) adaptive robust sliding mode control (abbreviated as ARSMC) method is proposed for critical network systems in high-speed trains. Method The traction and braking network systems in high-speed trains are introduced. An ARSMC method considering fractional delay terms is designed, and its stability is analyzed. The proposed discrete RBF ARSMC method is jointly simulated and analyzed using configuration software on a testing platform. Result & Conclusion The delay in discrete systems is divided into integer and fractional terms. By fully considering the fractional delay terms, the sliding mode traction and braking force with delay compensation under discrete approximate law is derived. The unknown nonlinear function in which is accurately approximated using an RBF neural network with adaptive adjustment characteristics. To suppress strong disturbances encountered during train operation, the sliding mode traction and braking force based on disturbance observer is integrated into the model to enhance its disturbance rejection performance. The proposed discrete RBF ARSMC method demonstrates superior stability and responsiveness compared to other control methods, exhibiting more ideal delay compensation effect and robust performance.

Objective Wheel flat scars can exacerbate the vibration of train transmission gears. Therefore, it is necessary to study the impact of wheel flat scars on the vibrational dynamic characteristics of high-speed train transmission gears. Method Based on multi-body dynamics theory and transmission gear technical parameters of a certain high-speed train, a dynamic model of the entire high-speed train, including coupled helical gears in bending-torsional-axial direction and wheel flat scars, is constructed. For flat scars of different lengths, the dynamic characteristics of high-speed train transmission gears, the maximum contact stress between large and small gear contact surfaces, and gear transmission errors are calculated and analyzed. Result & Conclusion When the lengths of wheel flat scar range from 0 to 30 mm, the vibration acceleration of large and small gears in high-speed train increases insignificantly; when the above lengths range from 30 to 60 mm, the vibration acceleration increases sharply, and the maximum contact stress between large and small gears increases from 630 MPa to 1 250 MPa, doubling by 2.08 times. As the length of wheel flat scars increases, the dynamic gear transmission error shows an increasing trend. When the length is 0, the maximum value of gear dynamic transmission error is 9 μm，and when the length is 60 mm, the maximum gear dynamic transmission error is 72 μm, increasing by 8 times.

Next-generation high-speed trains are required to achieve higher speeds, enhanced safety, environmental friendliness, and cost-effectiveness. To meet these technical goals, reducing the structural weight to a certain extent is crucial. A standard seat has the following six components: a backrest, a seat cushion, two side and middle armrests, a rear pedal joined with front and rear tables, and a seat bracket. Among these components, the seat bracket, which connects the seat to the carriage, acts as the main load-bearing structure. In the current lightweight design of seat brackets in high-speed trains, the traditional approach is based on structural optimization techniques, often size or shape optimization, with the goal of achieving a desired global stiffness or local stress level, and the optimized structural configuration does not have the best performance under time-varied loads. Thus, it would show a conservative approach, inefficient material utilization, and difficulties in achieving an increasingly stringent lightweight design. On the one hand, the seat bracket’s main structure must have sufficient strength; on the other hand, the key components must not deform substantially under alternating loads because the work conditions under the operation are affected by the track and the application scenarios. Motivated by this, we propose a design and analysis method that integrates SIMP (solid isotropic microstructure with penalization) based topology optimization and direct method (DM) based parameter optimization techniques, where the former applies to the main structure and considers maximizing structural stiffness as a design objective with a prescribed volume fraction constraint and the latter applies to key components, that is, the L-shaped connector, and considers the shakedown limit as the design objective, where the corresponding parametric model is developed and the optimal result is obtained by the genetic algorithm (GA). Using this method, the main load-bearing pathway can be determined and geometric reconstruction design can be performed based on this pathway for the main structure. Compared with the original design, a weight reduction of 17% of the optimized assembled seat bracket is achieved for high-speed trains while ensuring that the mechanical performance meets the requirements. For DM-based parameter optimization design, the load-bearing capacity of the shakedown is increased by 7.8%, and structural efficiency is improved by 23%, with a 12.5% reduction in the material of the L-shaped connector. This study may provide valuable guidance for the lightweight design of similar structures under repeated variable loadings.

The initial compression wave induced by a 400 km/h high-speed train entering a tunnel in two cases (offset running and center running) is investigated by overset mesh technology. The governing equations of the IDDES model for three-dimensional, unsteady, compressible flow are employed. The meshing strategy and numerical algorithm are validated by moving model test data. The spatial and temporal distribution characteristics of the initial compression wave and the one-dimensional planar wave characteristics are analyzed. The results show that the compression waves undergo three stages: from an irregular spherical shape near the train to an oblique shape, and finally to a one-dimensional planar wave. The initial compression wave captured at the measurement points at a distance of 5Di (Di represents the equivalent diameter of the tunnel) from the tunnel portal has been fully characterized by one-dimensional features, which can provide a boundary input for the propagation of the initial compression wave towards the tunnel exit. Compared to the offset running case, the initial compression wave amplitude and pressure gradient amplitude induced by central running are reduced by 3.66% and 6.87%, respectively. [ABSTRACT FROM AUTHOR]

The development of high-speed trains has increased the demand for dynamic vehicle tests on roller rigs. This study presents a nonlinear multi-body dynamic model of a vehicle system running on a roller rig and an actual track. Dynamic tests for a high-speed vehicle were performed using a full-scale roller rig to validate the numerical model. The hunting stability characteristics of the vehicle were investigated by performing a comparative analysis of the roller rig tests and numerical simulations of the vehicle on roller rigs and tracks. The results indicate that the critical hunting speed of the vehicle on a roller rig is lower than that on a track, particularly under significantly high or low equivalent conicity and yaw damper failure conditions. The characteristics of the hunting stability, riding performance, and lateral acceleration of the bogie frame were comparable in both rig tests and line operations, exhibiting consistent trends under the normal operation of the suspension system with the wheel/rail matches existing within the ideal range of equivalent conicity. However, the lateral acceleration or lateral Sperling index of the carbody could better detect the carbody hunting under low equivalent conicities, particularly when the lateral acceleration of the bogie was not sufficiently effective. [ABSTRACT FROM AUTHOR]