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The air spring for railway vehicles uses the air pressure inside the bellows to absorb vibration and shock to improve ride comfort and adjust the height of the underframe with a leveling valve to control stable driving of the train. This study developed augmented reality content that proposes a novel visual technology to effectively support the training of air spring maintenance tasks. In this study, a special effect algorithm that displays the dispersion and diffusion of fluid, and an algorithm that allows objects to be rotated at various angles, were proposed to increase the visual learning effect of fluid flow for maintenance. The FDG algorithm can increase the training effect by visualizing the leakage of air at a specific location when the air spring is damaged. In addition, the OAR algorithm allows an axisymmetric model, which is difficult to rotate by gestures, to be rotated at various angles, using a touch cube. Using these algorithms, maintenance personnel can effectively learn complex maintenance tasks. The UMUX and CSUQ surveys were conducted with 40 railway maintenance workers to evaluate the effectiveness of the developed educational content. The results showed that the UMUX, across 4 items, averaged as score of 81.56. Likewise, the CSUQ survey score, consisting of 19 questions in 4 categories, was very high, at 80.83. These results show that this AR content is usable for air spring maintenance and field training support. [ABSTRACT FROM AUTHOR]

Recently, research on condition-based maintenance (CBM) using artificial intelligence has attracted attention to reduce the maintenance costs of railway vehicles. The air compressor of a railway vehicle that adopts an air brake system is a target for CBM, and in order to reduce maintenance costs and ensure driving stability, technology to detect anomalies in the air compressor is necessary. The long short-term memory (LSTM) autoencoder is used to process sequence data. However, LSTM has limitations in that it cannot perform parallel processing due to its recurrent neural network characteristics, and it is difficult to learn the dependency between data as the sequence data lengthens. In this paper, we propose a novel transformer architecture as an anomaly detection model to learn dependency between air compressor data of a railway vehicle and we demonstrate superior data reconstruction and generalization ability of proposed transformer. We conduct simulation tests based on actual railway vehicle air compressor data and confirm improved anomaly detection performance. We propose an anomaly score definition method using mean squared error to perform reconstruction error-based anomaly detection. With the successful anomaly detection results in the air compressor of a railway vehicle, we demonstrate the effectiveness of a proposed anomaly detection algorithm that applies the moving average of anomaly scores and defines anomaly criteria using three-sigma. We test the proposed anomaly detection method using sensor data received from actual urban railway air compressors and prove its usefulness. [ABSTRACT FROM AUTHOR]

The significant accumulation of snow and ice in the bogie region severely compromises operational quality and poses a safety hazard to high-speed trains. To enhance testing capabilities for assessing ice and snow accumulation within bogie regions, this study conducts numerical investigations into the influence of contraction section configuration and deflector layout density on wind-snow flow quality within an ice and snow wind tunnel. The predictive accuracy of the numerical method is comprehensively validated against wind-snow wind tunnel tests, involving a comparison of airflow velocity in the test section and snow accumulation thickness on the channel's floor. The results demonstrate that the coupled numerical method of Improved Delayed Detached Eddy Simulation (IDDES) and Discrete Phase Model (DPM) is a reliable tool for analyzing wind-snow flow characteristics within an ice and snow wind tunnel. Furthermore, compared to the vickers curve and bicubic curve, quintic curves applied to the contraction section consistently compress and accelerate airflow. This contributes to a more uniform flow characterized by lower stream-wise fluctuation levels, pitch angles, and yaw angles in the test section, thereby significantly enhancing the overall flow quality of wind and snow. Thus, the quintic curves or smoother curves are recommended for the design of the contraction section in ice and snow wind tunnels. Moreover, increasing the deflector number leads to a noticeable improvement in flow quality inside the test section, while resulting in increased snow accretion on the windward surfaces of deflectors. Hence, a medium-level deflector density is suggested for designing ice and snow wind tunnels to achieve a better balance between flow quality and the additional snow accretion inside the channel. [ABSTRACT FROM AUTHOR]

Objective As a braking mode,electromechanical brake adopts the motor controlled screw rod drive to implement the pushing action, making the brake shoe to contact with the wheel and complete the transmission of brake force and friction brake. It is necessary to study the influence of the new brake mode on the vibration performance of rail transit vehicle. Method The basic structure and the composition of the electromechanical brake and air brake are introduced. The push-out stiffness test and track vibration test of the above two brakes are carried out and the influence of the brake push-out stiffness on vehicle vibration is analyzed. Result & Conclusion The stiffness test shows that the push-out stiffness of the electromechanical brake is much higher than that of the air brake in the normal working area and shows nonlinear characteristics, because it is driven by the motor and not equipped with stomatal piston as the air brake does. In line testing when the electromechanical brake is installed on the vehicle, it is found that compared with the air brake, the electromechanical brake will aggravate the vehicle brake vibration due to the large push-out stiffness, and the vibration acceleration of key components of the vehicle will also increase. Based on the research results, it is suggested that the push-out stiffness of the electromechanical brake shall be reduced to ensure smooth and safe brake processes for vehicles.

Modifying the car body structure from the existing train to another car body type requires an analysis of several factors. The strength of the design due to overload and the durability of the structures due to operational loads need to be re-evaluated. Furthermore, stiffness analysis also needs to determine the characteristics of the structure when it is not loaded. This study numerically analyzed the considerations in selecting the structural steel profile for modification of the existing car body into a panoramic type using the ANSYS Workbench R19. The underframe structure can still be used, and other structures are modified with the UNP profile. The side wall, and roof are changed in shape and size following the glass design of the panoramic train. The solid 3D model is rebuilt into a surface model to simplify the analysis. Static structural analysis is used to clarify the strength of the design under overload, a combination of static and transient structural analysis is applied to calculate the operating life, and modal analysis is chosen to figure out the stiffness. The simulation results showed that the modified design had met the needs and requirements based on the PM 175 standard of 2015 by the Indonesian Ministry of Transportation and the international standard EN-12663.

Track irregularities directly affect the quality and safety of railway vehicle operations. Quantitative detection and real-time monitoring of track irregularities are of great importance. However, due to the frequent variable vehicle speed, vehicle operation is a typical non-stationary process. The traditional signal analysis methods are unsuitable for non-stationary processes, making the quantitative detection of the wavelength and amplitude of track irregularities difficult. To solve the above problems, this paper proposes a quantitative detection method of track irregularities under non-stationary conditions with variable vehicle speed by order tracking analysis for the first time. Firstly, a simplified wheel–rail dynamic model is established to derive the quantitative relationship between the axle-box vertical vibration and the track vertical irregularities. Secondly, the Simpson double integration method is proposed to calculate the axle-box vertical displacement based on the axle-box vertical acceleration, and the process error is optimized. Thirdly, based on the order tracking analysis theory, the angular domain resampling is performed on the axle-box vertical displacement time-domain signal in combination with the wheel rotation speed signals, and the quantitative detection of the track irregularities is achieved. Finally, the proposed method is validated based on simulation and field test analysis cases. We provide theoretical support and method reference for the quantitative detection method of track irregularities. [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.)

This study investigates a new method for the effective application of active secondary suspension for reducing vertical vibration of the carbody to improve ride comfort of railway vehicles. So far, most previous control methods have contributed to reducing the vibration of the rigid body modes of the carbody at approximately 1 Hz or the first bending mode at approximately 10 Hz. However , in modern high-speed vehicles, higher frequency vibrations generally have a relatively greater influence on vertical ride comfort than vibrations of around 1–2 Hz. Focusing on this fact, the authors propose active secondary suspension with feedback control of the vertical vibration velocity of the bogie frame as a method for reducing carbody vibrations in a wide frequency band above 2 Hz to improve ride comfort. Numerical simulations were carried out to simulate the actual running of a Shinkansen using a vehicle model corresponding to a Shinkansen vehicle with 14 degrees of freedom, considering the vertical and longitudinal dynamics of the vehicle. The results show that this method is mainly effective in reducing vertical carbody vibration above 3 Hz and that the frequency band for vibration reduction can be extended to 1 Hz or lower by combining this method with feedback control of the vertical displacement of the bogie.

The gear transmission system is one of the essential subsystems of railway vehicles. The wheel polygonalization can affect the gear transmission system's condition monitoring and fault diagnosis, causing fatigue failure of the gear system and influencing driving safety. Therefore, to explore the mechanism of the wheel polygonalization in the gear system, this paper develops a Lagrangian form dynamic model of a railway vehicle with a gear transmission system. The model validation uses the data from the field test. The analysis explores the influence of the wheel polygonal fault on the gear transmission system under the traction condition. The results indicate that the wheel polygonal fault has amplitude/frequency modulation effects on the time/frequency response of the gear system. Also, the wheel polygonal fault causes the envelope of the speed curve to fluctuate periodically at a low frequency under traction conditions. The waveform asymmetry is gradually apparent as the traction continues. In the non-resonant region, the statistical analysis of the rotational speed fluctuation illustrates that the order of the wheel polygonal fault has more impact on the rotational speed fluctuation than the amplitude. Besides, in the resonance region, the eigenvalues of the system determine the magnitude of the amplitude. [ABSTRACT FROM AUTHOR]

The most general purpose of the current paper is to trace and discuss the history and state of the art of studies on vehicle motion (dynamics) in a transition curve above the critical velocity, with the aim of potentially increasing the circle of researchers involved in studying this issue and strengthening the will of the authors to continue their studies. This general goal is achieved in two ways: first, through a profiled literature analysis, showing the historical progress and current state of the research; and second, through reference to the history of stability studies as an example of selected studies' development. In addition, this work has two more specific goals. Together, they consist of collecting the literature in a related field in one place and analyzing it on site to accomplish the review. Both specific goals are attained by dividing the literature into two corresponding parts. In the first part, the current issues of rail vehicle stability are analyzed and divided into four problems. The second part includes works that deal with the subject of the motion and dynamics of a rail vehicle on a transition curve section. Here, the works are divided into five groups and discussed. They are put in order from the closest to the furthest from this paper's main subject; however, the last group includes the most recent references. In addition, information on the authors' approach to the problem is provided, including the methods and models used, as well as example results. Based on the analysis of the literature and the state of the art, a summary of the analysis is presented at this paper's end. It highlights the small number of works on the subject of interest, and based on the review of stability studies, it seeks to encourage present and potential authors to study this field and share their results with society. [ABSTRACT FROM AUTHOR]

To effectively implement condition-based maintenance for the air compressor in a railway vehicle, a thorough understanding of its fault characteristics and the collection of abnormal data is crucial. However, obtaining sufficient abnormal data from actual railway vehicles is challenging due to the rarity of air compressor failures in commercial railway services. This paper presents a detailed mathematical model of a two-stage piston air compressor that takes into account heat transfer effects. The mathematical model and the fault characteristics of the air compressor are analyzed through MATLAB simulation studies. The accuracy of the proposed model and analysis is verified by comparing it to real pressure data collected from a commercial Seoul subway train. The paper also generates abnormal data through simulations for specific fault conditions, including discharge valve leakages, air cooler malfunctions and pressure switch malfunctions. [ABSTRACT FROM AUTHOR]

The effects of structural nonlinearity (including rubber material and contact boundary nonlinearities) and variable wheel/rail contact point on the dynamic characteristics of resilient wheels are studied to investigate the mechanical properties of these wheels. Primarily, static and dynamic tests are designed to determine the nonlinear constitutive relationship of rubber materials in resilient wheels, and the viscoelastic properties of rubber are discussed. On this basis, the mapping relationship between the elastic modulus and stiffness of rubber in a resilient wheel system is deduced, and the stiffness characteristics of viscoelastic rubber materials are determined. The dynamic models of four types of wheels namely, a solid wheel (SW), a resilient wheel that considers linear rubber (RWL), a resilient wheel that considers nonlinear rubber (RWNL), and a resilient wheel that considers nonlinear rubber and contact boundary (RWNC), are established on the basis of the Yeoh constitutive model for hyper-elastic materials. The changes in wheel/rail contact point and wheel/rail force during train running are obtained under long/short wave irregularity excitation by adopting an established vehicle–track coupled dynamic model. Then the nonlinear dynamic behavior of resilient wheels subjected to varying wheel/rail contact point and wheel/rail force is studied. Finally, the influences of rubber material parameters on the dynamic characteristics of resilient wheels are explored. Results show that the acceleration of a resilient wheel is effectively reduced compared with that of SW. Resilient wheel acceleration that considers variable wheel/rail contact point is larger than that without considering the change in wheel/rail contact point. The deformation rates of rubber subjected to variable and constant wheel/rail contact behavior are 7 and 10%, respectively, and the midpoint deformation of rubber is less than its endpoint deformation. Compared with that of SW, the acceleration of RWL is reduced by 10 and 17% respectively under variable and constant wheel/rail contact points, respectively. Meanwhile, the acceleration of RWNL is reduced by 9 and 7% compared with that of RWL. The influences of nonlinear material characteristics and contact boundary on the dynamic characteristics of resilient wheels are not evident. The major vibration frequencies of the four types of wheels are 3–5, 10, and 22 Hz. The vibration and deformation of resilient wheels increase with an increase in the hardness of rubber. [ABSTRACT FROM AUTHOR]

A comprehensive modeling strategy for studying the thermomechanical tribological behaviors is proposed in this work. The wear degradation considering the influence of temperature (T) is predicted by Archard wear model with the help of the UMESHMOTION subroutine and arbitrary Lagrangian–Eulerian (ALE) remeshing technique. Adopting the proposed method, the thermomechanical tribological behaviors of railway vehicle disc brake system composed of forged steel brake disc and Cu-based powder metallurgy (PM) friction block are studied systematically. The effectiveness of the proposed methodology is validated by experimental test on a self-designed scaled brake test bench from the perspectives of interface temperature, wear degradation, friction noise and vibration, and contact status evolution. This work can provide an effective way for the investigation of thermomechanical tribological behaviors in the engineering field. [ABSTRACT FROM AUTHOR]

This paper describes a practical method for estimating the contact condition between wheel and rail using an instrumented wheelset in a railway vehicle. In a previous study, it was confirmed that an observer based on Kalman filter can estimate wheelset motion variables from measurement data of the instrumented wheelset using a single-wheel creep-force model. However, in the previous method, there is still a problem in that a precise value of friction coefficient between wheel and rail is required as a model parameter to estimate the wheelset motion variables with high accuracy. The accuracy of the value of friction coefficient affects the accuracy of estimation values since a single-wheel creep-force model refers to the creep force and the creepage. Moreover, the decision of the creep force heavily depends on the friction coefficient. To solve the problem, this study proposes a method to estimate the wheelset motion variables and the friction coefficient simultaneously by modifying the plant model. The estimation performance of the proposed method is verified by vehicle dynamics simulations and running test data. The verification results show that the proposed method is effective in estimating the friction coefficient when the track curve radius is smaller than or equal to 600m. In addition, the proposed method can improve the estimation accuracy of the wheelset motion variables compared to the previous method.

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

Although research has shown that through the additional rigidity introduced in the secondary suspension, traction rods can affect the vertical dynamic performance of railway vehicles, this topic has been less studied by researchers in the field. In this paper, the effect of a traction rod on the vertical vibration behavior of a carbody of a railway vehicle is analyzed, using the results obtained through numerical simulations. Numerical simulation applications are developed based on a vehicle model, where the vehicle carbody is modeled using a free-free equivalent beam Euler–Bernoulli, and the bogie chassis and wheelsets are represented by rigid bodies linked together by Kelvin-Voigt systems that model the secondary suspension and the primary suspension. The novelty element of this paper is found in the model of the traction rod. This includes traction rod damping, which has been neglected in previous research. The stiffness and damping of the traction rod are represented by a longitudinal Kelvin–Voigt system integrated into a secondary suspension model. The effect of the traction rod on the vertical vibration behavior of the vehicle carbody is analyzed based on the power spectral density of the acceleration, the root mean square of acceleration, and the ride comfort index, for three cases for analysis: a ‘without traction rod’ case, a ‘with traction rod—with damping’ case, and a ‘with traction rod—without damping’ case. The conclusions of the paper highlight the influence of the stiffness and damping of the traction rod on the vibration level of the carbody, especially in its middle. Depending on the stiffness of the traction rod, significant increases in the ride comfort index are obtained, which at high velocities can exceed 300%. Damping of the traction rod reduces the ride comfort index by up to 10%.

The air spring for railway vehicles uses the air pressure inside the bellows to absorb vibration and shock to improve ride comfort and adjust the height of the underframe with a leveling valve to control stable driving of the train. This study developed augmented reality content that proposes a novel visual technology to effectively support the training of air spring maintenance tasks. In this study, a special effect algorithm that displays the dispersion and diffusion of fluid, and an algorithm that allows objects to be rotated at various angles, were proposed to increase the visual learning effect of fluid flow for maintenance. The FDG algorithm can increase the training effect by visualizing the leakage of air at a specific location when the air spring is damaged. In addition, the OAR algorithm allows an axisymmetric model, which is difficult to rotate by gestures, to be rotated at various angles, using a touch cube. Using these algorithms, maintenance personnel can effectively learn complex maintenance tasks. The UMUX and CSUQ surveys were conducted with 40 railway maintenance workers to evaluate the effectiveness of the developed educational content. The results showed that the UMUX, across 4 items, averaged as score of 81.56. Likewise, the CSUQ survey score, consisting of 19 questions in 4 categories, was very high, at 80.83. These results show that this AR content is usable for air spring maintenance and field training support.

Although research has shown that through the additional rigidity introduced in the secondary suspension, traction rods can affect the vertical dynamic performance of railway vehicles, this topic has been less studied by researchers in the field. In this paper, the effect of a traction rod on the vertical vibration behavior of a carbody of a railway vehicle is analyzed, using the results obtained through numerical simulations. Numerical simulation applications are developed based on a vehicle model, where the vehicle carbody is modeled using a free-free equivalent beam Euler–Bernoulli, and the bogie chassis and wheelsets are represented by rigid bodies linked together by Kelvin-Voigt systems that model the secondary suspension and the primary suspension. The novelty element of this paper is found in the model of the traction rod. This includes traction rod damping, which has been neglected in previous research. The stiffness and damping of the traction rod are represented by a longitudinal Kelvin–Voigt system integrated into a secondary suspension model. The effect of the traction rod on the vertical vibration behavior of the vehicle carbody is analyzed based on the power spectral density of the acceleration, the root mean square of acceleration, and the ride comfort index, for three cases for analysis: a 'without traction rod' case, a 'with traction rod—with damping' case, and a 'with traction rod—without damping' case. The conclusions of the paper highlight the influence of the stiffness and damping of the traction rod on the vibration level of the carbody, especially in its middle. Depending on the stiffness of the traction rod, significant increases in the ride comfort index are obtained, which at high velocities can exceed 300%. Damping of the traction rod reduces the ride comfort index by up to 10%. [ABSTRACT FROM AUTHOR]

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

The dynamic behaviour and dynamic phenomena in traction drives of railway vehicle has been studied for decades. Generally, in these days the motivation for this research is to look for answers related with service problems, which has been risen, e.g. an overloading of mechanical components as wheelsets or an intention to improve control systems of traction drives of railway vehicles. This problematic has also motivated the research at the Faculty of Mechanical Engineering at the Czech Technical University (CTU) in Prague. Nowadays it is also usual, that the main research tool has been a simulation based on a mathematical model of a railway vehicle or its specific components, as testing on real vehicles is very demanding regarding costs. However, there is an alternative - a roller rig. At the CTU in Prague there has been modernized the second roller rig for purposes of measurement regarding the torsion dynamics research, to support PhD students for their theses and possibly to extend the education for students oriented on the railway vehicle's design. This contribution brings results of measurements just from the problematics of torsion oscillations and dynamics. Specifically, further presented measurements are on the loss of the adhesion in the contact of the wheelset and rollers, as the substitution for the railway, its impact on the reaction rod overloading and study of the axle load influence on the transition phenomena. [ABSTRACT FROM AUTHOR]

The interior noise characteristics of railway vehicles vary depending on the position of the cabin. In general, interior noises are louder in the area directly above bogies (ends of the cabin) than in the center of the cabin. It has been known that structure-borne sounds from bogies contribute greatly to the interior noises directly above bogies. This paper describes, using measured data obtained with the rolling stock test plant at Railway Technical Research Institute (RTRI), the application of the operational transfer path analysis (OTPA) to determine the contribution ratio of each transmission path of vibration from bogies to cabin floors. It is considered that structure-borne sounds from bogies propagate mainly through the parts connecting the bogie and car body such as single-link-type traction devices (traction links), yaw dampers, and air springs. As a result of applying the OTPA and determining the contribution ratios, it has been confirmed that the contribution ratios varied depending on the position of the floor and the frequency band. In addition, the validity of the contribution has been verified by examining the linearity of input/output data and the correlations of input data using multiple coherence functions and partial coherence functions. Although a bogie vibrates rigidly in the low frequency range with the very high correlation between the vibrations of the bogie and the parts connecting the bogie and car body, the correlation becomes low in the high frequency region. Therefore, it is expected that the contribution of each transfer path can be well estimated by applying the OTPA in the high frequency range for structure-borne sounds from bogies.

The evaluation of the vibration behavior of railway vehicle car bodies based on the results of numerical simulations requires the adoption of an appropriate theoretical model of the suspension which considers the important factors that influence the vibration level of the car body. In this paper, the influence of the secondary suspension model on the vertical vibration behavior of the railway vehicle car body is investigated, based on the results of numerical simulations on the frequency response functions of the acceleration, the power spectral density of the acceleration and the root mean square of the acceleration of the car body. Numerical simulation applications are developed based on a rigid-flexible coupled vehicle model with seven degrees of freedom, corresponding to car body vibration modes: bounce, pitch, and first vertical bending mode, and bogie vibration modes: bounce and pitch. Four different models of secondary suspension are integrated into the vehicle model, namely a reference model and four analysis models. Analysis models include systems through which the pitch vibration of the bogies is transmitted to the car body, influencing its vibration behavior and, respectively, a system that takes the relative angular displacement between the car body and the bogie and a system that models the transmission system of the longitudinal forces between the bogie and the car body are analyzed. The effects of these two systems on the vibration behavior of the railway vehicle car body are analyzed both for each system separately and together. In the conclusions of the paper, the influence of the secondary suspension model on the vibration level at the resonance frequencies of the vertical bending of the car body and the pitch of the bogie is pointed out. It also highlights the important contribution of the transmission system of the longitudinal forces between the bogie and the car body in transmitting pitch vibrations of the bogies to the car body, with effects on the vibration level of the car body at high speeds.

Track irregularities directly affect the quality and safety of railway vehicle operations. Quantitative detection and real-time monitoring of track irregularities are of great importance. However, due to the frequent variable vehicle speed, vehicle operation is a typical non-stationary process. The traditional signal analysis methods are unsuitable for non-stationary processes, making the quantitative detection of the wavelength and amplitude of track irregularities difficult. To solve the above problems, this paper proposes a quantitative detection method of track irregularities under non-stationary conditions with variable vehicle speed by order tracking analysis for the first time. Firstly, a simplified wheel–rail dynamic model is established to derive the quantitative relationship between the axle-box vertical vibration and the track vertical irregularities. Secondly, the Simpson double integration method is proposed to calculate the axle-box vertical displacement based on the axle-box vertical acceleration, and the process error is optimized. Thirdly, based on the order tracking analysis theory, the angular domain resampling is performed on the axle-box vertical displacement time-domain signal in combination with the wheel rotation speed signals, and the quantitative detection of the track irregularities is achieved. Finally, the proposed method is validated based on simulation and field test analysis cases. We provide theoretical support and method reference for the quantitative detection method of track irregularities.

Abstract A comprehensive modeling strategy for studying the thermomechanical tribological behaviors is proposed in this work. The wear degradation considering the influence of temperature (T) is predicted by Archard wear model with the help of the UMESHMOTION subroutine and arbitrary Lagrangian–Eulerian (ALE) remeshing technique. Adopting the proposed method, the thermomechanical tribological behaviors of railway vehicle disc brake system composed of forged steel brake disc and Cu-based powder metallurgy (PM) friction block are studied systematically. The effectiveness of the proposed methodology is validated by experimental test on a self-designed scaled brake test bench from the perspectives of interface temperature, wear degradation, friction noise and vibration, and contact status evolution. This work can provide an effective way for the investigation of thermomechanical tribological behaviors in the engineering field.

The dynamic behaviour and dynamic phenomena in traction drives of railway vehicle has been studied for decades. Generally, in these days the motivation for this research is to look for answers related with service problems, which has been risen, e.g. an overloading of mechanical components as wheelsets or an intention to improve control systems of traction drives of railway vehicles. This problematic has also motivated the research at the Faculty of Mechanical Engineering at the Czech Technical University (CTU) in Prague. Nowadays it is also usual, that the main research tool has been a simulation based on a mathematical model of a railway vehicle or its specific components, as testing on real vehicles is very demanding regarding costs. However, there is an alternative – a roller rig. At the CTU in Prague there has been modernized the second roller rig for purposes of measurement regarding the torsion dynamics research, to support PhD students for their theses and possibly to extend the education for students oriented on the railway vehicle’s design. This contribution brings results of measurements just from the problematics of torsion oscillations and dynamics. Specifically, further presented measurements are on the loss of the adhesion in the contact of the wheelset and rollers, as the substitution for the railway, its impact on the reaction rod overloading and study of the axle load influence on the transition phenomena.

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature 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 Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering 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.)

In order to ensure the secondary part at the front end of vehicles absorb the impact energy as much as possible in case of collision, reduce the impact on main parts, and ensure the safety of passengers and drivers, the energy absorption structure is set at the front end of the vehicle to improve the passive safety. Firstly, compared different standards at home and abroad and their requirements for collision conditions. Secondly, ASME RT-2 standard is selected as the standard, two energy absorbing structures are designed respectively. Structures mainly include head girders, corner posts and crash elements. The result shows that both structures can absorb more than 1.22 MJ of energy through the simulation by Ls-Dyna. At last, energy absorbing structures which has two energy absorb stages is tested to verify the reliability of the simulation results, and it is proved that the structure can meet the requirements of ASME RT-2.

The Brake operating unit (BOU) of a railway vehicle is one of the important systems for controlling the braking of the train. Because this system uses compressed air, it is difficult to understand and train the system. The existing education method involves learning the pneumatic flow of various control air in a 2D pneumatic circuit diagram based on a maintenance manual. However, in the actual braking system, it was difficult to learn effectively because the air flows in 3D. In order to solve these problems, the improvement of the training technique using the new 3D augmented reality (AR) was performed. In this study, to increase the learning effect of air brake flow, a technique for simultaneously displaying the pneumatic flow in 2D circuit diagram and 3D model was proposed. First, the distance ratio for simultaneous display can be determined using the proposed streamline matching variable calculation algorithm (SLMVC) that uses position and animation duration as input variables. Second, to avoid the complexity of using the 24 variables of the Particle System module in Unity, an existing universal 3D platform, a continuously emission property correction algorithm (CEPC) that can output particle objects as a streamline using only 4 properties (e.g., start lifetime, start speed, emission rate over time, start delay). As a result, the following 6 different types of BOU air pressure could be simultaneously displayed in 2D and 3D (e.g., AC, BC, SR, SBR, AS1, AS2). Therefore, maintenance staff can effectively learn complex pneumatic flow. To verify the usability of the developed content, a survey using the NASA-TLX technique was conducted targeting 60 maintenance staff. As a result of the comparison between Group A using the existing maintenance manual and Group B using the developed AR content, the perceived workload decreased by 28%. In particular, the frustration part decreased by 64% and the performance part decreased by 62%, indicating that the usability of AR content was very good.

The most general purpose of the current paper is to trace and discuss the history and state of the art of studies on vehicle motion (dynamics) in a transition curve above the critical velocity, with the aim of potentially increasing the circle of researchers involved in studying this issue and strengthening the will of the authors to continue their studies. This general goal is achieved in two ways: first, through a profiled literature analysis, showing the historical progress and current state of the research; and second, through reference to the history of stability studies as an example of selected studies’ development. In addition, this work has two more specific goals. Together, they consist of collecting the literature in a related field in one place and analyzing it on site to accomplish the review. Both specific goals are attained by dividing the literature into two corresponding parts. In the first part, the current issues of rail vehicle stability are analyzed and divided into four problems. The second part includes works that deal with the subject of the motion and dynamics of a rail vehicle on a transition curve section. Here, the works are divided into five groups and discussed. They are put in order from the closest to the furthest from this paper’s main subject; however, the last group includes the most recent references. In addition, information on the authors’ approach to the problem is provided, including the methods and models used, as well as example results. Based on the analysis of the literature and the state of the art, a summary of the analysis is presented at this paper’s end. It highlights the small number of works on the subject of interest, and based on the review of stability studies, it seeks to encourage present and potential authors to study this field and share their results with society.

The influence of braking sequence on railway brake disc's radial crack propagation behavior is analyzed considering the effect of crack geometry features, material elastoplasticity, and crack closure. The results show that when the residual stress generated in the initial braking is low, the peak stress in the subsequent braking will be low, and the average response state is more inclined to compression. The influences of the braking sequence are mainly reflected in the mid‐late stage of crack growth. In the early stage, the radial cracks almost synchronously expand inward and outward. While in the mid‐late stage, the cracks mainly expand inward. When the initial braking is relatively mild, the brake disc's stress–strain response and crack propagation behavior can be improved. It is beneficial to extend the brake disc's service life by designing a suitable prefabricated working condition or introducing an appropriate residual stress field through surface treatment. Highlights: The influence of crack closure on brake discs' crack propagation behavior is considered.The variation of crack propagation behavior in different service stages is discussed.The effect of braking sequence on brake discs' crack propagation behavior is studied.The proposal for the service life improvement of the railway brake discs is presented. [ABSTRACT FROM AUTHOR]

Gear tooth spalling is one of the inevitable fault modes in the long-term service of the traction transmission system of railway vehicles, which can worsen the dynamic load of the rotating mechanical system and reduce the operating quality. Therefore, it is necessary to study its fault mechanism to guide fault diagnosis scientifically. This paper established a planar railway vehicle model with a traction transmission system and an analytical time-varying meshing stiffness (TVMS) model of the spalling spur gear. Then, it analyzed the dynamic characteristics under traction conditions. The research found that the spalling length and depth affect the amplitude of the TVMS at the defect, while the width affects the range of the TVMS loss. The crest factor is the best evaluation indicator in ideal low-noise environments due to its sensitivity and linearity, but it is not good in strong-noise environments. Similarly, a time–frequency analysis tool cannot significantly detect the sideband characteristics that are excited by spalling. After high-pass filtering, the root mean square and variance exhibit excellent classification and vehicle speed independence in strong-noise environments. This research achievement can provide adequate theoretical support for feature selection and making strategies for fault diagnosis of railway vehicle gear systems. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic behaviour of a two-axle bogie under the influence of interference between the vertical vibrations of bounce and pitch—generated by the track irregularities—and the roll horizontal vibrations—excited by the asymmetry in the suspension damping that can be caused by the failure of a damper during exploitation. For this purpose, the results of numerical simulations are being used, as developed on the basis of two original models of the bogie-track system, namely the model of the bogie with symmetrical damping of the suspension—track and the model of the bogie with asymmetrical damping of the suspension—track, respectively. The dynamic behaviour of the bogie with symmetrical/asymmetrical damping is evaluated in five reference points of the bogie regime of vibrations, based on the Root Mean Square of acceleration (RMS acceleration). The results thus obtained highlight the characteristics regarding the symmetry/asymmetry of the regime of vibrations in the bogie reference points and the location of the critical point of the bogie regime of vibrations. The influence of the suspension asymmetry upon the dynamic behaviour of the bogie is analysed in an original manner, hence leading to conclusions that might establish themselves as the starting point of a new fault detection method of the dampers in the primary suspension of the railway vehicle.

Rubber material is widely used in railway vehicles due to its superior damping performance. The testing methods, fatigue, and aging theories of rubber materials are of great significance to improve the design, manufacture, and application of rubber components for railway vehicles. This work systematically introduces the constitutive theory, mechanical testing standards, and testing methods of rubber materials. Then, the aging mechanism is described and the research progress of rubber fatigue properties is reviewed from the perspectives of fatigue crack initiation and fatigue crack propagation. Moreover, the reinforcement methods of rubber materials are presented. Finally, according to the working conditions of rubber components in railway vehicle, the technical difficulties and future research trends of fatigue characteristics analysis of rubber materials and components are pointed out.

For the railway vehicle vertical dynamic model under the effect of damper rubber joint stiffness, there is no reliable and fast method to solve its dynamic response at present. In this paper, to improve the efficiency of numerical analysis, by reducing the degree of freedom of the system and transforming the vibration differential equation, a numerical solution method for railway vehicles vertical dynamic response under the effect of damper rubber joint stiffness is established. Through a case analysis, the variation of vertical random vibration response of railway vehicles with the stiffness of damping rubber joints is studied by using random vibration theory. This study provides an effective solution method for the numerical simulation of railway vehicles dynamic response under the effect of the damping rubber joint stiffness, and provides a guidance for the stiffness design of the damper rubber joints for railway vehicles. [ABSTRACT FROM AUTHOR]

In order to contribute to the reduction of CO2 emissions, rail vehicles are increasingly being equipped with alternative drives. Multi-system vehicles in particular are becoming very complex as a result. This results in elaborate testing as well as complex training for production, operation and maintenance. This publication is intended to contribute to the systematic and targeted development of new rail vehicles for passenger transport. Using model-based systems engineering and the modelling language SysML, harmonised requirements are documented, assigned to the new systems and targeted test cases are developed. Augmented reality experiences are then created to support the execution of the test cases during validation runs, commissioning and maintenance activities. The augmented reality experiences allow virtual information and the real environment to be linked and displayed on a mobile device. The aim of this publication is to present an end-to-end process that already takes the requirements of training into account during product development, so that it is easy to implement training using augmented reality technologies. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present applications and design elements of scale models of the carbody of railway vehicles integrated in experimental laboratory systems to verify the effectiveness of the methods to reduce vertical bending vibration of the carbody. In the first part of the paper, some applications of such experimental systems are presented, which include different scale models of the railway vehicle carbody. In the second part of the paper, the structure and dimensioning elements of a new demonstrative experimental system, specially designed by the authors of the present paper for testing the functionality of an original method of reducing the vertical bending vibrations of the carbody of railway vehicles, are presented. This method is based on an innovative approach that involves the use of a passive system consisting of two bars rigidly mounted on the longitudinal beams of the carbody underframe, having the role of opposing the bending of the carbody. The main element of the demonstrative experimental system is the scale model of the vehicle carbody, reduced to a beam, on which the two bars, called anti-bending bars, are mounted. For the dimensioning of the experimental model of the carbody and the anti-bending bars, original methodologies are developed in which several conditions are involved. In the case of the dimensioning of the experimental model of the carbody, the conditions refer to the convenient adoption of the scaling factor of the dimensions of the real carbody from the perspective of the practical realization of the experimental model of the carbody, ensuring the buckling stability of the demonstrative experimental system, achieving natural frequency of the vertical bending of the real carbody and avoiding the interference of the bounce vibration with the vertical bending vibration of the demonstrative experimental model of the carbody. The dimensions of the anti-bending bars are established from the condition that the vertical bending frequency of the experimental model of the carbody is outside the range of sensitivity of the human body to vertical vibration. Additionally, the natural frequency of the vertical bending vibration of the anti-bending bars must be chosen to avoid interference with the vertical bending vibration of the experimental model of the carbody. The effectiveness of the anti-bending bars in reducing the vertical bending vibration of the experimental model of the carbody is investigated with the help of numerical simulation results developed based on an original theoretical model of the experimental model of the carbody with anti-bending bars. [ABSTRACT FROM AUTHOR]

Many publications show that the ride comfort of a railway vehicle can be significantly improved using a semi-active damping control of the lateral secondary dampers. However, the control efficiency depends on the selection of the control algorithm and the damper dynamic behaviour, i.e., its force rise response time, force drop response time and force dynamic range. This paper examines the influence of these parameters of a magnetorheological (MR) damper on the efficiency of S/A control for several control algorithms. One new algorithm has been designed. Hardware-in-the-loop simulation with a real magnetorheological damper has been used to get close to reality. A key finding of this paper is that the highest efficiency of algorithms is not achieved with a minimal damper response time. Furthermore, the force drop response time has been more important than the force rise response time. The Acceleration Driven Damper Linear (ADD-L) algorithm achieves the highest efficiency. A reduction in vibration of 34% was achieved. [ABSTRACT FROM AUTHOR]

To effectively improve the estimated level of railway vehicles' vertical dynamic responses and provide a more suitable reference for the selection of its secondary suspension damping parameter, this paper has derived the root mean square values analytical formulae of the car body vertical acceleration, the secondary suspension vertical stroke, and the axle box vertical action force for railway vehicles under the random excitation of the track closer to the actual track characteristics. The correctness of the analytical formulae is verified by testing a real vehicle. Then, according to the analytical formulae derived, an analytical design method of the optimal damping ratio for the secondary suspension system is constructed based on the multi-objective programming and single-objective interval constraint analysis, which can be used to find the best trade-off for conflicting performance indices, such as ride comfort, running smoothness, and running safety and the influences of the system parameters on the optimal damping ratio are analysed. This research can effectively characterize the vertical vibration response of railway vehicles and provide an effective reference for the initial design of the railway vehicle secondary suspension damping parameter. [ABSTRACT FROM AUTHOR]

Abstract Running safety of the railway vehicles on the bridge during earthquakes is a major concern for railway engineering. To reduce the derailment risk of railway vehicles on bridges, friction pendulum bearings (FPB) are proposed to be equipped on simply supported bridges in this study. The full nonlinear behavior of the FPB is introduced into the vehicle-bridge interaction model. The effect of FPB’s manufacturing variations, including the shear pin’s strength and friction coefficient, on the misalignment was investigated. The manufacturing variations of the FPB were found to produce large lateral misalignment, which further contributes to large wheel-rail forces when the vehicle passes over the girder ends. It diminishes the improvement in the vehicle’s seismic safety provided by FPBs. Thus, a misalignment control device is proposed to limit the misalignment of the railway bridges equipped with FPBs. The vehicle-bridge interaction analysis results show that no wheel uplift occurred on the bridge equipped with FPBs and misalignment control devices during an earthquake. It indicates that the FPB significantly reduces the vehicle’s derailment risk on bridges compared with the non-isolated bearings.

Within the research of electromagnetically excited torsion oscillations in the mechanical part of traction drive systems of modern railway vehicles, which has been realized at the Faculty of mechanical engineering at the CTU in Prague, there are two separate simulation models in use. The basic calculation model, which is utilized to gain basic characteristics of the torsion system as natural frequencies and natural modes of oscillations. And the complex simulation model, which simulates a drive of the vehicle. This contribution is focused on the basic calculation model, which has been built in MATLAB. This model in its first version did not apply the contact between wheels and rails. It was necessary to find out, if this simplification is relevant with respect to subsequent simulations within the complex simulation model and its results. Therefore, the contact interaction as a traction force in longitudinal direction in the wheel-rail contact was realized via the Kalker’s linear theory. This article deals with the comparison between models with and without the implementation of the wheel-rail contact and its influence on the damping within the torsion system and retuning of the torsion system.

The implementation of temperature sensors represented by thermal imaging cameras is becoming increasingly rational. It is playing an important role in the socio-economic environment, in industry, scientific-research work. The main objective of the work is to assess the quality of the railway vehicles in exploitation and their thermal insulation, localise thermal bridges, and the tightness of the body using the FLIR-E6390 thermal inspection camera. An integration of test methods (research methods) was used including a diagnostic method based on a thermographic study integrated with the system approach method and system failure mode effects analysis (SFMEA). The scientific-research work included studies of seven types of railway vehicles in exploitation. A number of conclusions were reached. Specifically providing implementation of innovative and non-contact temperature distribution monitoring solutions for railway vehicles in a sustainability development system transport. Demonstrated the disparities between the different types of vehicles. Next, the identification of critical elements of their thermal insulation, the location of thermal bridges, and the tightness of the body of the rail vehicles, particularly the doors and inter-unit connections. The study covered the state of consumption of stationary electricity (for non-traction needs), implementing innovative indicators for stationary electricity consumption of railway vehicles as a new approach. [ABSTRACT FROM AUTHOR]

In terms of reliability, the damper represents the critical element of the suspension in the rail vehicle. A damper failure brings about a reduction in the damping of the suspension it belongs to, thus leading to the asymmetry of the suspension damping in the vehicle. The paper presents an analysis of the effect that the asymmetry of the secondary suspension damping has on the vertical vibration behaviour in the vehicle carbody and on the ride comfort, while using to that purpose the results derived from numerical simulations. The characteristics of the vibration behaviour for the resonance frequencies of the carbody dominant vertical modes are pointed out via the power spectral density of the carbody acceleration, which is weighted by the function of the sensitivity of the human body to the vertical vibrations. The ride comfort is assessed based on the ride index comfort calculated in three carbody reference points – at the centre and above the two bogies. [ABSTRACT FROM AUTHOR]

In this paper, the method and a control algorithm for detecting resonant destruction of a resonant auxiliary power supply for railway vehicle are proposed. It is essential to reduce the weight of the electric equipment attached to the lower part of the railway vehicle because it greatly affects the life of the railway vehicle, such as wheel and bearing. In order to reduce the weight and volume of the auxiliary power supply, in the case of windings, high-speed switching should be performed by lowering the input voltage. Therefore, in this paper, the auxiliary power supply control algorithm using an LLC resonant converter to reduce the weight of auxiliary power supply for railway vehicle is proposed, and the method of detecting resonant destruction due to device failure of a resonant converter is proposed. The proposed algorithm steps down the wire voltage using an input buck converter for high-speed switching, and the inverter input voltage is controlled through the LLC resonant converter. In addition, ZVS (Zero Voltage Switching) is operated to minimize the loss of the resonant converter, and the optimal design of the resonant tank is also proposed. In order to detect resonant destruction, a detection method formulated by analyzing the resonant current peak value for the load capacity is proposed. The algorithm proposed in this paper is verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

Rail corrugation is usually generated in modern railway transportations, such as high-speed railway, urban railway, and heavy-haul railway. It is one of the major excitations to the wheel--rail dynamic interaction, which will cause extra vibration and noise, failures, or even risk of derailment to the vehicle and its components. A dynamics model of a heavy-haul locomotive considering the traction power from the electric motor to the wheelset through gear transmission is employed to investigate the nonlinear dynamic responses of the locomotive. This dynamics model couples the motions of the vehicle, the track, and the gear transmission together. In this dynamics model, excitations from the rail corrugation, the nonlinear wheel--rail contact, the time-varying mesh stiffness, and the nonlinear gear backlash are considered. Then, numerical simulations are performed to reveal the dynamic responses of the locomotive. The calculated results indicate that different nonlinear phenomenon can be observed under the excitation of the rail corrugation with different amplitude and wavelength. The high frequency vibrations excited by the time-varying mesh stiffness are usually modulated by the low frequency vibrations caused by the rail corrugation. However, this is likely to vanish under the chaotic conditions with some corrugation wavelength. The vibration level of the vehicle and the gear transmission increases generally with the corrugation amplitude. However, some corrugation lengths have been found to be more responsible for the vibration of the dynamics system, which should be concerned greatly during the locomotive operation. Meanwhile, involvement of gear transmission systems will cause different dynamic responses between the wheelsets under rail corrugation and gear mesh excitations. [ABSTRACT FROM AUTHOR]

From a societal point of view, there are growing demands to increase traffic safety and reduce the risk of accidents of rail and road vehicles. The research to increase the safety of railway vehicles, which is carried out at the Faculty of Mechanical Engineering of the Czech Technical University in Prague, aims to increase the active and passive safety of railway vehicles. Components and systems of active safety are designed to reduce the risk of an accident. Components and systems of passive safety are designed to minimize the consequences of accidents. One of the parts of the active safety of railway vehicles is the condition and safety of the railway lines on which the railway vehicle is operated. The first part of the article focuses on the evaluation of accident statistics of railway vehicles with other road users at railway crossings for the years 2014 to 2018 with regard to the cause of the accident and the level of security of railway crossings. The conclusion of the article is devoted to proposals for solutions that could lead to a reduction in accidents at railway crossings. [ABSTRACT FROM AUTHOR]

Within the research of electromagnetically excited torsion oscillations in the mechanical part of traction drive systems of modern railway vehicles, which has been realized at the Faculty of mechanical engineering at the CTU in Prague, there are two separate simulation models in use. The basic calculation model, which is utilized to gain basic characteristics of the torsion system as natural frequencies and natural modes of oscillations. And the complex simulation model, which simulates a drive of the vehicle. This contribution is focused on the basic calculation model, which has been built in MATLAB. This model in its first version did not apply the contact between wheels and rails. It was necessary to find out, if this simplification is relevant with respect to subsequent simulations within the complex simulation model and its results. Therefore, the contact interaction as a traction force in longitudinal direction in the wheel-rail contact was realized via the Kalker's linear theory. This article deals with the comparison between models with and without the implementation of the wheel-rail contact and its influence on the damping within the torsion system and retuning of the torsion system. [ABSTRACT FROM AUTHOR]

The purpose of this study is to clarify the seasonal characteristics of the thermal sensation and comfort of occupants in a main line vehicle in Japan. In addition to the summer and winter experiments conducted in our previous research, we carried out the subjective experiments in the autumn and the spring. The participants rode a main line vehicle stationed at a rolling stock center, and they experienced the non-steady-state thermal environment ranging from around 20℃ to 30℃ and answered questionnaires about their thermal sensation and comfort. Based on the experimental results obtained in the four seasons, the seasonal characteristics of the relationships between the thermal indices called PMV/PPD and the subjective evaluation values were analyzed, and the seasonal differences in the prediction accuracy of PMV/PPD was also examined. The mean thermal sensation has strong correlation with the PMV in all seasons, and the seasonal differences in the relation between them were not found. Furthermore, the percentage of the participants who felt cold/hot sensation in all seasons got good agreement with the PPD. These results support the validity of PMV/PPD as the prediction indices for thermal sensation in railway vehicles. On the other hand, the seasonal differences were found in the relation between the PMV and the percentage of the participants who felt dissatisfied and the relation between the PMV and the percentage of the participants who felt sweaty – in the summer, the percentage of the participants who felt sweaty and dissatisfied was higher than in the other seasons. The root mean square errors of the PPD in the spring, summer, autumn and winter experiments were 12.9pt, 20.4pt, 17.8pt and 11.0pt, respectively. These results suggest, in order to use the PPD as a highly accurate indicator of thermal comfort in Japan all the year around, it should be corrected taking into account the seasonal characteristics of thermal comfort.

The importance of the railway transport of both goods and passengers continuously grows as it is in many points of view more ecological and economical solution in comparison with road transport. Just the importance has been supporting efforts to design more powerful and faster trains reaching traction powers more than 1.6 MW per a wheel-set or service top speed much more than 300 km/h till these days. To reach design which has enabled such a kind of performances it was necessary to research dynamic behaviour of railway vehicles. Both via laboratory measurements and simulations. The laboratory experiments have been carried out on a specially designed laboratory equipment called roller rigs. A laboratory equipped by roller rig for testing of the railway vehicle dynamic behaviour has been built at the Faculty of Mechanical Engineering at CTU in Prague, also within PhD study programs and SGS grants. Another powerful tool within research activities is a simulation. Kind of a such simulation will be presented by this contribution with the focus on the torsion dynamics of high-power fully-suspended drive of a railway vehicle, which has been developed also by PhD students under financial support of The Faculty of Mechanical Engineering and related grants.

Helical gears are commonly used in the gear units of railway vehicles in Japan, and the bearing types used for the gear units are tapered roller bearings. In this gear unit bearing arrangements, it is important to appropriately adjust the combined clearance, called the endplay, of the two bearings supporting the pinion to prevent the damage such as seizure. Our previous research has shown that the smaller the endplay value at gear unit assembly (Initial endplay value) and the lower the ambient temperature, the greater the decrease in endplay value during rotation and the greater the risk of seizure. One of method to prevent seizure is to increase the initial endplay value, but this means an increase in the internal clearance of the bearings, which may reduce the fatigue life of the bearings or cause damage to their cages due to increased vibration. In order to prevent seizure without reducing bearing life, therefore, this study has examined the use of cylindrical roller bearings with ribs that allow a certain degree of axial displacement of inner rings and outer rings, and has compared its performance with that of a conventional structure using tapered roller bearings through various rotating tests. As a result, it is found that the temperature rise immediately after the start of rotation and torque of pinion shaft are lower for the cylindrical roller bearings with ribs than for the tapered roller bearings during the rotation test using the actual gear unit. Further, the results of rotating tests under the radial and axial loads for the pinion bearings alone showed that the torque of cylindrical roller bearings with ribs tended to be lower than that of tapered roller bearings under a large range of flow rate and temperature of lubricants.