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Impact vibration due to the train passage at the joint of tongue rail has been known to induce the fatigue fracture of the hinged lug of turnouts. The impact vibration is considered to be enhanced by the mismatch of rails, the gap between the tongue rail and the base plate, and the loss of the tightening force of the bolt at the joint plate. However, the detailed mechanism has been unrevealed since the direct observation of the joint during train passage is inaccessible. In this study, we first measure the displacements of the tongue rail at the joint during train passage using small-size cameras. We evaluate the turnout whose hinged lug was broken. Displacement measurements show that the heel of the tongue rail (close to the joint) moves vertically downward by 3.9 mm and the toe of the tongue rail moves vertically upward by 2.3 mm when the train passes through the joint. Finite element analysis reveals that the downward displacement of the heel is caused by the gap between the tongue rail and the base plate and the upward displacement of the toe is caused by the rotation of the tongue rail around the supporting base plate. Acceleration measurements show that two peaks of impact acceleration enlarge the acceleration amplitudes (4400–7500 m/s2). Finite element analysis reveals that the first and second peaks are caused by the collision between the tongue rail and the wheel and that between the tongue rail and the base plate, respectively. Our results indicate that the gap between the tongue rail and the base plate should be minimized in addition to the mismatch of rails to reduce the amplitude of the impact vibration.

This paper describes a consideration of the difference in wheel/rail tangential contact force characteristics between in running tests and in laboratory experiments. To improve the accuracy of vehicle dynamics analysis, it is important to obtain the relationship between the tangential contact force coefficient and the slip ratio under realistic conditions. Since these characteristics cannot be obtained by numerical analysis, running tests on commercial lines and laboratory experiments using a twin-disk rolling machine are carried out. On the other hand, under conditions of high slip ratios, these characteristics differ between cases where the tangential contact force coefficient between wheel/rail remains contact and cases where the tangential contact force coefficient decreases. In this study, focusing on the state of the coefficient of friction between wheel/rail, a 3D-MBD model which can simulate vehicle behavior during braking was constructed on the SIMPACK commercial software, and these different reasons and their relationships were discussed. The result clarified that the difference in these characteristics is due to whether the friction coefficient on the contact surface is constant or fluctuating during the measurement by numerical analysis. That is, the characteristics measured in laboratory experiments can be modeled by Kalker’s rolling contact theory with a constant friction coefficient, and the characteristics measured in running tests can be modeled by combining the characteristics obtained by the Kalker’s theory under the conditions of different friction coefficients at each running distance.

In general, the life of a rolling bearing is calculated as the total number of rotations until rolling fatigue occurs on the raceway. However, when rolling bearings are used under light loads and high rotational speeds, they are damaged not by rolling fatigue on the raceways but by cage wear due to lubrication life. In such cases, the conventional method for calculating the rolling bearing life is not applicable. Rolling bearings for traction motors of railway vehicles (hereafter referred to as traction motor bearings) are one example of this and are replaced primarily due to lubrication life. However, there is no practical way to calculate lubrication life and these rolling bearings are replaced empirically. The purpose of this paper is to obtain basic data to create a method for calculating lubrication life. Therefore, traction motor bearings were rotated under conditions like actual operating conditions to reproduce damage due to lubrication life. As a result, damage due to lubrication life could be reproduced, so the next step was to investigate the effect on lubrication life when the operating conditions of traction motor bearings were varied as parameters. The parameters considered were “bearing temperature”, “vibration acceleration”, and “grease mass”. As a result of these verifications, lubrication life decreased exponentially when the bearing temperature was increased. In addition, lubrication life decreased exponentially when vibration acceleration was increased. Furthermore, lubrication life increased logarithmically when the grease mass was increased. The effects of these verified parameters on lubrication life could all be formulated within this paper.

In recent years, condition monitoring technologies have been widely developed aiming at safer railway operation and maintenance cost reduction. Condition monitoring systems of railway for both from onboard and on track have been widely studied thanks to the recent development of sensors. Using equipped sensors on track, as an example of the bogie abnormality detection, the diagonal imbalance of wheel-load for four wheels in a bogie is closely related to the running safety on curve. If serious problem happens in the bogie frame, the diagonal imbalance may change, and wheel load reduction occurs. For these reasons, the monitoring of the diagonal imbalance from track has a potential usefulness. However, in our previous research, the measured imbalance can be varied even though the focused bogies run on the track under almost the same condition such as boarding rate, vehicle velocity and so on. If the cause of variation is clarified, the limit of abnormality detection accuracy can be clarified. Therefore, in this study, variation of the measurement of bogie’s diagonal wheel-load imbalance are investigated. Furthermore, factors that affect the variation of the measurement is investigated using MBD simulation.

This paper describes a method for continuously measuring the contact position between the wheel and rail using strain gauges. The authors investigated the relationship between the bridge output sensitivity rate and the change in the placement of strain gauges using the result of finite element analysis for the instrumented wheelset. It is noted that the bridge output sensitivity rate is defined as the bridge output change per unit distance of the contact position (load position). Based on the result, strain gauges position suitable for measuring contact position was identified. On the other hand, static load tests were conducted on the instrumented wheelset with strain gauges attached to measure contact forces (wheel load, lateral force, and tangential force) and positions, respectively. The test results were found to be generally consistent with the finite element analysis results, and it was also observed that the load position of each contact force influenced each bridge output. Finally, this paper proposes a method for calculating the contact position by solving a nonlinear equation. The calculation uses the results of the load tests and also wheel rotation angle, bridge outputs, wheel load, lateral force and tangential force which measured in running railway vehicle. Simulations were performed for various cases, and the contact positions were obtained stably and continuously. This suggests that the proposed method is reasonable and applicable to various situations.

Instrumented wheelsets are widely used in the railway industry for the purpose of measurement of the wheel-rail interaction forces, which are crucial factors in a running safety assessment. The lateral force, which is the lateral component of the wheel-rail interaction forces, is measured using strains induced by bending deformation of the wheel web in typical configuraions of instrumented wheelset. In addition to the use of bending deformation, the author has proposed a new configuration of instrumented wheelset which usitilizes shear strains of wheel web as a measure of lateral force. In these principles of lateral force measurement using bending or shear strains, the measurement accuracy descreases when a loading point of wheel load, which is the vertical component of wheel-rail interaction forces, is shifted laterally since the wheel load also induces the bending and shear strains. In this research, output characteristics of several types of bridge circuits, which are categolized as “axially-asymmetric bridge circuit,” are investigated for the purpose of reducing the influence of wheel load and improving the measurement accuracy of lateral force. Numerical investigations using a finite element method and experimental investigations are carried out and the results show that the axially-asymmetrization of the bridge circuits is effective to reduce the infuluence of wheel load.

In order to enhance the safety of passengers in the event of the railway accident, it is important to identify the risk to the passengers. The seated passengers have a risk of getting injured due to collision with seats in front of them. The severity of injury depends on the structure of the seat types. There are a lot of types of the seats, for example a rotating and reclining seat and a walkover seat. However, the study compared the injury risk between these seats have not been reported. The purpose of this study is to investigate the effect of seat types to passengers’ injury through a series of physical sled tests. The rotating and reclining seat for normal car and green car in express train, and the walkover seat in suburban train were used for a comparison in this research. The experiment results showed that the measures to the lower seat back are effective for reducing the severity of injury of passengers seated in the rotating and reclining seat, that the measures to the seating face are effective for reducing the severity of injury of passengers seated in the walkover seat, and that the design of the footrest are also important for the measures.

Instrumented wheelsets are widely used in the railway industry for the purpose of measurement of the wheel-rail interaction forces, which are crucial factors in a running safety assessment. Information on lateral contact position between wheel and rail is also an important factor when discussing the wheel-rail contact conditions, such as the friction coefficient at the contact point. However, it is difficult to measure the contact position by using ordinary instrumented wheelsets since they are specialized only for the measurement of interaction forces. Therefore, the authors have proposed a signal processing procedure to extract information of contact position from bridge circuits constructed for the measurement of the lateral forces between wheel and rail by using bending and shear strains of wheel webs in a previous work. The purpose of this paper is to develop an online processing system which implements the proposed signal processing procedure. The original procedure requires long computational time and is not suitable for an online processing. As the first step to develop the processing system, this paper proposes a faster algorithm of signal processing procedure based on frequency analysis for extracting information of contact position from instrumented wheelset at first. Using the faster algorithm, a multi-rate processing system was developed to acquire the strain data at a high frequency and to execute the signal processing at a low frequency. The performance of the developed system was evaluated with a single-wheelset roller-rig test.

Vertical vibrations in railway vehicles are not only induced by track irregularity but also affected by the rotation of wheelsets with small mass imbalance. It is known that the excitation force generated by the rotation of wheelsets is transmitted from bogies to car bodies through longitudinal connecting members such as traction devices and yaw dampers. In this research, we first investigated the influence of yaw dampers on the vertical car body vibration induced by the rotation of wheelsets. Roller rigs rotation tests were performed using a full-scale vehicle with/without yaw dampers. In cases where there was no yaw damper, the vertical vibration of the car body was lower than that of cases where yaw dampers were equipped. This result indicates that vibration transmissibility from bogies to car bodies via yaw dampers should be reduced. In order to suppress this vibration transmission, we developed two vibration reduction devices: a new mounting structure for yaw dampers having a moving beam, and displacement-dependent rubber bushes for yaw dampers. The results of roller rigs rotation tests show that the developed devices reduced the car-body vertical vibrations caused by the excitation forces via yaw dampers. Moreover, we conducted running tests on a commercial track, and the results show that the vertical car body vibrations were reduced by applying displacement-dependent rubber bushes for yaw dampers.

The aerodynamic characteristics of a conventional line pantograph in a crosswind were investigated by conducting large-eddy simulations (LESs). In a previous study, wind tunnel tests using a full-scale pantograph were performed at various attack angles of the crosswind to understand the lift force characteristics of a pantograph in crosswind conditions. These experiments revealed that the lift force increases significantly when the yaw angle is set to 56°; however, the mechanism of increment of the lift force has not been clarified. Therefore, the flow fields around the pantograph head were investigated. It was found that there are two main mechanisms: one is a stationary large-scale vortex generated on the upper surface of the pantograph head, and the other is a pressure increment on the lower surface of the pantograph head. In addition, LESs were conducted using modified pantograph head shapes to investigate methods for reducing the lift force of the pantograph head using the mechanisms above. Two changes to the pantograph head shape were considered: a diagonal cut on the lower surface of the pantograph head and opening sections on the upper and lower surfaces of the pantograph head. The former shape generates a negative pressure area under the pantograph head, while the latter attenuates the large-scale vortex on the upper surface of the pantograph head. Thus, they achieve lift reduction by different mechanisms and can be used together. The lift reduction rate reaches approximately 60% when both methods are used together, indicating that this is an effective lift force reduction method.

This paper describes a practical wheel/rail tangential contact force model for railway dynamics analysis under running in rainy conditions. In our previous studies, it was confirmed that experimental results of tangential contact force measurement are agree well with Kalker’s rolling contact theory under dry condition with low humidity around contact surfaces. Here, it can be considered that if the ambient humidity around the contact surface become high infinity, the contact surface is under wet lubrication conditions. On the basis of this assumption, in this study, a practical estimation model for characteristics of tangential contact force under running in rainy conditions is proposed by combining the relationship between the adhesive coefficient and velocity measured on running experiments using actual railway vehicles and Kalker’s linear rolling contact theory. Therefore, to verify the proposed model, the tangential contact force measurement experiment using a twin-disk rolling sliding machine was carried out. As a result, it is confirmed that estimated formulae based on the proposed model are well agreed with experimental results even under different velocity conditions, comparing the relationship between tangential contact force coefficient and slip ratio. From these verified results, the proposed model is considered to be a practical wheel/rail tangential contact force model for vehicle dynamics analysis under rain conditions, because the proposed model has the advantage of low calculation cost and can be easily applied to vehicle dynamics analysis based on multi-body dynamics theories.

Since the wear of front-rod bearings of railroad switches induce the switch failure, wear evaluation is indispensable. On the other hand, the various parts of railroad switches are adjusted so as to avoid derailment. For example, the attachment position of the adjustment nut of switch adjuster rod could enlarge the contact force between tongue rail and stock rail. The extension of front rod is also used to eliminate the gap between the toe of tongue rail and stock rail. In this paper, the bearing wear during the switching operation is estimated by multi-body dynamics simulation. The effects of the attachment position of adjustment nut and the extension of front rod are also evaluated. When the switch moves rightward, the driving force of electric point machine is transmitted to switch rod through switch adjuster rod. Then, the force is transmitted to right tongue rail through right switch rod bracket which connects switch rod and right tongue rail. Although the attachment position of adjustment nut controls the contact force between tongue rail and stock rail, that does not change the path of force transmission and the force acting on the bearing. Therefore, the attachment position does not affect the bearing wear. On the other hand, the extension of front rod changes the path of force transmission. The most of driving force of electric point machine is transmitted to the left switch rod bracket, front rod and right tongue rail in order. Therefore, the increase in the force acting on the bearing increases its wear. In the case of 6 mm extension of front rod, the estimated amount of wear is 3.44 μm, which is 3 times larger than the case of no extension.

The critical wind speed of overturning is one of indices for the safety evaluations of railway vehicles against crosswind. The critical wind speed of overturning is defined as the wind speed when wheel loads on the upwind side becomes zero, and is often evaluated by the “RTRI’s detailed equation”. In the RTRI’s detailed equation, the lateral vibration inertia force of car bodies is considered as one of the acting forces affecting overturning. The inertia force can be obtained from the product of the lateral vibration acceleration and the mass, and the lateral vibration acceleration is assumed from past running test results. However, there are differences in position, direction and situation between the lateral vibration acceleration measured in the running tests and the lateral vibration acceleration in the calculation model of the RTRI’s detailed equation. In this paper, model experiments in a wind tunnel were conducted to clarify the effects of the differences with respect to the lateral vibration acceleration. Next, vehicle dynamics simulation was implemented to calculate the lateral vibration acceleration that occurs at the center of gravity of a car body under strong crosswinds. The results showed that the critical wind speed of overturning can be calculated accurately by using the simulation results of the lateral vibration acceleration that occurs at the center of gravity of the car body under strong crosswinds. In addition, a new method is proposed to estimate the lateral vibration acceleration using the track displacement data. Finally, when the critical wind speed of overturning was calculated assuming typical commuter vehicles, the wind speed obtained from the proposed new method was up to 2m/s higher than the wind speed obtained from the assumed equation in the RTRI’s detailed equation.

In the railway sector, efforts are being made to improve the efficiency of operations. One of these is the automatic operation of trains. To keep the train running safely, it is necessary to make sure that there are no obstacles in front of the railway vehicle. Therefore, automatic train operation requires obstacle detection system in front of the railway vehicle. In recent years, some railway operators have introduced onboard cameras as drive recorders in order to understand the situation at the time of an accident and to investigate the cause. In addition, efforts are being made in the railway sector to improve operational efficiency through the use of onboard cameras. In this paper, we propose an obstacle detection method using an onboard stereo camera. The proposed system can be divided into three parts. First, the center position of the track is estimated using RGB images, and the search area for obstacle detection is set. Second, proposed system checks for the presence of objects within the set search area and creates a candidate area of obstacle. Finally, the area of each neighboring candidate area of obstacle is calculated, and if the area is greater than a certain value, the object is determined to be an obstacle. Furthermore, the proposed system is verified by using a 1/10 scale model experimental vehicle. Validation results show that the proposed system is capable of detecting obstacles in front of railway vehicles.

To clarify the behavior of railway vehicles under crosswind, a new method using the left-right balance of air spring pressure is presented in this paper. The rate of off-loading, which is an evaluation index for vehicle behavior, can always be estimated by the new method without conventional special wheel-set. The method is theoretically derived and the accuracy is experimentally verified comparing the new method with the conventional method. In the experiment, lateral forces equivalent to crosswind were loaded statically or dynamically, and a running test was conducted. The results show that the new method and the conventional method are in good agreement and that the new method is useful when analyzing vehicle behavior under crosswind. By applying the practical method to the Shinkansen, it is possible to obtain statistical data on vehicles running at higher speeds or under higher wind speeds easily than with conventional methods. Much data was analyzed on the relationship between wind speed and the rate of off-loading, and the validity of the Kunieda’s equation used for vehicle design under crosswind is verified. This method can monitor effects of crosswind on vehicles not only at specific points but also along railway lines. Therefore, it is possible to identify areas where vehicles are likely to be affected by strong winds. Some examples further improve safety against strong winds are shown in this paper.

This paper describes the relationship between a tangential contact force and a slip ratio under various wet condition. In previous studies, the effect of difference in watering amount on the tangential contact force characteristics under wheel/rail contact condition has not been clarified quantitatively. In this study, to investigate the effects of various experimental condition such as circumferential velocity of a test wheel, the amount of water, and contact pressure on the tangential contact force characteristics, a tangential contact force measurement experiment was conducted under the condition of maximum circumferential velocity of 130km/h. As a result, if a small amount of water intervenes on the contact surface, we confirm that the tangential contact force under wet condition sharply becomes small about 30% or less of that under dry condition until the circumferential velocity increases to 30km/h; also, we confirm that the faster the circumferential velocity is the smaller the decrease in tangential force becomes. This tendency is the same under all contact pressure conditions and is qualitatively consistent with the actual phenomenon. Furthermore, to investigate the relationship of tangential contact force characteristics between on laboratory experiments and on test runs, we evaluated the relationship using Polach’ evaluation formula with wet model parameters and an adhesive coefficient planning formula. As a result, it is clarified that tangential contact force characteristics of wheels/rails under wet condition can be estimated on laboratory experiments by correctly evaluating a water film on the contact surface between actual wheels and rails.

Instrumented wheelsets are widely used in the railway industry for the purpose of measurement of the wheel-rail interaction forces, which are crucial factors in a running safety assessment. Information on lateral contact position between wheel and rail is also an important factor when discussing the wheel-rail contact condisions, such as the friction coefficient at the contact point. However, it is difficult to measure the contact position by using ordinary instrumented wheelsets since they are specialized only for the measurement of interaction forces. Although some configurations of the instrumneted wheelset have been proposed for the measurement of the contact position, those methods require some additional bridge circuits specilized for the contact position measurement. This paper proposes three types of signal processing procedure to extract the information of the contact position from a configuration of bridge circuits constructed for the measurement of the lateral forces between wheel and rail.

Currently, the maintenance of railway tracks is carried out based on track irregularity measurement data. The vibration data of running vehicles are easy to measure and can be the base of track maintenance, but they have not been used by basic data of track maintenance because of the shortage of repeatability. However, there are an increasing number of cases where small portable information terminals are used as simple and inexpensive vehicle vibration measuring devices. Therefore, the authors tried to construct the method for track management based on vehicle vibration data measured by permanently installed small terminals on in-service trains with high frequency. Data accumulation of vehicle vibration of in-service trains have been carried out for more than one year in a regional railway line. After the analysis of collected vibration data, the authors successfully conclude the possibility of the “vehicle-vibration-based track maintenance”. In this paper, the authors propose the method to obtain accurate positioning data of the trains from GPS speed data. The relationship between car-body vertical acceleration and track irregularity showed the possibility of track maintenance based on car-body vibration.

The aerodynamic forces acting on a train travelling in a tornado-like swirling flow were investigated using a tornado simulator and a moving model rig. Rectangular shaped vehicles in scale 1/40 and 1/67 and a round-roofed vehicle in scale 1/40 were used. Two types of tornado-like swirling flow, one-cell vortex and two-cell vortex, were generated by the tornado simulator. By changing the train speed and the train’s path, the model trains of 1 car composition and 3 car composition were passed through the swirling flow on a flat ground, and the aerodynamic forces acting on the vehicle were estimated. The main findings are as follows: 1) The aerodynamic forces acting on the leading car are greater than those of the other cars. 2) The aerodynamic forces of the leading car vary with the vehicle speed, but those of the middle vehicle show little dependence on the vehicle speed. 3) There is no significant difference in the aerodynamic forces acting on the train between a one-cell and a two-cell vortices. 4) The aerodynamic forces acting on the middle car increase when the train’s path is shifted by the core radius from the vortex center so that the flow becomes the headwind. 5) Rounding the roof of the vehicle may reduce the side force.

It is important to enhance the safety of the railway passengers on board in the event of a collision accident. The railway vehicle standard in European countries and the U.S. set the framework for structural crashworthiness design. On the other hand, an evaluation method for the crashworthiness design of railway vehicles has not been established yet in Japan. Our objective is to suggest the safety index for the railway vehicles in which longitudinal seats are arranged. The severity of passenger’s head injury was estimated in a level crossing accident scenario, including the horizontal collision position to a dump truck, the collision angle, the vertical collision position and the load weight of the dump truck by using numerical simulation. The correlation between the severity of injury of an Anthropomorphic Test Device (ATD) model and the safety index, integral of deceleration waveforms, mean deceleration waveforms and maximum waveforms which occurs on the railway vehicles at the time of collision with a dump truck were verified. It was found that the integral of deceleration values during an integration time timp had the highest correlation with the injury values of ATD. We suggested the integral of deceleration and the critical values of the second-furthest away from the bench-end partition as an evaluation method for the crashworthiness design of railway vehicles.

The crash safety structure of the railway vehicles is important as one of the safety measures against the train crews and the passengers in the event of a collision accident. It is impractical to perform collision testing many times using the actual train unit to design the crash safety structure, whereby the numerical simulation is effective and it is important to validate the analytical accuracy. However, there are few studies of collision tests and numerical simulations using actual size carbody structures according to Japanese design standards, and even fundamental data have not been sufficiently obtained. Therefore, firstly, the authors performed the collision test of an actual-size partial stainless-steel carbody structure of a railway leading vehicle against a rigid wall and finite element analysis under the same condition as the test for the purpose of validating and improving the analytical accuracy of numerical simulation. Secondly, we carried out the collision test of the same carbody structure of a railway leading vehicle against a typical large dump truck in Japan and obtained the fundamental data such as the time histories of the impact compression load and the acceleration of the carbody structure as well as the deformational and fractural behavior of them. We also performed FE analysis under the same condition as the experimental test and compared the numerical result to the experimental one. As a result, the numerical result was consistent with the experimental result. Finally, we expanded the partial carbody structure model to a single carbody model and carried out the collision analysis of it against a large dump truck. Thereby, the impact deformation and fracture behavior of the railway carbody under the actual level-crossing accident were estimated.

This paper presents a method for reducing vertical vibrations in a railway vehicle carbody by supporting underfloor equipment using high-damping elastic mounts. This is a kind of dynamic vibration absorber utilizing underfloor equipment as a mass element which has been introduced based on the inspiration of the damping effect of passengers. Numerical studies were firstly carried out to check the feasibility of the idea using simple two degree of freedom model representing carbody and underfloor equipment. Then a prototype of the elastic supporting member was built as a simple rubber mount and two type of excitation tests were conducted using a Shinkansen type test vehicle. The authors conducted excitation tests in the rolling stock testing plant to examine the carbody vibration reduction effect due to track irregularity. As a result, two dominant peaks in the acceleration power spectrum densities of floor corresponding to different elastic vibration modes were reduced simultaneously when the proposed method was applied. The vibration reduction effect became large as the elastically supported mass of underfloor increased. Then, to examine the vibration isolation performance of the developed rubber mount, excitation tests were conducted by a vibration exciter installed on the underfloor equipment. From the random wave excitation, the authors confirmed that the vertical vibration of carbody floor is reduced over a wide frequency band.

This study aims to establish a new restriction of ballast renewal works at a low temperature in winter. The authors construct a FEM model of railway track which simulates the ballast renewal work at a low temperature and perform the FEM analysis under the various conditions of track radius of curvatures R, length of ballast renewal work L and decrease in rail temperatures Δt. As a results, it becomes clear that the inward rail displacements and changes in axial rail forces increased with the decrease in R, and the increase in L and Δt. Based on FEM results, the authors propose the restriction diagrams of ballast renewal work which provide the allowable decrease in rail temperatures from the neutral temperatures of rail newly welded under the restriction of converted temperature of changes in rail forces, inward rail displacements and alignment defects due to inward displacements. Furthermore the authors propose the flow for users to judge propriety of ballast renewal work at a low temperature by use of the restriction diagrams. Consequently, the ballast renewal work at a low temperatures exceeding the current restriction can be executed.

It is generally known that the groove on tire tread can increase the friction force between the tire and the road surface under wet condition because of the improvement of drainage performance. Although wheel tread of actual railway rolling stocks have a wheel turning trace like the groove on tire tread, the characteristics of tangential contact force of the wheel/rail under wet condition is not clarified in detail. In this study, the tangential contact force measurement using a pair of small cylindrical specimens was carried out to investigate the relationship between the wheel turning trace and the friction force under wet condition. The experimental result shows the friction force under wet condition does not increase due to high iron’s stiffness if the wheel turning trace provided on the tread. On the other hand, it is also confirmed that the wheel turning trace has a reduction effect of the variation of the friction coefficient under wet condition. From the numerical analysis based on these experimental results, it is clarified that the longitudinal vibration of the vehicle can be decreased if the wheel has the wheel turning trace in case of the braking running under semi-wet condition.

Rail corrugation, which causes the vibration and the noise, is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and that there are three stages in the evolution process of the corrugation: formation, growth and saturation. In this paper, we analyze the dynamic characteristics of the track and vehicle in the saturation stage, propose a growth curve of corrugation, and verify them based on measured data obtained on commercial lines. As a result, it is confirmed that when the roughness amplitude grows and exceeds the critical roughness amplitude, there are two characteristics: the significant increase of the contact force fluctuation and the acceleration of the rail and wheel, formation of higher-order roughness components of the corrugation. The growth curve of the corrugation can be approximated by a logistic function.

In this study, a large-eddy simulation (LES) is conducted to investigate meandering airflows generated throughout the underbody of a real-shaped train model in open air. In our previous study, this was shown by an LES of airflows around a simplified train model. The shape of the underbody affects the flow. However, thus far, no systematic analyses that consider bogies have been conducted. Our experimental results qualitatively reproduced the power spectra of lateral velocity fluctuations in the underbody obtained using a 1:8.4-scale train model on a moving belt in a wind tunnel. Results on the effects of various bogie shapes suggested that the meandering flow was primarily affected by the time-averaged profile of streamwise velocity. Thus, the effects of the bogie shape on airflow are considerable. Comparing bogie shapes with and without a side cover, that without a side cover generated meandering airflow with a slightly smaller peak frequency than that with a side cover, and a completely smooth bogie generated no meandering airflows. It was confirmed that this LES was useful as a technical tool to develop measures to reduce meandering airflows around high-speed trains.

The variation in driving or braking force between the wheel and rail, which may cause longitudinal vibrations of the vehicle, sometimes causes reduction in adhesion and increases gliding. It is essential to elucidate the relationship between tractive force and longitudinal vibration in consideration of the electric and mechanical system in order to build a motor control method which can improve tractive force and reduce longitudinal vibration in the train set. In previous researches, numerical analysis methods for coupled motions in the vertical and longitudinal directions have been developed by introducing a sophisticated model of forces acting on the coupler. In the past, this analysis method has not been applied to the study of vehicle longitudinal vibration in a train. However, in recent years, the applicability to the analysis of vehicle longitudinal vibration has been studied, but it has not yet been fully studied. Therefore, in this report, the authors compare the test results with the numerical results when the fluctuating driving force is given to the numerical analysis model in order to confirm the effectiveness of numerical analysis. Furthermore, by using the numerical analysis, it is clarified that the frequency characteristics of the longitudinal vibration of the car body generated in the train due to the fluctuation of the driving force.

The coefficient of friction (COF) between the outer rail and the leading-outside wheel flange of a railway bogie running on sharp curved track is an important parameter for the progress of wheel/rail wear and running safety. Therefore, it is desired to grasp the actual state of COF of wheels especially at the leading-outside wheel flange. In the author’s previous studies, a roller-rig experiment was conducted with changing lubrication condition of each wheel of the bogie to figure out relationship between lubrication conditions and wheel/rail contact forces such as tangential, lateral and vertical directions. In this paper, a method to estimate the value of COF of leading-outside wheel with look-up tables built by repetitive numerical simulations is explained. In the construction of the look-up tables, friction coefficients for each wheel in the numerical simulation model are changed while collecting calculated wheel/rail contact forces. A railway bogie running on roller-rig test is considered for both numerical simulations and experiment with different lubrication condition, therefore look-up tables are built with a half-vehicle model running on the roller-rig. By inputting the wheel/rail contact forces measured in roller-rig test into the look-up tables built by simulations, and the COF of leading-outside wheel flange is estimated. The result shows that the lubrication condition of leading-outside wheel flange can be estimated by the proposed method especially when the value of COF is large and is useful for the detection of high COF condition.

This paper proposes a signal processing method to extract the longitudinal creep force from the strain signal that is acquired by an instrumented wheelset in a railway vehicle. The longitudinal creep force is an important physical quantity to discuss the wheel/rail contact condition and the curving performance. Although the instrumented wheelset can detect the longitudinal creep force by the use of the strain signals to measure the wheel load, a wheel rotation sensor such as a rotary encoder is needed to extract the quantitative force data in the conventional signal processing method. This paper proposes a novel signal processing method using the least square technique, which can extract the average value of the longitudinal creep force in a wheel rotation. The numerical tests using dummy signals show that the proposed method has similar frequency characteristics to the ordinary moving average filter in the region of frequency under 10 Hz when the wheel rotation speed is 20 rad/sec. It is also shown that the proposed method can extract the longitudinal creep force from the actual strain data acquired in the running test of real railway vehicle.

To clarify the mechanisms underlying airflow-induced vibrations of high-speed trains running through tunnels, large-eddy simulation of a large-scale flow structure around a simplified 6-car train model was conducted. Since actual trains run on one of the double track lines, the position of the train model was made to deviate from the tunnel center and hence the gap between one of the sides of the train and the tunnel wall is narrower than that of the other side. A train running in the open air was also calculated for comparison. The results of this study shed light on the generation mechanism of the pressure fluctuations acting on the side of high-speed trains as follows. Firstly, in the open air, the air velocity in the space between the underbody and the ground gradually decreases from the head toward the tail of the train. Thus, the air velocity is slower than that on both sides of the train, which generates shear flows near the bottom edges of both sides of the train. The shear flows cause large Karman vortex-like vortices (staggered Karman vortex street), which in turn lead to a meandering airflow beneath the underbody of the train. Secondly, in the tunnel, the air velocity not only in the gap between the underbody and the ground but also in the narrower gap between the side of the train and the tunnel wall gradually decreases from the head toward the tail of the train. In the same mechanism as the open air, a meandering airflow is generated throughout the side and underbody of the train and causes pressure fluctuations along the side of the train. Finally, it is demonstrated that the wavelength of pressure fluctuations along the side of the actual train can be estimated from the present LES results.

This paper proposes an identification method for transient characteristic parameters of the leveling valve, especially focusing on the leveling valve which has a dead zone of flow rate and the time delay on starting supply/exhaust operation. The transient characteristics of the leveling valve is crucial to discuss the quasi-static decrement in wheel load when a railway vehicle passes a transition curve. However, it is difficult to identify the transient characteristics through the conventional shaking test because of the time delay of operation. To identify the transient characteristics, this paper proposes a stationary test method which utilizes the “pneumatically controllable leveling rod” to acquire the step response of the leveling valve. This paper also proposes a parameter optimization method using the hybrid PSO/gradient method involving narrowing-down of the parameter definition area to solve the optimization problem for the transient characteristic parameters of the leveling valve, of which objective function contains highly nonlinear dynamics. The proposed identification method is verified through numerical experiments and real vehicle experiments.

In order to estimate the fatigue strength of used rail of railway, bending fatigue test of actual rail and plane bending of element specimen are conducted. In this paper, we discussed difference of results on each test methods from the viewpoint of fracture mechanics. Also, we proposed a simple method for estimating fatigue limit considering surface roughness of rust surface and residual stress. These results are as follows;(1) As a result of conducting bending fatigue test of actual rails, plane bending and uniform tensile fatigue test of element specimens, it was confirmed that respective fatigue strengths were different. (2) √ area and surface irregularities formed by rust on bottom of used rail were measured. As a result of estimating stress intensity factor with these parameters considering stress generated in each fatigue test, it was confirmed that the stress intensity factor differs depending on each fatigue test method, and that affects the fatigue strength. (3) It was shown that the difference in the dimensions of actual rail and element test piece affects the residual stress and size of corrosion hole existing in each test piece, which in turn affects the fatigue limit. (4) We proposed a simple method for predicting the fatigue limit of used rails, considering the residual stress and the estimation result of extreme value statistical analysis for maximum roughness Rz.

This paper describes the result of a tangential force measurement experiment by means of test wheels which is 500mm in diameter in order to investigate the relation between the size of the contact-patch and the tangential force characteristics. In the previous study on the tangential force characteristics of the wheel/rail, it had been sometimes indicated that the experimental results are a little bit smaller than those derived from the Kalker’s theory. Therefore, with a focus on the contact-patch of the wheel/rail, contact-patches of various sizes are set by means of changing the vertical load from 5kN to 35kN, and the tangential force coefficient and creep coefficient of contact-patch of various sizes are evaluated in terms of comparison with the Kalker’s theoretical value under the same criteria. As a result, we confirmed that the creep coefficient is 60% to 90% compared with the theoretical value under the same experimental conditions, because the ambient humidity of the test wheel is high and the contact-patch changes a little due to wear and plastic deformation. On the other hand, it has been clarified that the tangential force coefficient under large slip ratio condition in this study is saturated without falling like the Kalker’ theory.

This paper presents a basic study for developing a new adhesion improvement method for railway vehicles, focusing on the tangential force characteristics between wheels and rails. In our previous studies, the following phenomena have been confirmed. First, the tangential force of the wheel/rail is increased by repeated rolling and sliding frictional force, and the tangential force is stabilized by the oxide film covering the contact surface. In addition, the tangential force under the condition where the humidity around the contact surface is low tends to be larger than that under high humidity condition. And finally, these phenomena indicate that the friction coefficient of wheel/rail can be increased by instantaneously reducing the humidity around the contact surface. Therefore, in this paper, we propose a method for improving the frictional force that reflects the above-mentioned results in our previous studies. In the proposed method, assuming that it is applied to re-adhesion control of railway vehicles, the frictional force of the wheel/rail contact is temporarily increased by lowering the humidity around the contact surface by injecting dry nitrogen gas less than 30% humidity. To verify the proposed method, using a pair of the small cylindrical specimen, tangential force was measured under the conditions with different humidity. In addition, in order to confirm the effect on the braking performance of actual railway vehicle, numerical analysis was carried out. As a result, the experimental result showed the frictional force is increased by up to approximately 40% under high humidity condition, and it was confirmed by the numerical analysis that the proposed method has an improvement effect on the reduction of braking distance during dry nitrogen gas injection even if the humidity condition around the contact surface is high.

Rail corrugation that causes the vibration and the noise is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we verify three influence factors of the elastically supported beam model left as subjects in the previous paper. As a result of analyses, it is confirmed that when the track structure is usually used type, the effect of the rail axial force on the growth mechanism of the rail corrugation and the error compared with the analysis results by the model of the moving coordinate system are negligible, and the analysis by the elastically supported beam model is valid including at near the anti-resonance frequency of the elastic support track system.

The crash safety structure of the railway vehicles is effective as one of the safety measures against the train crews and the passengers in the event of a collision accident. The standards for crashworthiness of railway vehicles are defined in Europe and the U.S., while there are no standards for crash safety in Japan. Therefore, it is important to establish the evaluation method for crashworthiness of railway vehicles considering the actual situation of collision accidents in Japan. The authors carried out finite element analyses of a level crossing accident under various conditions (collision speed, mass of the obstacle and relative position between the train and the obstacle) based on the statistical analysis of serious level-crossing accidents in the past in Japan, and calculated the deceleration time histories in the passenger area under each condition. We evaluated these deceleration waveforms according to European and the U.S. standards for crashworthiness, and we also performed finite element analyses of dummy’s behavior and injury values using these deceleration waveforms as input. We verified the correlation between the evaluation results in terms of the deceleration according to these standards and dummy’s injury values obtained by finite element analyses. As a result, the evaluation according to the velocity at which a passenger contacts the seat back ahead of him (the U.S. standards) was the most effective. Moreover, the integrated values of the deceleration of the passenger area during an integration time t360 had the highest correlation with the dummy’s injury values.

The part of rail joint becomes the cause of the disadvantage points such as ride discomfort, undesired sound and track maintenance, etc. For restraining those points, the long rail made by welding the standard length rails has been developed. However, the problems of the buckling caused by the axial stress (i.e. the thermal stress which is brought out by the weather conditions or the friction heat between wheel and rail) of the rail have been pointed out. Therefore, some evaluation techniques for buckling management have been proposed. In this study, the relationship between the increase in compressive stress and the behaviors of the characteristics of the wavelet transform (i.e. a kind of time-frequency analysis) results of ultrasonic echoes was researched. The stress was increased in 10 [MPa] interval, and the echo at each stress was detected. From the results of experiment and analysis, it became clear that there is the relatively correlation between three characteristics and the stress. They are RMWC, RWE and RKTW respectively. The value of each RMWC, RWE and RKTW shows the ratio to the initial value (i.e. shows at 0[MPa] in this case) of MWC (i.e. the maximum wavelet coefficient), WE (i.e. wavelet energy) and KTW (i.e. the kurtosis of the time fluctuation waveform of the wavelet coefficient of the frequency that indicates MWC). Therefore, it was able to show the possibility of comparatively accurately predicting the increment of the stress by comparing the transitions of those.

The frictional force acts to the travelling pantograph head in horizontal direction due to sliding of the pantograph head and contact wire. Therefore, vertical motion of the pantograph head is generated by link mechanism of the pantograph. If the coefficient of friction between the pantograph head and contact wire is large, instability of the travelling pantograph could be observed. Although pantographs are modelled as lumped mass system and multi-body system, the unstable behavior of the travelling pantograph was not studied. This study proposes a 2-dimensional pantograph model that considers friction characteristics of the pantograph head based on the multi-body dynamics (MBD) approach. In this paper, a single-arm pantograph for shinkansen train is modelled using the MBD technique. Furthermore, a stability analysis method based on the complex eigenvalue analysis for the pantograph model is proposed. The equation of motion of the pantograph model is derived based on both the differential algebraic equation (DAE) and the linear dynamics equation (LDE). Results of the LDE-based stability analysis of the developed MBD pantograph models are shown. Then the obtained stability is validated based on the DAE-based time history response simulation of the pantograph models.

This paper presents the experimental results of the transient characteristics of the tangential force between small cylindrical specimens assumed as a wheel after re-profiling and a new rail respectively, generated in the case where the frictional force is applied to the wheel/rail contact surface repeatedly, and also the results of the numerical analysis of the influence of the wheel/rail contact surface properties on the running performance of the railway vehicles. In the experiments, the tangential force characteristics in case of sweep under the different longitudinal slip change rate conditions have been obtained by means of a twin-disk sliding-frictional rolling machine equipped with the environmental device in RTRI. The experimental results show that the tangential force coefficient is smaller in the range of a low longitudinal slip ratio compared with the Kalker’s theoretical characteristics that are obtained by applying the Levi-Chartet’s formula of saturation, which are the steady characteristics of the tangential force, in case of the contact surface close to that after re-profiling, and that the tangential force coefficient becomes large when the frictional force is applied to the wheel/rail contact surface repeatedly. This means that the coefficient of friction becomes large due to the repetition of the rolling and sliding friction. In addition, in order to investigate the relation between the contact surface properties and the running performance of the railway vehicle, a numerical analysis using a simple wheel-rail dynamic model was carried out by comparing Kalker’s theoretical value with the experimental values. As a result of the numerical analysis, it’s clarified that in case of the power running, the wheel after re-profiling is more slippery than that without re-profiling after long run in the range of a low longitudinal slip ratio.

Rail corrugation is such phenomenon that roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and cause the vibration and the noise. In the previous papers of ours, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we report the results of simulation analyses of the characteristics of each step of formation, growth and saturation of the rail corrugation using a discrete elastic support model close to the actual track. As a result of the simulation, the following are confirmed : (1) at the formation step, by providing a minute and irregular wheel load fluctuation, rail surface roughnesses are formed with such wavelengths that their amplification factor of roughness amplitude is maximal and greater than 1.0. (2) at the growth step, as the contact length of the wheel / rail becomes longer, growth of roughness of the short wavelength is suppressed. (3) at the saturation step, when the roughness amplitude increases and the wheel loses the contact with the rail, the growth is suppressed and the roughness amplitude saturates. Based on these results, we present the progress process of the rail corrugation and the ways to approach the countermeasures.

Rail corrugation is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and causes the vibration and the noise. Therefore, in this paper, we analyze the amplification factor of roughness amplitude using a model that takes into consideration the interaction between the track and the vehicle, and clarify the growth mechanism and the wavelength determination mechanism of the rail corrugation. As a result of the theoretical analyses, it is indicated that the essential factors of growth of the corrugation are (1) interference of rail wave motion between the front and the rear wheels of a bogie of the vehicle, (2) anti-resonance phenomenon of the elastic support of the track system, (3) anti-resonance phenomenon of the total system of the track and the vehicle, and (4) anti-resonance phenomenon of the vehicle system. In addition, as a result of examing the rail corrugation measured on the commercial lines, it is confirmed that the causes of the corrugation occurrence are the above mentioned (1),(2) and (3) factors, and that the measured wavelengths almost agree with the theoretical values.

When train passes through the rail joint at the heel of tongue rail of railroad switch, impact vibration is caused due to the step difference of the joint. This impact vibration is transmitted to the front rod, which is the attachment device located on the toe of tongue rail and connected with position checker device, induces the wear of bearing and leading to switching failure. Also, the wear of bearing of the special layout switch is more serious than that of the normal railroad switch because the special layout switch is more complex than the normal railroad switch. In order to clarify the mechanism of the wear, we measured the acceleration and axial force of the front rod of the special layout railroad switch in track open for traffic. Then, we have developed the finite element model of the special switch and validated the model by comparing with measured results. On the other hand, we calculated the coefficient of wear amount of bearing from wear test. Combining with the results of finite element analysis and the coefficient of wear amount, we predicted the wear amount of the front rod in the track. The wear amount of bearing of the special railroad switch is 10 to 20 times more than that of the normal railroad switch (Kondo et al., 2015). This is because the material of bearing of special switch is easier to wear than that of normal switch. Furthermore, the result is attributed to the structure of bearing of special switch. The axial constraint of bearing of special switch is weaker than that of normal switch, and so the bearing of special switch is easy to slide.

Human errors of train drivers may cause serious damage. Therefore, research on human error prevention has been conducted by many researchers. In this context, brain activity measurement of train drivers using Near-infrared Spectroscopy (NIRS) has been conducted to monitor the condition of train drivers. In this study, we developed a compact wireless wearable NIRS that can be used in natural environments. The wearable NIRS has been used to measure train drivers brain function using a train driving simulator. Experimental results showed that brain activity of DLPFC increased when the driver made braking operation. The experiment for train driving with an accidental event was carried out to evaluate the relation between driver's attention and the brain activity. As a result, there was a difference in brain activity between with and without prior notice. Results showed that the increased attention of the train driver can be appeared in NIRS signal from the outer part of prefrontal cortex.

The crash safety structure of the railway vehicles is effective as one of the safety measures against the train crews and the passengers in the event of a collision accident. However there is no standard for crash safety in Japan. In order to discuss guidelines for the crash safety design of the vehicle structure, it is important to grasp the actual situation of collision accidents in Japan. Therefore, firstly the authors performed the statistical analysis of serious level-crossing accidents for the past 30 years. Secondly, we carried out finite element analyses of a level crossing accident with a dump-truck under various conditions (collision position, collision angle, collision speed and mass of the load on the dump-truck) based on the result of the statistical analysis. We also evaluated their results in terms of the contact force, the deformation energy of the rail vehicle, the deformation amount of the cabin, the mean deceleration of passenger’s area (conformable to European standard), the maximum deceleration of the passenger’s area and the secondary impact velocity of the passenger (American standard). The degree of correlation among these results was discussed. The analyses showed that the horizontal collision position of the dump-truck and the collision speed had a comparatively large effect on the safety of passengers, and further that the mass of the load on the dump-truck also affected it when the secondary impact velocity was used as an evaluation index.

In railways, on-track running tests are implemented to assess running safety against flange climb derailment. Results of tests depend on the frequency component of measured data. In this paper, the relationship between the measured data of the derailment quotient, which is the assessment quantity of derailment, and wheel rise are investigated. The data for the investigation are obtained in a flange climb running test at low speed on a test track, which includes two sharp curves with cants. Several types of track irregularities, such as track twist, rail misalignment and angular bent at joints, are added to the test track, which are some of factors causing flange climb derailment. Some static wheel unloading is also set at the test vehicle's leading wheelset to induce flange climbing. We show that the derailment quotient data obtained through filter processing with some cutoff frequencies and the amount of wheel rise of the leading outer wheel have a similar tendency in time sequence, which indicates the usability of the filtered derailment quotient data for the assessment of flange climb derailment at low speed. Further, the cumulative value of the derailment quotient which is larger than the target maximum value is examined in order to evaluate the safety margin for derailment more precisely compared to the ordinary assessment by the derailment quotient only. As a result, we propose a new assessment quantity considering the cumulative value, and its target maximum value derived from the wheel rise and running distance.

It is important to secure running safety of railway vehicles against wheel-climb derailment accidents. The safety is often discussed according to the value of derailment coefficients for the leading outside wheel of a railway bogie running on sharp curves. Therefore, the detailed force induced mechanism which influences the value of derailment coefficients should be clarified. One of the most dominant factors affecting the value of derailment coefficients is magnitudes of the coefficient of friction (COF) between wheel and rail. Since the gauge corner of the outer rail and the top of the inner rail are lubricated at some sharp curves, COF of wheels of a bogie are different from each other and show complicated variation. In this study, the effect of lubrication for the running safety of the railway bogie is investigated while considering the detailed force induced mechanism of the derailment coefficient increase utilizing both multibody dynamics simulations and experiments. Experiments and simulations are conducted with a roller-rig test equipment under various conditions of wheel/rail lubrication. In this research, a method to identify whether the bogie is in suitably lubricated condition in terms of running safety is discussed. The proposed method making use of the longitudinal force measurement with mono-link type axle supporting device is mentioned.

It is pointed out that the yaw dampers, which are often installed in between carbody and bogie frame of a high-speed railway vehicle, have such unfavorable points that the damping force is generated not only in the yawing direction but also in other direction. As a result the damping force is generated also to the longitudinal or pitching vibration of a bogie, and the excitation force acts in the longitudinal direction of the carbody resulting in the increase of the carbody vibration of the longitudinal or vertical direction. In this research, to enable the reduction of the excitation of the carbody vibration while maintaining the original function of yaw dampers to prevent bogie hunting motion, a new mounting structure of yaw dampers on railway vehicles has been developed. The new mounting structure enables to reduce the excitation force transmitted from a bogie frame to a carbody through yaw dampers. In this paper, the effect of yaw dampers on the carbody vertical vibration is firstly shown based on the results of an excitation test of a full-scale vehicle, then the outline of the new mounting structure for yaw dampers and the design and manufacture of the prototype device are presented. The vehicle dynamics model based on multi body dynamics was constructed and the suppression effect of the yaw damper force generated to movement in the direction other than the yawing direction of a bogie was verified by the numerical simulation. Moreover, the prototype device was installed on a full-scale test vehicle and a bogie hunting motion test was carried out to verify the running stability.

It is important for railway bogies to get compatibility between curving performance and running stability. Utilizing independently rotating wheels may be an effective solution. The EEF bogie proposed by Dr.Frederich in late 1980th shows good curving performance making use of the gravity restoring force generated by the tread gradient of independently rotating wheels. However, the bogie gives rise to a kind of hunting motion as the vehicle running velocity increases. In this paper, an effective modification of the EEF bogie which solves the hunting motion is mentioned. The solution is to incline both wheel-axles while adjusting the tread shape of each wheel. In this paper, the EEF bogie with inclined wheel-axles is firstly proposed and analytically evaluated by the MBD simulation. Since the newly proposed bogie has complicated structures, a precise modeling of the bogie is mentioned in detail. From the result of eigenvalue analysis, proposed bogie can dramatically improve the hunting stability as compared to the conventional EEF bogie. In addition, the proposed bogie has excellent curving performance in tight curve section equivalent to the conventional EEF bogie. As those results, it is possible to achieve both high speed hunting stability and curving performance utilizing the proposed bogie unit in the vehicle.

Frictional heat is generated on the rubbing surface and various types of thermal localization occur during sliding contact in braking on disk and pad surfaces. Thermoelastic expansion affects the contact pressure distribution due to the frictional heat generation. The surface temperature is sometimes localized, and the thermal behavior causes surface damage. To evaluate this phenomenon, braking tests were conducted and the localized temperature on the disk surface was observed with an infrared camera. The localized temperature was found to correlate with frequency response for contact force variation. To investigate localized temperature on the disk surface, FEM analysis of the braking test was conducted. The FEM analysis method combined with contact analysis and heat transfer/thermal stress analysis was applied. Heat flux distributions were calculated by contact analysis in consideration of the frictional heating introducing the actual contact force and the friction coefficient variation. The disk surface temperature was then evaluated by the coupled heat transfer/thermal stress analysis using the heat flux distributions obtained from the results of contact analysis. The disk surface temperature obtained from FEM analysis almost coincided with that measured during the braking test. Moreover, the new method could greatly reduce the calculation time compared to the method using the contact analysis alone. Therefore, the proposed method is believed to be useful for evaluation of the rubbing surface temperature.

Fundamental study on a method to reduce the primary bending vibration for magnetically levitated (maglev) vehicles is conducted. These vehicles composed of lightweight car bodies are subject to elastic vibration; therefore, reduction of bending vibration will have considerable effect on ride comfort. First, a vehicle dynamics simulation model that can simulate bending car body is constructed to compare and analyze with the resonance characteristics of actual car body vibration in the field test. Then, this paper presents the optimal specification of the anchor, a coupling element between the car body and the bogie, to reduce the primary bending vibration. The validity of the calculation method of the specifications is verified by frequency response analysis, eigenvalue analysis, and vehicle dynamics simulation. Next, a test stand consisting of one-third segment car body to simulate the primary bending vibration is developed utilizing hardware-in-the-loop simulation (HILS). The results of swept sine excitation experiments confirm that the one-third car body can simulate the primary bending vibration of a full-scale car body with the HILS system. Finally, fundamental experiments are conducted in the test stand to reduce the primary bending vibration. The experimental results show that the optimally-designed anchor can reduce the primary bending vibration.