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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.

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. 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.

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 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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 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.

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.

A new vibration reduction device against flexural vibration of railway vehicle carbody utilizing deformation of a donut-shaped elastic body called elastic torus is presented in this paper. The vibration properties of the elastic torus specially designed and manifactured for rail vehicles are firstly presented, and simple one degree of freedom (1DOF) model and detailed finite element (FE) model of the elastic torus are developed. In order to check the vibration reduction effect by the elastic torus, a series of excitation tests using a Shinkansen-type test vehicle are conducted by applying up to 20 elastic tori. Large vibration reduction effect has been observed against flexural vibrations of the carbody, and multi-modal vibration reduction effect has also been demonstrated. Then, numerical studies using simple beam model applied with 1DOF torus model and detailed FE carbody and torus models are carried out to check the vibration reduction mechanism. It has been confirmed that the reduction mechanism by the elastic torus is due to the effect that the elastic torus act as dynamic vibration absorber. And it has also found that different elastic deformation modes of the torus lead to the multi-modal reduction effect.

The derailment coefficient is calculated from wheel-rail contact forces and it indicates the running safety of the railway vehicle especially in sharp curves. The derailment coefficient is affected by many factors such as the track irregularities, the vehicle parameters and the friction characteristics between wheel and rail. Therefore, monitoring of the derailment coefficient is desired to evaluate the running safety of the vehicle. Recently, a new monitoring bogie which can collect time series data of the derailment coefficient during commercial operation has been developed, and a large scale data is collected. However, there was no way to use such a data efficiently because an efficient method and an analysis tool have not been developed. In this research, a new analysis tool which can easily handle a large scale data and assist analysis of the derailment coefficient has been designed using MATLAB. In addition to measuring the derailment coefficient, the wheel load reduction and the track irregularity of twist are also measured. The tool can extract points where the derailment coefficient increases from a large scale data, and quickly show detailed information. On the basis of the information displayed on the user-interface, the data analyst can identify factors that increase the derailment coefficient. Not only analysis focused on a particular curve, but also the tool has the function for comparison of some curves. Analysis of the time change of the derailment coefficient is also possible. This paper shows the basic design of the analysis tool and gives some examples of analysis using this tool.

This paper presents a basic study to develop a new damping device against flexural vibration of railway vehicle carbody utilizing elastic deformation of an elastic body as a dynamic vibration absorber (DVA). A donut-shaped elastic body (called ”elastic torus” in this study) is proposed considering practical application to rail vehicles. Vibration measurement tests using some existing elastic tori are carried out to examine the effect by their size and infill upon natural frequency. In addition, excitation tests for a 1:5 scale model of a Shinkansen vehicle carbody are conducted, and the DVA effect by applying such elastic torus against the first mode of flexural vibration of the carbody is demonstrated. Then, numerical studies using finite element (FE) analysis are carried out and it has been found that the shape and the size of an elastic torus having desired natural frequency can be determined by the numerical model. Finally, an elastic torus dedicated as a DVA for rail vehicles made of rubber filled with water is designed using the FE model and manufactured actually.

This paper proposes a method to simulate the primary bending vibration in a test stand consisting of one-third segment car body and a full-scale bogie of magnetically levitated (maglev) vehicles. The purpose of this system is to evaluate an effect of high-frequency vibration to the ride comfort on maglev vehicles. The system utilizes hardware-in-the-loop simulation (HILS), which incorporates hardware components in the numerical simulation. A vehicle dynamics simulation model in the HILS system calculates internal forces acting from remaining two-thirds segment car body which is missing in reality, and applies constraint forces equivalent to the internal forces to the one-third segment using electric actuators. Fundamental studies on the proposed system were conducted. First, a new mathematical model, which can calculate the internal forces in low dimensions for real-time simulation, is presented. The validity of the model is verified with an eigenvalue analysis. Second, results of swept sine excitation experiments demonstrate that the actuators can perform immediate vibration responses with a new control method. Finally, fundamental experiments were conducted with the mathematical model and the control method to evaluate effects on vibration characteristics of one-third segment car body with exciting shearing force and bending moment at the body end. The results of these studies show the technical prospect of the test stand to evaluate the high-frequency vibration of maglev vehicles.

When a train travels through a tunnel at high speed, large pressure variations, which act on tunnel lining, equipments inside the tunnel, and the train, are generated in the tunnel. To predict these pressure variations, numerical simulations have been developed. Usually, one-dimensional simulations are used for such purposes. Although the pressure variations caused by the pressure waves can be calculated accurately by one-dimensional simulations, they can underestimate the pressure variations in the area very close to the passing train. The resulting accuracy can be increased by using computational fluid dynamics (CFD), but CFD requires high computational costs. Therefore, this paper proposes a three-dimensional but an efficient method to calculate accurately the pressure variation in the area very close to the passing train in the tunnel. It takes into account the distribution of cross-sectional areas of the train nose and treats the flow around the train nose as three-dimensional potential flow, and the upstream and downstream boundary conditions are specified by a one-dimensional simulation in order to calculate the effect of the pressure waves. The results by this method agree well with those of model experiments by using axisymmetric train model although the discrepancy to the model experiments by using actual shape train still remains.

Primary study on identifying deviations in the alignment of ground coils (ground coil irregularities) for magnetically levitated systems is conducted. The ultimate goal of this study is to introduce an active suspension system with preview in the future. First, the amount of irregular forces caused by twenty four types of ground coil irregularities is calculated respectively. The calculation results clarify that the irregular forces are complexly caused by various combinations of ground coil irregularities, and this shows that identifying ground coil irregularities by vibrations of the moving vehicles is appropriate toward the preview vibration control. Next, this paper refines an identifying method, which is originally developed for conventional wheel-on-rail systems, utilizing car body acceleration and Karman filter. To exclude a harmful influence originated by the spatial filter effects of onboard magnets, application of an impulse response of a particle model, instead of a rigid body model, and correction using the second order system compensational filter are proposed. Numerical simulation results show that the proposed method enhances the identification accuracy and widens the band of frequencies in which the irregularities can be identified. Finally, fundamental experiments are conducted in the test stand which can simulate vibrations of the moving vehicles in a range of frequencies sensitive to ride quality. The ground coil irregularities in the intended band of frequencies are experimentally identified with satisfactory accuracy by the proposed method, and the experiment technically enhanced the prospect of identifying the ground coil irregularities by car body acceleration.