Masuhisa Tanimoto

Formation mechanism and countermeasures of rail corrugation on curved track

Abstract From full-scale stand tests, commercial line experiments and numerical simulation, we found that corrugation of rail in curve section of track is formatted by stick–slip vibration between wheel and rail, which is caused by the large creepage and vertical force fluctuation on wheel/rail contact surface. On the basis of this theory, we analyzed the growing process of corrugation by numerical simulation.

Friction control between wheel and rail by means of on-board lubrication

The purpose of this study is to demonstrate the friction control between wheel and rail can solve wheel/rail contact problems, such as wheel-slipping, rail corrugation, squeak noises, wheel/rail wear and so on. Firstly, fundamental tests with two-roller-rigs were carried out to evaluate the friction performances of several types of friction modifiers. Then, for the purpose of realizing the friction control with them, authors developed an on-board system, which sprayed friction modifier from a bogie to the top of rail accurately. This method is very advantageous to control friction between wheel and rail. As a result of track tests, it was found that one type of friction modifier, which had proper coefficient of friction (COF) and positive creep characteristics, was very effective to reduce the lateral force and the squeak noises.

Wheel-rail contact mechanics at full scale on the test stand

This paper reports on the measured wheel-rail creep force characteristics and the mechanism of corrugation formation by using a full-scale bogie on a test stand. The measured creep characteristics agree well with the calculated values based on Kalkers linear theory. The relationship between creep characteristics and contact position is also discussed. The results show that a small change in wheelset lateral displacement may lead to a great change in creep characteristics. Mathematical models are developed in order to explain the mechanism of corrugation development. Simulation results agree well with practical phenomena. From the simulation results we find that the creep force characteristics and the vertical oscillation system have great influence on the formation mechanism of rail head corrugation.

Study on the Formation Mechanism of Rail Corrugation on Curved Track

SUMMARY Many researches on the problem of cormgation formatting on the track of railway have been reported in the world. But most of those researches are carried out by phenomena analyzing which occurred on real track or by just using theoretical model and scaled model simulation. For the reason of technical difficulties, theoretical researches proved by practical experiment are very rare. By using the cormgation formatting model considering with the characteristic of creep between wheel and rail interface we successfully fixed the formation mechanism of cormgation. Theoretical analyzing results agree well with the phenomena measured on stand experiment and on commercial line.

Creep force characteristics between rail and wheel on scaled model

Abstract In order to carry out the research project, which we call “Development of Intelligent Active Wheel,” a test facility of roller stand with 1/5 scaled truck is developed. Creep force characteristics between the roller rail and wheel at varied contact conditions are measured. From the measured results it is found that, in clean contact condition, creep force characteristics become negative as the creep rate becomes larger than 0.7%. In friction modifier high positive friction (HPF) applying condition, creep force characteristics do not show any negative property even if the creep rate increases up to 1.2%. The maximum F / Q , which is considered as friction coefficient at clean condition, is about 0.46, and the rate is about 0.16 at HPF applying condition as the creep rate increasing to about 1.2%.

Continuous observation of wheel/rail contact forces in curved track and theoretical considerations

By using non-contact gap sensors equipped on non-rotating parts of a bogie, a new measuring method of wheel/rail contact forces has been developed. The developed system has been verified to have sufficient durability for continuous measurement on in-service trains and sufficient practical accuracy after various stand tests and train running tests. After a long-period of continuous measurement on a commercial subway line, some important characteristics of wheel/rail contact mechanics were found by the analysis of measured data. Numerical simulations of curving with a full vehicle model using multi-body dynamics software were carried out, and according to the comparison with measured data, simulation results agree well with measured data in the steady-state values of derailment coefficients considering friction coefficient.

Curving performance evaluation for active-bogie-steering bogie with multibody dynamics simulation and experiment on test stand

The authors propose a new concept of the active steering bogie, which has simple mechanism and high curving performance. Active-bogie-steering bogie has the steering mechanism only between car-body and bogie frame and no mechanism in wheelsets. On curved track, the bogie frames are steered towards radial steering direction by actuators according to active control law. In this paper, we show that the lateral contact force of the leading-outside wheel can be reduced to zero even on very sharp curve by this mechanism. Validity tests were carried out by using a full-size test bogie on the rolling test stand, which can simulate curve-running condition. Bogie parameters and steering actuator characteristics are identified in order to compare the experimental results with multibody dynamics simulation. After these stand tests and simulation, we successfully verified the effectiveness of the proposed bogie mechanism and control.

The Optimum Design of an Onboard Friction Control System Between Wheel and Rail in a Railway System for Improved Curving Negotiation

In the subway lines of Tokyo (Tokyo Metro), there are many tight curves that may cause squeal noise, excessive rail/wheel wear and rail corrugation. To solve these serious problems, an onboard friction control system with friction modifier has been developed by the authors and has been equipped on commercial trains as a trial. With this system, the balance between supply and consumption of friction modifier is very important. That is to say, in order to obtain the maximum effect of friction control steadily, it is natural that an appropriate quantity of friction modifier should be required. In this report, results of experiments with a two-roller-rig testing machine, and analysis of the observed data in commercial train tests are introduced. In addition, the authors considered the method to realize the appropriate balance between supply and consumption of friction modifier.

Study on curving performance of railway bogies by using full-scale stand test

High specific bogie rolling test facility that can simulate curving condition was developed in 1988. Until now, various kinds of experiments and tests were carried out on the facility. Those include the basic experiments of wheel/rail contact mechanism, such as creep characteristics, formation mechanism of rail corrugation, and improvement of curving performance by using friction modifier. The curving performance tests of newly developed bogies were carried out on this facility, and some of those have been already realized on commercial lines. The results of experiments and tests on this test facility are verified for agreement with the results of numerical simulations and train running tests on commercial lines.

Correlation between Effects of Friction Control and Quantity of Supply

Controlling the friction between wheel and rail is direct and very effective measures to improve the curving performances of railway trucks, because the curving performances of truck depend much on friction characteristics. Authors have proposed a method, “friction control”, which utilizes friction modifier (KELTRACKTM HPF) with onboard spraying system. With the method, not only friction coefficient, but also friction characteristics are able to he controlled as expected. In this paper, results of fundamental experiments are reported which play an important role to realize the new method.