Yasushi Oka

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.

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%.

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.

Experimental and Theoretical Study on the Dynamic Performance of Steering Bogie in Sharp Curve

Abstract Bogie trucks for urban railway use are necessary to have not only excellent curving performance but also high speed hunting stability. From theoretical study, full scale stand test and commercial line run, we successfully created a new high-curving-performance bogie with optimized new tread profile. The design concept of new bogie, such as tread profile, suspension stiffness, etc., is described in the first part of this paper. Experimental and theoretical analysis of the comparison between the new bogie and conventional bogies are explained.

VERIFICATION OF DYNAMICS OF AN EXPERIMENTAL SINGLE-AXLE TRUCK - COMPARISON OF STAND TESTS, RUNNING TESTS AND SIMULATION

Abstract In order to reduce the cost of car construction, new style single-axle truck with high performance is developed. This truck was tested on rolling stand and on lield running. The test results were compared with theoretical analysis. All of the results agree well. In this report we describe the results of stand tests, running tests and numerical simulation on hunting stability and curving performance, and the comparison of there results.

DYNAMIC CHARACTERISTICS OF A SINGLE-AXLE TRUCK FOR COMPATIBILITY BETWEEN STABILITY AND CURVING PERFORMANCE

SUMMARY This paper presents the study on the vehicle with single-axle truck. The single-axle truck is expected as a truck for the new generation in especially commuter train and LRT. In this study, the authors focus on the compatibility between stability and curving performance in tight curve radius. The eigen value analysis and curving simulations using multibody dynamics software were made to examine the effect of the truck parameters such as secondary stiffness and characteristics of dampers. From these basic analyses trial test trucks were manufactured in the project of JREA. Stand tests were made to investigate the stability and curving performance. The test results showed suitable performance and some useful information was obtained according to the effect of truck parameters. After the small modification of the test truck, running tests were finally carried out in the commuter line. Although the oscillations of body were measured at the high speed range in straight track, up to 100 km/h running tests were successfully made. For the curving performance, it was found that the lateral force of the single axle truck was less than that of conventional two axle truck in the tight curve radius of 140 m. The estimated performance by theoretical studies were almost agreed with these experimental results. Consequently it was proved that the proposed design concept of the single axle truck was effective to the new generation truck design for commuter trains in Japan.

Effective Friction Control for Optimization of High Speed Rail Operations

Expected growth of High Speed Rail (HSR) in North America will in many instances involve operation on existing infrastructure, shared with other traffic. This will pose many challenges, not least of which will be wheel and rail wear, and ride quality. This paper addresses how effective friction control can be employed to mitigate these factors and provide an important tool to the designers of new systems. Case studies describe successful use of train mounted solid stick LCF flange lubrication on high speed trains in East Asia and Japan. In each case, higher speed train operation has involved operation on areas of track with greater curvature than usual on dedicated high speed track. Appropriately designed LCF systems provide an inherently very high level of reliability and very low flange wear rates. Use of dry thin film lubricant technology has advantages over use of liquid lubricants (oil and grease) which can experience splash and fling off at high train speeds. Train mounted solid sticks provide greater consistency / reliability and ease of maintenance compared with wayside gauge face lubrication. Complementing practical field experience, modeling studies are presented which show the potential of high performance flange lubrication to allow for additional flexibility in designing wheel profiles for high speed rail. The ideal profile will balance vehicle stability (benefiting from lower conicity) and curving performance (benefiting from higher conicity). In a high speed train with long wheel base and high suspension stiffness operating in areas with significant curvature, finding an appropriate compromise becomes even more challenging than usual. Controlling flange wear at low rates with highly effective solid stick lubrication offers the opportunity to use wheel profiles providing lower effective conicity and therefore better ride quality, without compromising wheel life. This approach will be practical only in a scenario where a very high reliability wheel / rail lubrication system is employed.Copyright