Computational Technology Resources - IJRT

Keywords: flange climb derailment, running-in, contact stiffness, real contact area, ultrasonic measurements.

Abstract

Flange climb derailment is most likely to occur during the wheel-rail running-in phase, such as just after the railway vehicle wheels have been re-profiled or during morning rush hour. It is thought that the underlying cause is an increase in traction due to changes in the contact between wheel and rail. However, the mechanism of this increase in traction remains a subject of continuing controversy. Active ultrasonic measurements have been effectively used to measure wheel-rail contact conditions, particularly the contact stiffness. In this study, the ultrasonic method is used to characterise the wheel-rail contact during running-in whilst the surface roughness of the wheel reduces due to cyclic loading against the rail. An array of sensors was mounted behind the wheel flange so as to reflect ultrasound directly from the contact. An initial investigation was carried out to understand the measurement resolution of this ultrasonic array transducer. A static measurement was then performed by traversing the ultrasonic array transducer across the wheel when statically loaded against the rail. Following this, the same array transducer was fixed to the wheel and dynamic measurements were carried out. These measurements were cyclic to investigate the effect on changing surface topography. From this, the relationship between the slip and the contact stiffness was investigated. It was found that an increase of contact stiffness was measurement after slip motion was recognized. Both the static and dynamic measurements showed a difference in the wheel-rail contact conditions. In the case of the rolling condition, the peak position of the contact stiffness in the contact area shifted from the centre of the contact to the exit side. From the cyclic rolling tests, it was observed that the change in surface topography resulted in an increase in interfacial contact stiffness. This phenomenon indicates that there is an increase in real area of contact between the wheel flange and the rail gauge corner during running-in.

download the full-text of this paper (PDF, 20 pages, 6612 Kb)

go to the previous paper
go to the next paper
return to the table of contents
return to IJRT
purchase this issue (price £80 +P&P)

	Computational & Technology Resources an online resource for computational, engineering & technology publications
	not logged in - login
Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	International Journal of Railway Technology ISSN 2049-5358 IJRT, Volume 7, Issue 3, 2018 Using Active Ultrasonics to Measure Wheel-Rail Contact During a Running-in Period S. Fukagai¹, T. Ban¹, K. Makino¹, M. Kuzuta¹ H. Chen¹, H. Brunskill² and R.S. Dwyer-Joyce² ¹Railway Technical Research Institute, Tokyo, Japan ²Leonardo Centre for Tribology, University of Sheffield, Sheffield United Kingdom doi:10.4203/ijrt.7.3.1 download the full-text of this paper Full Bibliographic Reference for this paper S. Fukagai, T. Ban, K. Makino, M. Kuzuta H. Chen, H. Brunskill, R.S. Dwyer-Joyce, "Using Active Ultrasonics to Measure Wheel-Rail Contact During a Running-in Period", International Journal of Railway Technology, 7(3), 1-20, 2018. doi:10.4203/ijrt.7.3.1 Keywords: flange climb derailment, running-in, contact stiffness, real contact area, ultrasonic measurements. Abstract Flange climb derailment is most likely to occur during the wheel-rail running-in phase, such as just after the railway vehicle wheels have been re-profiled or during morning rush hour. It is thought that the underlying cause is an increase in traction due to changes in the contact between wheel and rail. However, the mechanism of this increase in traction remains a subject of continuing controversy. Active ultrasonic measurements have been effectively used to measure wheel-rail contact conditions, particularly the contact stiffness. In this study, the ultrasonic method is used to characterise the wheel-rail contact during running-in whilst the surface roughness of the wheel reduces due to cyclic loading against the rail. An array of sensors was mounted behind the wheel flange so as to reflect ultrasound directly from the contact. An initial investigation was carried out to understand the measurement resolution of this ultrasonic array transducer. A static measurement was then performed by traversing the ultrasonic array transducer across the wheel when statically loaded against the rail. Following this, the same array transducer was fixed to the wheel and dynamic measurements were carried out. These measurements were cyclic to investigate the effect on changing surface topography. From this, the relationship between the slip and the contact stiffness was investigated. It was found that an increase of contact stiffness was measurement after slip motion was recognized. Both the static and dynamic measurements showed a difference in the wheel-rail contact conditions. In the case of the rolling condition, the peak position of the contact stiffness in the contact area shifted from the centre of the contact to the exit side. From the cyclic rolling tests, it was observed that the change in surface topography resulted in an increase in interfacial contact stiffness. This phenomenon indicates that there is an increase in real area of contact between the wheel flange and the rail gauge corner during running-in. download the full-text of this paper (PDF, 20 pages, 6612 Kb) go to the previous paper go to the next paper return to the table of contents return to IJRT purchase this issue (price £80 +P&P)
Back to top	©Civil-Comp Limited 2023 - terms & conditions