ABSTRACT
I. Introduction ...................................................................................................................... 121
II. Contact Conditions at the Wheel-Rail Contact.............................................................. 122
III. Wear and Other Surface Damage Mechanisms............................................................... 125
A. Wear ......................................................................................................................... 125
B. Plastic Deformation.................................................................................................. 127
C. Rolling Contact Fatigue ........................................................................................... 129
IV. Friction ............................................................................................................................. 131
A. Wheel-Rail Friction Conditions ............................................................................. 132
B. Friction Modification ............................................................................................... 133
C. Adhesion Loss .......................................................................................................... 134
D. Increasing Adhesion................................................................................................. 135
V. Lubrication and Surface Coatings ................................................................................... 136
A. Benefits of Lubrication ............................................................................................ 136
B. Methods of Lubrication Application ....................................................................... 136
C. Problems with Lubrication....................................................................................... 137
D. Lubricator System Selection and Positioning ......................................................... 137
E. Surface Coatings ...................................................................................................... 138
Acknowledgments ........................................................................................................................ 138
References..................................................................................................................................... 138
Tribology, the science and technology of friction, wear, and lubrication, is an interdisciplinary
subject. It can therefore be addressed from several different viewpoints. This chapter focuses on the
friction, wear, and lubrication of the tiny contact zone (roughly 1 cm
), where steel wheel meets
steel rail, from a mechanical engineer’s viewpoint. In contrast to other well-investigated machinery,
such as roller bearings, the wheel-rail contact is an open system. It is exposed to dirt and particles
and natural lubrication, such as high humidity, rain, and leaves, all of which can seriously affect the
contact conditions and the forces transmitted through the contact. In contrast, in roller bearing the
ball-cage contacts are sealed away. The steel rail meets a population of steel wheels from a number
of different vehicles and the form of both the wheels and the rail can change due to wear. In contrast,
a roller bearing meets the same rollers without any form change of the contacting bodies.
