Boundary Problem Solutions Would Place Future of Rail Transport on Fast Track

Yasufumi SUZUKI
General Manager, Railway Dynamics Division

    Raising the levels of safety, environmental friendliness, ride comfort and other railway service indices is essential for the future development of rail transport within society. In order to accomplish the necessary improvements, we have to carefully investigate the basic phenomena specific to railway systems and steadily address the issues related to them. Most of these concern the so-called boundary problem, which is thought to exist at the contact point between two bodies such as contact wire/pantograph and wheel/rail. Boundary problems also include rolling noise and other issues induced by the interactive forces between different objects and structures.
    Boundary problem features are as follows.
Old and new: One of the age-old railway problem areas is wheel/rail contact, which is connected with wide-ranging issues such as safe train acceleration and braking and how to reduce maintenance costs caused by track and vehicles wear and tear. The subject has been studied for a long time. Nevertheless, a number of problems remain unsolved even now. The friction coefficient is understood to play an important role in wheel climb derailments, for example. However, the wheel and rail surface conditions that raise the coefficient value sufficient to cause derailments remain unknown.
Complicated Complicated: In general, it is very difficult to understand what happens and how bodies interact at the contact point, because a number of complex factors are related to and involved in these issues. For example, the relationship between the wheel/rail roughness and the contact force, vibration induced by the contact force and vibration-induced noise emissions are all understood to have some bearing on rolling noise levels, but are as yet not fully understood.
Difficult to measure measure: It is often very difficult to measure the interacting force between two moving objects. There is no alternative but to gauge what happens at the contact point other than by observing measurable parameters.
Interdisciplinary: Expertise from several academic fields are needed to study just one boundary problem, as it requires a number of approaches and the integration of each to solve it. For example, the contact wire and contact strip wear needs a number of specialties such as dynamics to look into the contact force, material technology for the wear characteristics, and electrical engineering or electronics to determine friction and wear rates when in operation.

    The level of boundary problems to be solved will become higher depending on future rail transport requirements. The progress of technologies related to measurement or the development of a new analysis method will provide new approaches to the problems, which will make it possible to break into virgin territory. Boundary problems, which require a comprehensive approach from various academic fields, are one of the most important research fields to which RTRI should be constantly applying its expertise. Great efforts will inevitably be required if we are to solve future rail transport problems.