Rail Research: Meeting the Challenge of Modern Traffic Loading
Transportation Research Board
In light of the current trend in railroading toward heavier cars and trains, the railroad track structure is being called on to perform under an increasingly sever loading environment. As a result, the very nature of rail failure has changed. This change in the modes of rail failure has resulted in changes in criteria for fail replacement and consequently in changes in inspection and maintenance practices. Track rail once lasted until it literally wore out. Under today's severe loads, however, fatigue-initiated cracks in the railhead can result in premature fracture of the rail. Furthermore, it is often not possible to see the fatigue crack, even at its critical point. Ultrasonic or magnetic inspection techniques must be used to detect these hidden defects so that they can be removed. Rail-end batter, the traditional replacement criterion for tangent track, has been significantly reduced by the increasing use of continuously welded rail. In its place, however, fatigue-induced defects, either in the rail or at a weld, have emerged as the dominant rail-replacement criterion for tangent track. On curves, severe gage face wear, plastic flow of the railhead, and even crushed rail are all major problems that combine with initiation of fatigue defects to shorten the service life of rail. To better understand the problem, one must only consider that a stationarly 91-Mg (100-ton) car with a static wheel load of 146 kN [33000 Ibf (33 kips)] transmits a contact stress of 1200 MPa (175000 lbf/in^2) to the head of the rail. The yield strength of the rail steel is only 520 MP (75000 lbf/in^2)/ The result can be seen in Figure 1: rail wear, fatigue defects, or both. Thus, in recent years, rail research has been directed toward the problem of defining, quantifying, and ultimately extending rail service life. It is the purpose of this paper to briefly define and quantify some of these modes of rail failure and to discuss the current and future directions of rail research in North America.
Traffic loading, Track structure, Rail failure
Zarembski, A. M., “Rail Research: Meeting the Challenge of Modern Traffic Loading”, Annual Meeting of the Transportation Research Board, January 1980. (Transportation Research Record 744).