Effect of Rail Section and Traffic on Rail Fatigue Life

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American Railway Engineering Association
The current trend towards increasing traffic and wheel loads has focused industry attention on maintenance of the track structure. In particular, the problem of rail failure and replacement has emerged as a key issue in the track maintenance, safety, and economics arenas. The ability to reliably predict rail service life for different traffic and track conditions is of paramount importance in examining and developing suitable maintenance procedures. Furthermore, the proper matching of rail section size with traffic and track conditions is essential for any cost effective maintenance program. Traditionally, the dominant criterion for the replacement of rail in mainline track has been either rail end batter or rail head wear. Increasing use of continuously welded rail has significantly decreased the occurrence of rail head batter. Thus rail head wear remained as the dominant rail replacement criterion. However, with the increasing traffic loads, particularly the increasing wheel loads, that the track structure is being called upon to support, the development of fatigue "defects" in the rail is emerging as a major replacement criterion for mainline tangent track. In fact, current and proposed safety criteria now emphasize the detection of fatigue defects as they develop in tangent track. Thus, it appears that in many instances, fatigue, rather than wear, is the replacement criterion for rail in service. Recent development of a fatigue analysis methodology for prediction of rail service life in mainline tangent track was reported in References (1) and (2). This methodology utilizes a characterization of the service load environment together with rail material fatigue properties to calculate the service life of the rail. Reference (2) presented the complete analysis methodology and compared the calculated results with data obtained from service experience. The correlation was quite good. The objective of this paper is to extend the results presented previously to study the effect of changing the rail section size on the rail service life. Additionally, the effect of different traffic loadings, specifically mixed freight vs. unit train traffic, and the effect of varying track support conditions will be investigated.
Rail failure, Rail section size
Zarembski, A. M., “Effect of Rail Section and Traffic on Rail Fatigue Life”, American Railway Engineering Association, 78th Annual Technical Conference, Chicago, IL, March 1979.