Fatigue Analysis of Rail Subject to Traffic and Temperature Loading

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Association of American Railroads
The maintenance of the track structure, and in particular, the prevention of rail failure is an area of continuing concern to the railroad industry. In view of the serious nature of rail failure, defined here to be the occurrence of rail defects, there exist, a need for the reliable prediction of rail service life in track. With the availability of this service life prediction capability, the track engineer would be in a position to anticipate rail defect occurrence and corresponding rail failure and consequently develop an inspection and maintenance cycle and schedule that would result in a safer and more efficient track structure. Recently, a fatigue analysis methodology for the prediction of rail service life was presented (1). This methodology utilizes a three dimensional characterization of the service load environment in conjunction with rail material fatigue properties to calculate an anticipated fatigue life of rail in mainline service. Reference (1) however, was restricted to rail bending stresses and utilized a hypothetical load environment. In this paper, the analysis is extended to include contact, and thermal stresses as well as bending stresses. The effect of rail head wear is also considered. The load spectrum that is utilized was developed from measurements taken on U.S. mainline track and the material properties are obtained from published laboratory test data. The fatigue life calculated by the presented method is compared with a survey of U.S. service rail fatigue failure (2). It is noted that mainline service life, in accumulated tonnage, is significantly greater for heavier rail sections than for lighter rail sections subject to similar traffic loading. This appears to support the contention that contact stress theory alone is not sufficient for the prediction of rail service life. Rather, a combination of longitudinal rail incenses due to contact loading at the wheel-rail interface, bending of rail on the track foundation, and thermal effects of temperature must be used for the proper prediction of rail defect, particularly transverse defect occurrence.
Rail failure, Fatigue analysis, Thermal effects
Zarembski, A. M., & Abbott, R. A., “Fatigue Analysis of Rail Subject to Traffic and Temperature Loading”, Heavy Hauls Railways Conference, Perth, Western Australia, September 1978.