Fatigue Test of Rail

Abstract

The purpose of the paper is to propose a test set-up for bending fatigue of rail on the basis of theoretical analysis. The proposed set up may be used with the knowledge of the representative effective wheel load on a system only. It may be used to determine the allowable bending fatigue stress/load of rail experimentally without resort to use of the fatigue test on the standard fatigue test specimen, and validate the currently available allowable bending fatigue stress/load. Thus, the paper reviews and discusses bending fatigue test parameters of a rail section such as test span, stress ratio, test load, loading cycle, loading frequency, and deflection. In literature, there exists a variation in the test span length which calls for a theoretical investigation to determine a basis of the test span. It is shown that a test span equal to the characteristic length of the track is a sensible technical choice for which the test load becomes equivalent to the representative effective wheel load on the system, and as such bending fatigue test is possible even without the knowledge of the allowable bending fatigue stress. Thus, the characteristic length of the track and the representative effective wheel load on a track system open a venue to determine the allowable bending fatigue stress of a rail section experimentally. In a paper by the author, the maximum possible stress ratio in a continuously welded rail track has been determined to be (-) 0.438. On the basis of this stress ratio, and suggested test span, a fatigue test set-up is proposed. Under the proposed test set up, the span is close to that of American Railway Engineering and Maintenance-of-Way Association (AREMA) test set up which might render the proposal unnecessary. Thus, the reasons for the proposal are explained in details. The test loads for different rail sections are estimated by using the allowable bending fatigue stress formula by the author. The test loads are compared with the effective wheel load and test loads proposed by AREMA and discussed. Review of AREMA test load is suggested.