Railroad rails can fail by a number of mechanisms including wear and surface initiated rolling contact fatigue (RCF). Higher strength and deformation-resistant rail steels have been successful in helping to alleviate wear, but have led to concerns about the relationship between material properties and RCF resistance.;Validation studies showed that the model predictions agreed very well with experimental results when the steels used had properties similar to those used in formulating the model.;A laboratory analysis of head-hardened rails, removed from a heavy haul site at various stages of life, has enabled a study to be made of the incidence of RCF cracks and the role of the white etching layer (WEL) found on the rail head. The cracks occurring down the center of the rail were shown to be associated with the WEL formed very early in the life of the rail. The extent of the WEL and the population of cracks decreased with increasing traffic. Some cracks penetrated beyond the WEL-pearlite interface and grew to a depth that was not always removed during normal maintenance grinding. The crack growth rates found in these rails were about 8.5 times lower than those found in Amsler test specimens.;This work also looked at developing a test procedure to generate subsurface contained plastic deformations. An attempt was made to relate an existing wear rate prediction model and the RCF life model to arrive at a relationship to predict the pearlite interlamellar spacing/hardness to minimize the wear rate and maximize the RCF life.;A simple material model has been developed to predict the RCF life of eutectoid rail steels for water lubricated conditions using an Amsler twin-disc rolling/sliding testing machine. RCF life is found to be a function of the maximum Hertzian contact stress, Po, the hardness, H and HPo. This empirical relationship predicts that as Po increases and/or H decreases, RCF life decreases. The model can be modified by replacing the hardness by the pearlite interlamellar spacing of the steel. The effect of different lubricants can be included by considering the coefficient of friction.
展开▼
