Post Hatfield rolling contact fatigue: the effect of residual stress on contact stress driven crack growth in rail, part 1: the model

This report presents a model for investigating the effect of residual stress in railway rails on the rate of crack growth for shallow angle rolling contact fatigue cracks. Crack growth rate results are presented for a single contact condition only, and for a single set of residual stress input conditions. Further contact conditions and residual stress distributions will be investigated and presented in a later report. Support for the crack growth rate results is presented using contour plots of stress beneath the rail-wheel contact. The results indicate that for a shallow (30 degrees below the surface) rolling contact fatigue crack under the conditions investigated, the crack growth rate is particularly sensitive to vertical residual stress in the rail. At crack lengths up to around 25mm predicted crack growth rates are around 1.5 those in the absence of residual stress, while at longer lengths the growth rate may be up to 100 times the rate predicted without residual stress. However, at such long crack lengths rail bending may be important, and this is not included in the current model. This report contains revised information on the residual stress input data, and supersedes earlier versions of the report