Boundary element analysis has been performed for the cycle of stress intensity factors at a surface initiated rolling contact fatigue crack tip under a Hertzian contact pressure distribution. The model includes the effects of Coulomb friction between the crack faces and the possible influence of fluid penetrating into the crack. Three possible models of the influence of fluid to propagate the crack have been investigated, namely, (a) fluid lubrication model; (b) hydraulic pressure model; (c) fluid entrapment model. The analysis results indicate that when the fluid entrapment model was used, the values of generated mode I and II stress intensities were reasonable and the results were consistent with the behavior of the crack. Therefore, the fluid entrapment model is considered to be the most promising to explain the behavior of the rolling contact fatigue cracks.

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