To study the wheel/rail rolling contact fatigue of high-speed trains, we obtain the distribution of contact forces between wheel and rail by introducing the strain-rate effect. Based on the finite element simulation, a two-dimensional finite element model is established, and the process of a wheel rolling over a crack is analyzed to predict the crack propagation direction. The statistics of possible crack propagation angles are calculated by the maximum circumferential stress criterion. The crack path is then obtained by using the average crack propagation angle as the crack propagation direction according to Weibull distribution. Results show that the rail crack mode of low-speed trains is different from that of high-speed trains. The rail crack propagation experiences a migration from opening mode to sliding mode under the low-speed trains; however, the rail crack mainly propagates in the opening mode under high-speed trains. Furthermore, the crack propagation rate for high-speed trains is faster than that for low-speed trains. The simulated crack paths are consistent with the experimental ones, which proves that it is reasonable to use the average value of possible crack propagation directions as the actual crack propagation direction.

The propagation behavior of the macrocrack and microcracks from short to long is investigated based on the Muskhelishvili’s complex potential method and the equivalent crack method. The effect of microcracks on the macrocrack propagation is analyzed. The improved stress intensity factor at the crack tip and the theoretical solution of plastic zone are obtained. The equivalent crack method is applied to compute trajectories of the kinked microcracks. The direction of crack propagation is calculated based on the maximum circumferential tensile stress criterion. Three configurations of microcracks in front of the macrocrack tip are considered: arbitrarily oriented and located microcracks, parallel microcracks, and fan-shaped microcracks. Parallel distributed microcracks allow the macrocrack to propagate at the fatigue threshold ΔK_th rapidly, then fan-shaped microcracks, followed by arbitrarily oriented and located microcracks. The results show that the physically short crack can propagate well below the ΔK_th while the crack surface is closure-free. Moreover, the closure effect may delay the propagation process of long crack, taking longer for it to coalesce with the microcrack. The results are consistent with the experimental observations and can provide some useful information to predict the fracture or damage behaviors at the macrocrack tip for the material containing microcracks.