Rolling Contact Fatigue in Ansys Multiphysics

 If you want to make stress field of a rolling contact, the first step is to use ready closed form results. In fact, it is not obvious at all even with exact results, what you can apply to predict fatigue. See these papers

On the Dang Van fatigue limit in rolling
contact fatigue

International Journal of Fatigue, Volume
28, Issue 8, August 2006, Pages 852-863

M. Ciavarella, F. Monno, G.
Demelio

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

Mike gave you a good start point. If you are really looking at the analysis using ANSYS, these three papers might help. They include both S-N curve-based and fracture mechanics-based approaches. The focus is on the shattered rim failure (subsurface cracking) rather than surface cracking.

Liu, Y., Liu, L., Stratman, B.,  Mahadevan, S.. Multiaxial fatigue reliability analysis of railroad wheels. Reliability Engineering and System Safety, Vol. 93, Issue 3, pp. 456-467, 2008.

Liu, Y., Liu, L., Mahadevan, S. Subsurface fatigue crack propagation under rolling contact loading. Engineering Fracture Mechanics, Vol. 74, pp. 2659-2674, 2007.

Liu, Y., Stratman, B., Mahadevan,  S. Fatigue crack initiation life prediction of railroad wheels. International Journal of Fatigue, Vol. 28, Issue 7, pp. 747-756, 2006. 

Hope it helps.

Yongming