Probability of subsurface fatigue initiation in rolling contact

Artikel i vetenskaplig tidskrift, 2011

Subsurface initiated rolling contact fatigue cracks initiate in the vicinity of material defects. As these exist randomly in the material, fatigue will appear randomly under otherwise constant conditions. By combining statistical methods with a contact mechanics and fatigue analysis, probabilities of fatigue initiation are evaluated. The developed model takes as input contact geometry, contact load and the statistical properties of the material defects. It is shown that under some well-defined presumptions the probability of rolling contact fatigue initiation in a rolling wheel can be expressed by a simple formula. Based on this, the parametric influence is assessed and it is found that the mean material defect size has a large influence. The benefit of material cleanliness testing procedures and the influence of the allowed defect size on the risk of subsurface initiated rolling contact fatigue in railway wheels are then quantified with the aid of numerical simulations.