Post Hatfield rolling contact fatigue: the effect of residual stress on contact stress driven crack growth in rail: literature review

Crack initiation by rolling contact fatigue and subsequent crack propagation can be illustrated by Figure 1. The crack grows through three stages identified as stages I, II and III. During the early part of the crack life, growth is dominated by local contact stresses resulting from wheel rail forces, and later its growth is dominated by the bulk bending stresses produced by the rail supporting the vehicle. As the crack grows the rate of growth (the crack tip extension per cycle) varies depending on whether it is driven by contact patch stresses, bulk rail bending stresses or a combination of the two. Additional influences on the growth of the cracks include residual stresses in the rail (both those which remain after manufacture and those developed due to plastic flow of the rail steel during use) and continuously welded rail stress. Besides driving crack growth, contact loading also drives wear of the rail. Wear is significant because of its interaction with fatigue crack initiation and propagation. In some cases wear dominates and cracks simply wear away as fast as they are initiated. In other circumstances, the wear rate can be low allowing the cracks more time to propagate to a dangerous size