One solution to surface fatigue of rails, currently being investigated by the EU project Infrastar, is to coat the surfaces with a material which reduces or eliminates ratchetting. To enable reliable fatigue design of a two-material rail system, a systematic approach incorporating shake down analyses and lab and field trials has been adopted. Three-dimensional finite element calculations of wheel-rail rolling-sliding contacts have been performed to evaluate the shakedown limits. The two-material system performance is studied in detail with respect to rolling contact fatigue performance. Parameters incorporated in the calculations are: the combination of coating and substrate materials, coating thickness, and wheel-rail friction. Design curves are produced for a realistic wheel-rail contact example which illustrate how the improvement in shakedown performance of coated rails varies with the depth of coating, friction, and the strength of the coating-substrate materials. The results are discussed in the light of lab tests.
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