A model for rolling contact failure

Rolling contact stress and failure analyses were conducted for the Hadfield steel (manganese steel) and the Bainitic alloy (J7). The first alloy is used in diamond crossings and frogs in the railroad industry while the second alloy is a candidate for such applications. A series of fatigue experiments were conducted on these alloys to establish the damage parameters. The proposed fatigue damage parameter incorporated the role of both shear and normal stress ranges on the 'critical' plane upon surveying all planes at a material point. Maximum local plastic strains, accumulated strains, and three-dimensional residual stresses were computed under pure rolling conditions for p_o/k (Hertzian pressure normalized by yield stress in shear) values in the range 4.0 to 8.0 using a semi-analytical approach. A multiaxial stress-strain plasticity model developed by the authors was used in the calculations of the contact stress and strain fields. The advantage of this model over the previous models is that it predicts the correct trends in the material ratchetting rate and non-proportional loading response. For life prediction, a new combined ratchetting-multiaxial fatigue damage model was presented. The damage at different depths below the surface was interrogated with this model to determine the location where failure will originate. The results show that the Bainitic alloy exhibits longer lives under the same Hertzian pressure and for both materials the life is finite when the normalized pressure, p_o/k ratio, exceeded 4.0.