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 us ed in diamond crossings and frogs in the railroad industry while the second alloy is a candidate for such applications. A series of fatigue experiment s were conducted on these allays to establish the damage parameters. The pr oposed fatigue damage parameter incorporated the role of both shear and nor mal stress ranges on the 'critical' plane upon surveying all planes at a ma terial 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 i n the range 4.0 to 8.0 using a semi-analytical approach. A multiaxial stres s-strain plasticity model developed by the authors was used in the calculat ions of the contact stress and strain fields. The advantage of this model o ver the previous models is that it predicts the correct trends in the mater ial ratchetting rate and non-proportional loading response. For life predic tion, a new combined ratchetting-multiaxial fatigue damage model was presen ted. The damage at different depths below the surface was interrogated with this model to determine the location where failure will originate. The res ults show that the Bainitic alloy exhibits longer lives under the same Hert zian pressure and for both materials the life is finite when the normalized pressure, p(o)/k ratio, exceeded 4.0. (C) 1999 Published by Elsevier Scien ce S.A. All rights reserved.