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Compressive residual stresses are introduced into the rim of a railway wheel during manufacture to delay rolling contact fatigue initiation and to slow early crack growth. However, severe tread braking can reduce this stress state through elevated temperatures, thermal softening, and local plastic deformation. Subsequent cooling may redistribute the residual stresses or generate near-surface tensile stresses, thereby altering the mean stress state that governs fatigue initiation. To investigate this behavior, this study presents a sequential thermomechanical model of an ER7 railway wheel in which the temperature, stress, plastic strain, and hardening variables are continuously transferred between successive stages. The simulated history includes rim quenching, annealing, severe drag braking, cooling to ambient temperature, and subsequent wheel–rail contact. Frictional heat was applied at the wheel–brake-block interface, and a rolling contact was introduced at the wheel–rail interface. Temperature-dependent elastic and cyclic plastic properties were used, including the softening of ER7 steel at high temperature, so that the post-braking residual stress field develops from thermal expansion, plastic flow, and reverse yielding during cooling and is not prescribed as an initial condition. The mechanical contact model was first checked against Hertzian theory. For the selected loading condition, the analytical peak contact pressure was 1382 MPa and the finite element model gave 1454 MPa, a difference of 5.2%. A traversing pressure and traction distribution was then applied to obtain depth-resolved stress and strain tensor histories for the multiaxial fatigue assessment. Predicted temperatures and residual stresses were compared with the admissible rim stress criterion of EN 13979-1.
| Topic Area | Fatigue, Corrosion and Structural Integrity of Engineering Structures and Mechanical Systems |
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