ELASTIC-PLASTIC ANALYSIS FOR ROLLING CONTACT STRESSES AND DEFORMATIONS OF RAIL UNDER MULTIPLE-STEP NON-STEADY STATE LOADING

Rolling contact stresses and deformations of rail under the multiple-step non-steady state loading are analyzed by the elastic-plastic finite element method. Multiple-step loading implies the action of continuous locomotive/car wheels or multiple passages of trains over a rail. Repeated wheel rolling and sliding are simulated by multiple translations of varying normal and tangential surface tractions across rail running surface. An advanced cyclic plasticity model proposed by Jiang and Sehitoglu that considers the material ratcheting effect is employed. A wavy rail running surface profile due to the uneven plastic deformation is formed under the application of the multiple-step non-steady state loading. Multiple-step loading has an insignificant influence on the residual stresses of rail. The residual shear strain, surface displacements, wave depth and accumulated residual equivalent plastic strain increase with increasing number of locomotive wheels rolling passages. After the passages of the locomotive wheels the increasing passage of car wheels reduces the residual shear strain, surface displacements and wave depth, and aggrandizes the residual equivalent plastic strain. However, the increasing rate of the residual equivalent plastic strain becomes smaller when the car wheels pass through the rail. With an increasing number of train passes, the ratcheting rate of the residual shear strain, surface displacements and wave depth shows a decaying tendency.