Finite Element Simulation of the Flat-Induced Wheel-Rail Impact Based on the Cowper-Symonds Empirical Model

The wheel-rail interaction is a major concern in research for high-speed rail transport.As a main type of wheel/rail failure, the wheel flats exert serious restriction on the stability and safety of high-speed trains.In this study, a three-dimensional wheel-rail rolling contact model with a flat was built using the Hypermesh software, and the corresponding finite element simulation was conducted, based on the Cowper-Symonds empirical model, using the LS-DYNA 3D explicit algorithm.Influences of the train speed, flat length and axle load on the wheel-rail impact response were discussed, respectively.The simulation results indicate that the maximum vertical wheel-rail impact force is significantly larger than the corresponding static axle load due to the presence of a wheel flat, and the maximum von-Mises equivalent stress and maximum equivalent plastic strain are observed on the wheel-rail contact surface.The strain rate-dependent constitutive parameters of the wheel/rail steels have no influence on the maximum vertical wheel-rail impact force; however, due to the hardening effect of the strain rate, the maximum von-Mises equivalent stress obtained from the Cowper-Symonds model is obviously larger than that derived from the rate-independent one, while the maximum equivalent plastic strain derived from the Cowper-Symonds model is smaller than that under rate-independent one.Besides, the wheel-rail impact response is demonstrated to be sensitive to the train speed, flat length and axle load.These findings can provide technological supports for safety design and assessment of the wheel-rail system.