Wheelset/Rail Interaction under Chaotic Vibration due to High-Speed Rolling

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The experiment for railway wheelset rolling was carried out on a roller rig using a scale model and time series data of the chaotic vibration were measured in three dimensional directions. Constructing orbital data in a quasi-phase-space from the time series ones, the maximum Lyapunov exponents were calculated in detail. It was found that the number of the degree-of-freedom required in the chaotic vibration is covered from 3 to 4. Here, the roll motion is also included in the number besides the lateral and yaw motions.A remarkable feature of the chaotic vibration is "doubling peaks" phenomenon increasing with the rolling speed. Conventionally used analytical model was evaluated comparing its simulation results with the experiment data. As a result, it was clarified that the simulated results can not close to the experiment data without unpractical tuning of the several parameter values.In order to simulate the chaotic behavior of the wheelset experimented on the roller rig, two assumptions were added to the model on the situation of the collision between the wheel flange and rail side. One is the friction force acting forward on the flange and the other is some one acting backward on the tread. Then simulation results in wave-form and PSD showed reasonable agreement with the experiment data.From the simulation using the improved analytical model it became possible to estimate wheel lateral forces during chaotic rolling. So that it is expected in the future to evaluate the running safety of a truck or a vehicle under chaotic vibration by extending the analytical model to the practical structure.