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

在滚轧试验台上进行了铁路轮对滚轧的缩比模型试验，测量了三维方向的混沌振动时间序列数据。从时间序列数据构造准相空间轨道数据，详细计算了最大李雅普诺夫指数。结果发现，在混沌振动所需的自由度的数量是涵盖从3到4。混沌振动的一个显著特征是“双峰”现象随轧制速度的增加而增加。通过与实验数据的比较，对常用的解析模型进行了评价。结果表明，若不对各参数进行不切实际的调整，模拟结果与实验结果不可能接近。为了模拟轮对在滚柱试验台上的混沌行为，在模型中加入了两个关于轮缘与轨侧碰撞情况的假设。一个是向前作用在凸缘上的摩擦力，另一个是向后作用在胎面上的摩擦力。仿真结果的波形和PSD与实验数据吻合较好，通过改进后的分析模型，可以估计车轮在混沌滚动过程中的侧向力。因此，将混沌振动分析模型推广到实际结构中，可以用来评估货车或车辆在混沌振动下的行驶安全性。

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.