Modelling and simulation of nonlinear dynamic characteristics of yaw dampers subjected to variable temperature operation condition of high-speed trains

The dynamic performance degradation of high-speed trains (HSTs) under complicated operating environment, such as low-temperature condition, has attracted increasing attention. This paper presents a study on the nonlinear dynamic characteristic variations of yaw dampers under variable temperature conditions and their effects on the nonlinear hunting stability of HSTs. An accurate physical parameter model that considers temperature variation is formulated for the yaw dampers. This model is capable of predicting the nonlinear dynamic characteristics of hydraulic yaw dampers subjected to variable temperature operation of HSTs. The hunting stability of HSTs considering the variations in the yaw damper dynamic characteristics caused by complicated low-temperature conditions is investigated by the HST vehicle system dynamics simulations. The results demonstrate that the reduction of environment temperature significantly increases the dynamic stiffness and damping of the HST yaw dampers. The dynamic performance degradation in the yaw damper influences the nonlinear hunting stability of the HSTs. The grazing bifurcation of HST vehicles exists under low temperature and low equivalent conicity, which triggers the serious low-frequency hunting motion and deteriorate the operational stability of HSTs. Moreover, the operation speed range of the grazing bifurcation becomes narrower as the temperature increases.