Research On The Mechanism Of Coupler And Draft Gears In The Collision Process Of Intercity Trains

In this paper,the mechanism of coupler and draft gears in the collision process of intercity trains is studied deeply by building an exact mechanical model and performing collision simulation calculations.The specific effects of coupler and draft gears on the crashworthiness and collision behaviors of intercity trains are analyzed in detail.Firstly,according to the working principle and kinematic relations of the coupler and draft gear,a mechanical model of the coupler and draft gear with a nonlinear hysteresis characteristic and nodding and yaw motions is built.Secondly,a one-dimensional longitudinal simulation model of an intercity train collision is built.By changing the resistance forces and the compression strokes of the head coupler and intermediate couplers,the effect of the energy absorption scheme on the crashworthiness of the trains is studied.The optimal value of the head coupler's compression stroke is obtained when the collision speed is constant.When the head coupler stroke is less than the optimal value,the energy absorption of the cab is positively related to the head coupler's stroke.When it is above the optimal value,the energy absorption of the cab is negatively related to the head coupler's stroke.The maximum average acceleration of the cab vehicle is negatively correlated with the resistance forces of the intermediate couplers and is independent of the compression strokes of the intermediate couplers.The maximum average acceleration of an intermediate vehicle is negatively correlated with the compression stroke of the head coupler,the resistance forces and compression strokes of the intermediate couplers.Then,a detailed three-dimensional simulation model of an intercity train collision is built to study the influence of coupler and draft gears on trains' collision behaviors.When a frontal collision happens between two identical intercity trains on a linear track,the intermediate couplers will perform nodding and yaw motions at the same time,and the motions are symmetrical about the collision interface of the two trains.From the train head to the end,the vertical and lateral rotation angles reduce gradually.The first two vehicles of the active and passive trains have the risk of derailment,and the rotation response of the intermediate couplers is one of important factors of the derailment.When the lateral rotation angles of the intermediate couplers are constant,with the increasing of the elevation angles of the intermediate couplers,the derailment risk of the second-end bogie of the former vehicle connected with the coupler increases,but the derailment risk of the first-end bogie of the latter vehicle connected with the coupler decreases.The effect of depression angles of the intermediate couplers on the derailment response is opposite to the elevation angle's.The coupler longitudinal force in the collision process is mainly carried by the underframe of the carbody.For the aluminum alloy carbody selected in this paper,the underframe can carry about 90%of the coupler longitudinal force.Finally,the effects of the initial vertical rotation angle and the collision speed on the train collision behaviors are studied.When the initial vertical rotation angle of an intermediate couplers is zero or is an elevation angle,the nodding motion of the coupler will always be an elevation posture.When the initial vertical rotation angle is a depression angle,the nodding motion of the coupler will always be a depression posture.The initial vertical rotation angles of intermediate couplers do not affect the lateral rotation angle of the coupler.Besides,the increasing of the collision speed increases the total amount of energy absorption and the size of the vertical and lateral rotation angles of intermediate couplers.When the nodding motions of intermediate couplers are constrained,the yaw motions of the couplers will be intensified,which will intensify the the intercity trains' derailment risk and lateral buckling behavior.