Abstract: In order to study the effect of vertical bending modal node position on the ride comfort, the car body is considered as a variable cross-section Euler beam with multi-sections on the basis of its structural properties and mass distribution. The vertical dynamic model of the vehicle including the first-order vertical bending mode of the car body is established, and measures to improve the elastic vibration of car body are put forward. The relationship between parameters of variable cross-section beam and mode of vehicle body is studied. The analytical results indicate that traditional model with uniform cross-section beam cannot accurately describe the vertical bending mode. There are deviations between traditional model and vehicle body mode in the re ady state, especially in terms of amplitude and nodes position. Longitudinal distribution of bending stiffness and mass affects the mode shape of vertical bending. Increasing the bending stiffness and reducing the mass distribution in the middle of the car body can increase the space between nodes of bending mode, and increase the frequency of bending vibration. The response of vehicle under random excitation of track is obtained by frequency domain analysis method. When the bending nodes are near the bolsters of the vehicle, the elastic vibration of the car body decreases obviously. Also, ride comfort index in the middle of car body is reduced by 50% at the speed of 300 km/h.

Key words: high-speed train, flexible car body, variable cross-section beam, vertical bending, modal node