Abstract: Confirming of resonance mechanism of flexible car body is important for car body bending frequencies design and ride quality improvement of railway vehicle. To research the fundamental reasons of resonance of flexible car body, a vertical rigid-flexible coupling dynamic model of railway vehicle which includes the flexibility of car body is established, Green functions are applied to solve the partial differential equations of the dynamic system, the power spectrum densities of acceleration of car body and ride quality are calculated, the relationship between geometry filtering phenomenon and resonance of flexible car body is studied. Results show that comparing with the conventional mode superposition method, Green functions method can realize ‘one-time calculation’ of the whole modes of car body, and can present the vibrations of flexible car body in whole frequency bands, which is significant for studying and predicting the vibration performance of car body at high frequencies. Since frequency weighting of ride quality index in high frequency is low, it is reasonable to evaluate vertical ride quality by utilizing modal truncation method. Results also show that resonance of flexible car body is closely related to the vehicle running speed and geometry filtering phenomenon, the design of car body vertical bending frequencies only based on the frame bounce frequency is incomplete, it is supposed to take the influences of geometry filtering phenomenon into consideration.

Key words: Flexible car body, Geometry filtering, Green functions, Railway vehicle, Ride quality, Grinding force, Grinding mechanism., Tooth surface, 20CrMnTi steel