Dynamic performance prediction of railway pneumatic suspensions

This paper studies the dynamic performance of a typical pneumatic secondary suspension system of railway vehicles up to 300 Hz. A detailed non-linear finite element model is introduced, which incorporates a description of the bellows, surge reservoir, pipeline and emergency spring. The model is validated experimentally at low frequencies and extended to predict the suspension’s behaviour at higher frequencies. The study demonstrates that current phenomenological/mechanical and thermodynamic models cannot predict the dynamic behaviour of the pneumatic suspension at frequencies higher than 30 Hz, whilst in the 30 to 300 Hz frequency range significant dynamic effects and resonances occur due to standing waves inside the pipeline and to structural vibration modes of the bellows coupled to the emergency spring. The results presented in the paper demonstrate that the pneumatic suspension can significantly affect the transmission of structure-borne vibration from the running gear to the car body, and hence its design must be carefully considered to minimise these effects.