Measuring, evaluating and assessing the transmission of vibration through the seats of railway vehicles

Abstract

The transmission of vibration through a passenger train seat to the seat pan and to the backrest has been measured in the fore-and-aft, lateral and vertical directions with 12 subjects using 0.5–40 Hz random vibration (with both single-axis and tri-axial excitation) and using simulated tri-axial train vibration. There were small differences in transmissibilities obtained using single-axis and tri-axial random vibration but greater differences in transmissibilities between tri-axial random vibration and simulated train vibration. Seat effective amplitude transmissibilities (SEAT values) were similar for single-axis and tri-axial random vibration but differed between tri-axial random vibration and simulated train vibration. The SEAT values measured using both tri-axial random vibration and simulated train vibration were well predicted from the seat transmissibilities measured using single-axis random vibration. It is concluded that either single-axis or tri-axial vibration excitation can be used when quantifying the transmissibility of a seat and identifying seat resonances. A SEAT value depends on the vibration spectrum in the vehicle and so the SEAT value for a train seat cannot be obtained using vibration unlike that in a train. A useful SEAT value for a train seat can either be measured (by simulating tri-axial train vibration in a laboratory) or calculated (from measurements of vibration in a train and measurements of seat transmissibility obtained using random vibration in a laboratory). The findings of this study may assist the optimisation of seat testing standards including the laboratory method for evaluating the transmission of vibration through the seats of railway vehicles defined in a current international standard.