Research on Vibration Transmission Characteristics of Subway Vehicles Based on Vibration Transmissibility

［Objective］ To ensure that the vibration level of subway vehicles meets design standards during operation, it is necessary to evaluate the vibration isolation performance of subway vehicles using the vibration transmissibility as a key indicator, and introduce a coherence function to assess the quality of the vibration transfer function. ［Method］ Acceleration sensors are installed at critical locations on the subway vehicle to collect acceleration signals from various components. Based on these data, the vibration transfer functions and coherence functions for different transmission paths are calculated to quantify the vibration transmission from the excitation point to the target point and the correlation between the two. Additionally, the vibration transmission paths of the primary suspension, secondary suspension, and from the car body underframe to the interior floor are analyzed. ［Result & Conclusion］ The average vibration isolation rate from the axle box to the frame end is approximately 60%, while it reached 80% from the middle frame to the car body underframe, indicating that both the primary and secondary suspension systems exhibit excellent vibration reduction effects. For specific frequency ranges (e.g. 10~20 Hz, 40~60 Hz), the vibration characteristics of the frame end and car body underframe show significant correlations with the axle box and the middle frame, respectively. However, the vibration transmission relationship from the car body underframe to the interior floor is not significant, as the vibration at the floor location is influenced by multiple factors.