A preliminary study on generation of axle box vibration spectra for metro vehicles in China using the developed spectral synthesis method

In-service metro vehicles in China exhibit diverse vibration behaviours. This study focuses on analysing the vibration characteristics of these vehicles, with a particular focus on the complex non-stationary axle box vibrations measured on-site, as they closely correlate with wheel-rail interaction dynamics. A developed PSD-based synthesis method is first proposed to quantify the axle box vibration. The axle box vibration spectra of the metro vehicles in China are then generated from the measurements for various vehicles. Furthermore, a multi-line segment flat spectrum, designed specifically for the shaker loading, has been produced. The results show that the proposed method can determine the parameters (segment number, quantile) by the energy conservation law, which avoids the empirical value selection in previous methods and can be effectively utilized to generate the vibration spectra of the axle box. In addition, a notable distinction exists between the IEC 61,373 standard spectrum and the axle box vibration spectra of Chinese metro vehicles. While the former represents a single-peak spectrum ranging from 20 ~ 100 Hz, the latter consists of a multi-peak spectrum with peak frequency bands exceeding 100 Hz. The wear condition of the wheel-rail surface has a pronounced contribution to the vibration spectral magnitude. In cases of wheel-rail surface severe wear, the vibration spectrum values in the Z direction surpass the standard spectrum values across most frequencies, with the highest spectral value notably observed within 50 ~ 200 Hz. Such observations should be thoroughly taken into account in the analysis of fatigue damage to mounted equipment.