Abstract: There is crack found on the safety hanger mounted on the axle-box of railway metro. The finite element(FE) Analysis and field measurement were performed to study the crack mechanism, then the vibration level of the hanger is thoroughly evaluated. The excitation and natural response of the structure are analyzed, and solutions are provided and validated by the field measurement. The FE analysis shows that the lateral bending mode has the lowest frequency around 260 Hz, and a weak area on the inner corner of the hanger bottom can be noticed. This shows a good agreement with the field crack propagation on the hanger. Field measurement illustrates that the vibration level of the axle-box and safety hanger are strongly dependent on the track segments. It is noticed that it is the rail corrugation with a wavelength of 61.5 mm that causes the serious vibration of vehicle. A resonance can be noticed by considering the natural mode of safety hanger and the track excitation frequency, which is dependent on the vehicle speed and corrugation wavelength. A fatigue problem can be encountered resulting from this resonance. Consequently, solutions for this structure failure issue are provided, such as the rail grinding, design a new safety hanger or specify the service conditions of this kind structure. Additionally, validation tests are conducted for the rail grinding solution which depicts that the rail grinding can significantly reduce the vibration level of vehicle, and the safety hanger stress reduces more than 50%. However, there still exist corrugations on some track segments. The vehicle dynamic responses can be used to identify the corrugation level and location on track for further track maintenance.

Key words: field measurement, finite element analysis, rail corrugation, railway metro, structure fracture