An investigation of damage and reliability of metro bogies induced by Rail Corrugation

The safety of the metro system depends on the safe operation of all sub-components in both rolling stock and track systems. As the life of the system increases, the deterioration will grow; hence, some defects might be appeared, which can be considered from the point of view of safety. In recent years, a plethora of failures have been reported for the pick-up coil system which had been installed in the Tehran metro fleet. In this paper, through the Finite Element Method (FEM) and field test, causes for the failure of the pick-up coil were investigated. To achieve this goal, a field test was done on Tehran metro line ۱. Axle box and bogie frame accelerations were recorded and analysed. Moreover, modal frequencies were obtained via the FE approach for the pick-up coil. It has been observed that there are similar frequencies in excitation frequency and pick-up coil natural frequencies. In the next step, the dis-placements of the bogie frame on the top of the axle box in three directions, including the vertical, longitudinal, and lateral movements are applied to the pick-up coil supports as the excitation. A study on the cause of this defect demonstrated that rail corrugation plays a pivotal role. It is realized that the natural frequencies of the old design have coupling natural frequencies of the wheel (۸۰ and ۱۵۰ Hz) and corrugation exciting frequency range (about ۶۰-۸۰ Hz in the Tehran subway network); therefore, it causes a destructive resonance in the pick-up coil. In this regard, the Goodman-Smith criterion has been executed in order to analyse the fatigue life cycle. Finally, a modified design has been presented to eliminate the future possible failures