FAILURE IDENTIFICATION METHOD OF FASTENING SYSTEM BASED ON RAIL RESPONSE UNDER PULSE EXCITATION

Focusing on the failure detection of high-speed railway ballastless track fastening system, it proposed a failure identification algorithm based on the rail vibration response under pulse excitation. The failure of the fastening system was simulated by removing the elastic bar manually. The time-domain vibration responses of the rail with both functional and failed fasteners under pulse excitation were measured with the 1∶1 full-scale model in the laboratory. By carrying out the Fast Fourier transform and the octave analysis, the vibration acceleration levels of the rail under functioning and failed fastener conditions were obtained. By adopting the rail acceleration level difference and the characteristic frequency band percentage with and without failed fasteners as the evaluation indicator, the influence of frequency band division, vibration acceleration difference threshold and characteristic frequency band percentage threshold on the identification accuracy were further studied. The fastening system failure identification algorithm was proposed and the sensitive parameters for the failure of fasteners were selected. Together with the laboratory test results and field tests in Beijing-Shenyang high-speed railway, the effectiveness of the algorithm was verified. On this basis, the influence of the fixing position of the measuring accelerometer, the existence of non-target failure fasteners in the near-by span, and the human operation error on the recognition accuracy were further studied. The results show that the accuracy of the fastener failure identification algorithm proposed in this paper can reach 100% under the condition of one-sided failure of the fastener. When fasteners' failures on near-by span exist, the detection accuracy rate of the target fastener failure is also 100%. When the measuring accelerometers are located on the rail web and rail bottom where the target fastener is, the detection accuracy rate is above 95%. By taking the center line of the fastener as the reference, the detection accuracy rate is above 95% when the deviation between the excitation position and the reference position is less than 6 cm, or the deviation between the accelerometer fixing position and the reference position is less than 6 cm along the line operation direction.