| Railway transportations in China are very busy and the intervals of train transportation are typically only a few minutes. Meanwhile, the lengths of operating lines can be as long as thousands of kilometers,yet the conditions of these lines are poor. Moreover, a large number of service rails are still in operation after the normal service lives expire resulting in considerably high damage rates. In order to monitor and prevent the occurrence of the internal injuries of the rails, nearly 10,000 rail workers are working full-time in charge of flaw detections, preventing the accidents of rail fracture and ensuring railway transportation safety. However, with the rapid development of high-speed railways, existing devices exhibit limitations in many aspects:such as flaw detection precision, accuracy, efficiency and PMB flaw detection, etc. Design and investigation of new detection technologies have become essential and have motivated a significant and increasing body of research work, among which ultrasonic detection technology shows a promising direction in both academia research and industrial applications in the development of domestic railway.In this work, we introduce the advantages of ultrasonic detection technology and its domestic and international development status, and systematic ultrasonic guided waves broken track monitoring system is built up based on LabVIEW. The hardware consists of the ultrasonic generator and ultrasonic probe. The ultrasonic generator excites the ultrasonic probe to generate ultrasonic signals, and forms the waveguide passing through the rail. On the other end of the rail, the guide-wave detection signal is received by a sandwich transducer; the data of signals are received by the PCI9812 data acquisition card and the analog to digital converter at the same time, which it then connected to the computer through PCI interface. The software component is mainly ultrasonic guided waves broken rail monitoring software platform that is designed based on virtual instrument in the Windows operating system. This platform is realized by the underlying driver of PCI9812 to achieve control of the state and parameter settings; design signal processing analysis module to read data in the cache of PCI9812, and then process and analyze the guided wave detection signals. Methods of data processing are then applied, including Fourier transformation to analyze the ultrasonic guided wave detection signal in the frequency domain; FIR filter to filter the ultrasonic guided wave detection signal with FIR filter processing windowing with the use of different windows; and the threshold method to monitor the amplitude rail guided wave signal in real-time. Finally, the data through the TCP/IP network communication program is monitored continuously in real-time and is transmitted to the client by the server.With the use of the proposed ultrasonic guided waves broken track monitoring system, the signals are processed according to the rail waveguide transducer generating the signal characteristics; comparisons on complete and broken tracks are carried out revealing changes in the signal characteristics before and after the rail breaking. This study lays a solid foundation in the industrial realization of rail health monitoring. |
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