| Rail is an important integral part of rail transport and broken rail will cause the derailment, overturning and other major traffic accidents. Especially with the recent development of China’s high-speed railway, railway transportation need to meet higher standards. Cracks or breaks in the rail must be detected in time in order to ensure the safety and smooth flow of rail transport. So the research on broken track monitoring system is necessary. Due to the characteristics and advantages of ultrasonic testing, we can monitor the health of rail all the time to ensure the safety of train.When the ultrasonic wave reflected several times in the media with limited edge (such as:bars, rods, etc.), it will form the ultrasonic guided wave. Comparing with common ultrasonic wave, ultrasonic guided wave has some different characteristics such as long propagation distance, dispersion and multi-modes. Virtual instrument technology was proposed by the United States National Instruments in the1980s, based on a combination of hardware and software on the use of graphical programming. The technology is more easily and intuitively comparing to traditional programming languages. The core of the technology is software designing. So the virtual instrument has a good adaptability, can quickly and easily change the software based to meet all kinds of requirements.According to the research objectives and methods in this paper, an ultrasonic guided waves broken track monitoring system is set up based on laboratory equipment. The hardware is consisted of an ultrasonic generator and a modal hammer, used to generate ultrasonic, in the other end of the rail guide-wave detection signal is received by PCB352C33and R3a acoustic emission sensor. PCI9812data acquisition card receive the data of signal and analog to digital converter at the same time. Then it connected to the computer through PCI interface. Software components:an ultrasonic guided waves broken rail monitoring software platform is designed based on virtual instrument in the Windows operating system. This platform designed by calling the underlying driver of PCI9812to achieve control of the state and parameter settings; and designing signal processing analysis module to read data in the cache of PCI9812, and then processing and analysis the guided wave detection signal. Finally, methods of data processing: Fourier transform is used to analyze the ultrasonic guided wave detection signal in the frequency domain; FIR filter is used to filter the ultrasonic guided wave detection signal with FIR filter processing windowing and use different window; short time Fourier transform is used to analyze the ultrasonic guided wave detection signal in the time and frequency domain; wavelet transform, analyze the ultrasonic guided wave detection signal in the time and frequency domain, and then use the threshold method (soft and hard threshold) to denoise the ultrasonic guided wave detection signal.Finally we can build up an ultrasonic guided wave broken track monitoring system, based on virtual instrument, by combining the hardware platforms and software system to achieve the monitoring of the health of the rail. |
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