Dissertation > Aviation, aerospace > Aviation > Aero-engine ( propulsion system )

Application Research of Procession and Analyses Methods for the Aviation Components Ultrasonic Testing Signal by Wavelet Transform

Author YuanYingMin
Tutor WenWeiDong
School Nanjing University of Aeronautics and Astronautics
Course Aerospace Propulsion Theory and Engineering
Keywords aviation component ultrasonic testing signal wavelet analyses the best wavelet wavelets package
Type Master's thesis
Year 2002
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Wavelets technology and wavelet packages technology for the ultrasonic testing signal of some aeroengine.turbine vane and some aeroplane main undercarriage wheel-hub axes are researched.The ability of checking out flaw in the ultrasonic testing is so worse because of the noise signal. But at present, the ultrasonic signal processing methods are only frequency spectrum analyses based on Fourier transform. So it is difficult to analysis the time characteristic and frequency characteristic at one time. The wavelet’s characteristic of focus’ varieties make wavelet better analyses ability in the time field and the frequency field. It is a perfect method of analyzing non-steady signal, and it is fit to analysis ultrasonic pulse echo signal. The applications of wavelets analyses in the ultrasonic testing signal become a very promising development route. But now the field is finite that wavelet analyses is used in the ultrasonic testing signal processing, and the problem of selecting the best wavelet didn’t be considered in the application of wavelet. Now the research reports are also lack about the application of wavelet analyses in processing aviation component ultrasonic signal.A collecting scheme of ultrasonic testing signal about turbine vane and wheel-hub axes is given, and ultrasonic testing signals of two kinds of component are collected by tesing. And wavelet and wavelet package methods are presented to process and analysis the collected signal. The effect is better. The applications of many kinds of wavelets in the ultrasonic signal of turbine vane and wheel-hub axes are compared in discomposed effect, running speed, avoiding noise and the composition of signal. The selecting principles of wavelets applying for the aviation component ultrasonic signal processing are given. That the wavelet db4 and wavelet packages db4 are the ideal methods in analyzing the aviation component ultrasonic testing signal is validated.

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