The Research Of Time-Frequency Characteristics Extraction Of Steel Corrosion Acoustic Emission Signal

At present, large oil storage tanks are widely used in the oil industry, so the safety production and operation of the tank is very important. Due to the chemical nature of oil and some other factors, the corrosion of tank bottom is the most common problem in tank accidents. In detection of tank bottom, compared with the traditional nondestructive testing methods, the acoustic emission detection has the advantages of no need opening the tank, low detection cost, small detection risk, etc., and is an ideal method for the detection of the oil storage tanks in service.Most time frequency feature extraction methods such as STFT,ST and WVD,has the disadvantage of low resolution or inaccuracies.Fractional S transform combines the advantage of S transform and fractional Fourier transform: ST in signal’s high frequency band by narrow window and obtain better time resolution, low frequency using the wide window,obtain better frequency resolution; With optimal matching order which is the corresponding order of the fractional Fourier transform’s maximum peak value,fractional Fourier transform can get a better fractional time-frequency representation by rotating the fractional frequency axis to the right place.In this paper, the basic theory of fractional S transform and several main parameters are discussed. The selection method of the rotation factor a, Gauss window function adjustment factor p and q, and their influence on the time frequency aggregation and accuracy of fractional S transform are studied and discussed. The simulation results shows that the fractional S transform is more suitable for the time-frequency feature extraction of AE signals than the S transform in time-frequency clustering and precision.At last, the time-frequency characteristics of Corrosion AE signals are analyzed by using the fractional S transform, and the related features of different signals are given.