Instantaneous frequency estimation used for the classification of echo signals from different reflectors
A comparative analysis of the frequency parameters of echo signals from artificial reflectors of different shapes and from a natural spill-type flaw has been performed. The use of the instantaneous frequencies of ultrasonic signals that correspond to certain instants inside a pulse was suggested as an informative parameter for determining the flaw type. Instantaneous frequency is estimated based on the algorithm of the continuous wavelet transform, which increases the noise immunity of the method. It is shown that for the algorithm to be practically implemented it is appropriate to present the results in the form of dimensionless parameters, namely, normalized frequency deviations determined between the pulse center, edge, and tail. Their joint application makes it possible, in particular, to reliably distinguish echo signals that are reflected at junction flaws that rise to the surface of a test object (notches, dihedral angles, and spills of the weld joints), flat specimen surfaces, and local flaws, such as cylindrical side through holes and flat bottom drills.
Keywordsinstantaneous frequency normalized frequency deviation reflectors signals flaw shape
Unable to display preview. Download preview PDF.
- 1.Shcherbinskii, V.G. and Belyi, V.E., A New Informative Parameter of the Flaw Nature upon Ultrasonic Testing, Defektoskopiya, 1975, no. 3, pp. 27–36.Google Scholar
- 2.Whittaker, I.S. and Iessop, T.J., Ultrasonic Detection and Measurements of Defects in Stainless Steel, Br. J. Non-Destr. Test., 1981, vol. 23, no. 6, pp. 293–303.Google Scholar
- 3.Gurvich, A.K. and Kuz’mina, L.I., Scattering Indicatrices as a Source of Additional Data on Detected Flaws, Defektoskopiya, 1970, no. 6, pp. 47–56.Google Scholar
- 4.Vopilkin, A.Kh., Difraktsionnye metody v ul’trazvukovom nerazrushayushchem kontrole (Diffraction Methods in Ultrasonic Nondestructive Testing), Moscow: Izd. NTO “Priborprom”, 1989.Google Scholar
- 5.Perevalov, S.P., The Study of Geometrical and Acoustic Characteristics of Erosion Reflectors, Defektoskopiya, 1994, no. 9, pp. 15–31.Google Scholar
- 9.Vainshtein, L.A. and Vakman, D.E., Razdelenie chastot v teorii kolebanii i voln (Separation of Frequencies in the Theory of Oscillations and Waves), Moscow: Nauka, 1983.Google Scholar
- 10.Rinkevich, A.B., Nemytova, O.V., and Perov, D.V., Comparison of Frequency Features of Pulse Echoes from Different Reflectors, ISRN Mech. Eng., 2011, p. 371514.Google Scholar
- 11.Perov, D.V., Rinkevich, A.B., and Kusonskii, O.A., Veivletnyi analiz sverkhdlinnoperiodnykh seismicheskikh ostsillyatsii. Sbornik trudov XVI Sessii Rossiiskogo akusticheskogo obshchestva (The Wavelet Analysis of Super-Long-Period Seismic Vibrations), Moscow: GEOS, 2005, vol. 1, pp. 279–282.Google Scholar
- 13.Perov, D.V. and Rinkevich, A.B., Using the Different Types of Wavelet Transform for Analyzing Acoustic Fields and Signals in Elastic Media. New Research on Acoustics, Weiss, B.N., Ed., New York: Nova Science Publishers, 2008, pp. 65–109.Google Scholar
- 14.Dobeshi, I., Desyat’ lektsii po veivletam (Ten Lectures on Wavelets), Izhevsk: NITs “Regulyarnaya i Khaoticheskaya Dinamika”, 2001.Google Scholar
- 17.GOST (State Standard) 14782-86: Nondestructive Testing. Weld Joints. Ultrasonic Methods.Google Scholar