Russian Journal of Nondestructive Testing

, Volume 48, Issue 11, pp 649–661 | Cite as

Instantaneous frequency estimation used for the classification of echo signals from different reflectors

Acoustic Methods

Abstract

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.

Keywords

instantaneous frequency normalized frequency deviation reflectors signals flaw shape 

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Copyright information

© Pleiades Publishing, Ltd. 2012

Authors and Affiliations

  • O. V. Nemytova
    • 1
  • A. B. Rinkevich
    • 1
  • D. V. Perov
    • 1
  1. 1.Institute of Metal Physics, Ural DivisionRussian Academy of SciencesYekaterinburgRussia

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