Caracterisation ultrasonore d'un materiau elastique a partir de I'analyse de I'image temps-frequence de Wigner-Ville

摘要

Spectral analysis is a powerful tool for processing stationary signals. When applied to transient phenomena or non stationary signals, the time-frequency methods (Wigner-Ville distribution, Wavelts or Spectrograms) have certain advantages. This paper presents methods of using the Wigner-Ville transform for the characterization of the bachscattered acoustic signals by an elastic tube. In this article, the time-frequency representation of Wigner-Ville is used to analyse the experimental acoustic signal backscattered by a thin elastic tube of radii ratio equal to 0.9. The characterization of the material elastic (tube) can be done on the basis of its reduced cut-off frequencies of circonferential waves propagating around the tube and of its transversal and longitudinal velocities calculated from the circumferential wave. The time-frequency analysis allows to determine the cut-off frequency of the antisymmetric A1 and the symmetric 51 circumferential waves. The transversal and longitudianl velocities of aluminum estimated from the time-frequency image of Wigner-Ville are in good agreement with those measured by the classic experimental methods given in the scientific literature.