Ultrasonic modeling of a viscoelastic homogeneous plate

Abdelhak El Mouhtadi (1) , Jean Duclos , Hugues Duflo (1)

1 LOMC - Laboratoire Ondes et Milieux Complexes

An ultrasonic method for determination of acoustical and geometrical properties of a viscoelastic plate immersed in a known fluid (water) is presented. The method utilizes plane longitudinal waves that are normally incident upon a homogeneous plate with attenuation obeying a frequency power law and dispersion described by Szabo’s model. It requires only the knowledge of the fluid properties and recording of two chirps: one without and one with the specimen inserted between the transmitting and receiving transducers. The transmission coefficient of the plate is measured and compared to the predicted one, in which the diffraction of waves emitted by the transducer is taken into account. An inverse scheme based on a nonlinear least squares algorithm allows then simultaneous determination of the plate thickness, density, attenuation (longitudinal) and phase velocity at a given frequency. The technique involves an estimation of standard errors of parameter estimates. An example is given and discussed for a Plexiglas plate. It is shown that thickness and velocity are estimated with a good accuracy ($10^{-3}$). Density is estimated also with a reasonable accuracy ($10^{-2}$), whereas estimated attenuation is less precise.

Mots clés: Viscoelastic plate; Transmission coefficient; Inverse scheme; Standard error

Domaines: Acoustique [physics.class-ph]

Abdelhak El Mouhtadi, Jean Duclos, Hugues Duflo. Ultrasonic modeling of a viscoelastic homogeneous plate. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810700⟩