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Caractérisation Ultrasonore de Plaques Viscoélastiques Homogènes et Composites

Abstract : We propose to develop an experimental and numerical method capable of evaluating simultaneously the acoustic and geometrical properties of homogeneous viscoelastic plates. In this study, we take into account the fact that the attenuation of ultrasonic waves in this type of materials presents a dispersive character as propagation velocity. To realize this, we selected to study the transmission coefficient of a plate immersed in a fluid (water or air), by taking into account the dispersive (Szabo's model) and dissipative (power law) effects of waves in the plate and implementing them within the theoretical model. We included a correction of diffraction as an approximation to account for the finite size effects of the source. The theoretical model selected represents one of the key elements necessary for the creation of an inverse method devoted to the identification of the elastic and dissipative properties of viscoelastic materials. The other fundamental features of this method are the normally incident measurement transmission coefficient of the plate, as well as the optimization routine. We developed two measurement techniques which are based upon an immersion method or an air-coupled system to measure the frequency response transmission of the plate under investigation. The identification routine developed under Matlab® modifies the input parameters of the numerical model until a response close to the experimental data is obtained, by using a minimization algorithm for nonlinear least squares. The properties extracted simultaneously are : thickness and density, as well as the velocity and attenuation of longitudinal waves in the plate. The procedure has been applied to several polymer materials, then to composite plates (aged or not). We verified that for all of these plates, the thickness and velocity are generally correctly identified. Density is identified with a lower accuracy. Regarding attenuation, we highlighted that it estimation is more difficult, in particular for the attenuation coefficient. However, we obtained accurate results for the identified attenuation exponent. We could observe that the residual error between the experimental and identified models was of the order of 0.5% and 5%, for measurements in water and air, respectively.
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Contributor : Abdelhak El Mouhtadi Connect in order to contact the contributor
Submitted on : Tuesday, May 22, 2012 - 9:59:30 AM
Last modification on : Tuesday, October 19, 2021 - 5:34:13 PM
Long-term archiving on: : Thursday, August 23, 2012 - 2:28:38 AM


  • HAL Id : tel-00699973, version 1


Abdelhak El Mouhtadi. Caractérisation Ultrasonore de Plaques Viscoélastiques Homogènes et Composites. Acoustique [physics.class-ph]. Université du Havre, 2011. Français. ⟨NNT : ⟩. ⟨tel-00699973⟩



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