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Oct 2007

Volume 122, Issue 4, pp. 1845-EL141

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Rayleigh scattering of acoustic waves in rigid porous media

Claude Boutin

J. Acoust. Soc. Am. Volume 122, Issue 4, pp. 1888-1905 (2007); (18 pages) | Cited 3 times

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This paper describes the long wave scattering effect in gas saturated porous media using the homogenization method. To investigate the deviation from the continuum description, the multiscale asymptotic expansions are developed up to the third order. The leading (zeroth) order leads to the Biot-Allard continuum description. The correction of first order induces nonlocal terms in the dynamic Darcy law and thermal behavior, without modifying the wave characteristics. The correction of second order introduces additional dispersion effects on the velocity and attenuation. This theoretical approach is illustrated by analytical results in the simple case of a periodic array of slits.
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43.20.Fn Scattering of acoustic waves
43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
43.20.Jr Velocity and attenuation of elastic and poroelastic waves

Reconstructing the adhesion stiffness distribution in a laminated elastic plate: Exact and approximate inverse scattering solutions

Ricardo Leiderman, Paul E. Barbone, and Arthur M. B. Braga

J. Acoust. Soc. Am. Volume 122, Issue 4, pp. 1906-1916 (2007); (11 pages)

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This paper formulates and solves a time harmonic inverse scattering problem to reconstruct the effective stiffness distribution of an adhesive bond in a layered elastic plate. The motivation is based on the assumption that localized adhesion flaws that diminish bond stiffness also tend to diminish bond strength. The formulation is based on the invariant imbedding method, applies to isotropic and anisotropic elastic layers, and is essentially that of identifying embedded acoustic sources in elastic layered structures. This paper presents two solutions for the inverse problem: the Born approximation and the exact solution. The example calculations compare the two solutions and show that when imperfections are too large in either magnitude or extent the accuracy of the Born approximation breaks down. The impact of noise and uncertainties in the background properties in the inversion is also investigated. A regularization strategy is introduced in the exact solution that controls solution sensitivity in regions with low signal to noise ratio.
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43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves
43.40.Le Techniques for nondestructive evaluation and monitoring, acoustic emission
43.40.Fz Acoustic scattering by elastic structures
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