Attenuation of pure shear-waves in anisotropic materials: how-to measure it from plane-wave angular spectrum decomposition of the transmitted beam in an immersion tank.
Résumé
In this paper, we first describe an original experimental device, which enables us to isolate shear waves and thus to evaluate their attenuation by a plane-wave angular spectrum decomposition of the transmitted beam. In a second step, we propose a method to characterize the material's stiffness tensor in its complex form, the imaginary part of the elastic constants being a function of frequency. Toward this end, the overall transmission coefficient, including the infinite series of internal reflexions, is calculated in oblique incidence and in immersion using the recursive stiffness matrix method coupled with the Stroh formalism. This modeling was chosen because it showed to be computationally stable and efficient for any anisotropic medium, even beyond the critical angles. Experimental results obtained on orthotropic austenitic stainless steel samples will be presented, and discussed.