Acoustic scattering from complex elastic shells: visualization of S0, A0 and A waves

Acoustic scattering phenomena from complex immersed elastic shells are studied by high-speed Schlieren visualization for spark-generated spherical quasi-Dirac excitations. The situations considered are air-filled cylindrical shells under normal insonification and air-filled cylindrical shells soldered at one end with a hemispherical endcap under axial and non-axial incidences. The results are compared with those provided by the Methode d'Isolement et d'Identification des Resonances (MIIR) method and corresponding analytical theoretical solutions. The combination of these complementary approaches better highlights some of the behaviors of the symmetric S0- and antisymmetric A0-Lamb waves, as well was the Scholte-Stoneley A-wave, on the considered targets. In particular, the influence of the internal solder inhomogeneities on the creation and/or the conversion of these modes is demonstrated.