Elastic scattering at various incidences by a thin cylindrical shell bounded by hemispherical endcaps

Abstract

The elastic scattering by a thin shell cylinder bounded by hemispherical endcaps is analyzed using a coupled finite element–boundary element method (ATILA and EQI codes). The target is made of steel and filled with air. The ratio of the inner radius b to the outer radius a is 0.97. The ratio of the total length L to a is 4. Axial, normal, and oblique incidences are considered for ka≤10 (k is the acoustic wave number in the fluid). The displacement field of the scatterer, the radiated and scattered pressures in the near field and far field, and the directivity patterns are provided. From these results, the peaks in the backscattered pressure are correlated to resonances of the structure and flexural or extensional waves propagating in the solid. Computed results are compared to experimental data obtained with the same target immersed in water. These results are performed by the quasiharmonic method M.I.I.R. (method of isolation and identification of resonances). This method allows one to obtain backscattered pressure spectra and patterns. [Work supported by D.R.E.T. Paris.]