### ASA 124th Meeting New Orleans 1992 October

## 5pPA6. Elastic scattering at various incidences by a thin cylindrical
shell bounded by hemispherical endcaps.

**Bertrand Dubus
**

**
Antoine Lavie
**

**
**
*Dept. d'Acoust. I.E.M.N., U.M.R. C.N.R.S. 9929, Inst. Superieur
d'Electron. du Nord, 41 boulevard Vauban, 59046 Lille Cedex, France
*

*
*
**Dominique Decultot
**

**
Gerard Maze
**

**
**
*Univ. du Havre, Place Robert Schuman, 76610 Le Havre, France
*

*
*
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(less than or equal to)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.]