ASA 127th Meeting M.I.T. 1994 June 6-10

1aSA11. Reduction of backscattering from cylindrical shells by damping treatment.

Yueping Guo

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

For oblique incidence within about 30(degrees) off normal incidence, backscattering from cylindrical shells is known to be dominated by reradiation from shear and/or compressional waves in the shell. Thus backscattering can be reduced by dissipating these shell-borne waves through damping treatment to the shell. This paper discusses some possible forms of damping. Three examples are given, namely, a three-layered shell with a homogeneous viscoelastic core, a three-layered shell with a fiber-reinforced viscoelastic layer, and a shell with cavities filled with highly dissipative viscous fluid. It is shown that these kinds of damping treatment reduce the phase speeds of the radiating waves, as well as increase the effective loss of the composite shell, which lead to significant reduction in the backscattered field. [Work supported by ONR.]