Michael Klausbruckner
Matthew Conti
Ira Dyer
J. Robert Fricke
Dept. of Ocean Eng., MIT, Cambridge, MA 02139
Previous investigations have examined the backscatter from empty and
internally loaded shells with no damping treatment, demonstrating the primary
importance of helical shear waves. The helical waves contribute to large
backscatter for aspect angles within 30 deg of normal for the empty shell. The
region increases to 45 deg of normal for the internally loaded shells. A
constrained layer was applied to the cylindrical section of an internally
loaded shell to damp the helical waves while decoupling them from the internal
structures. The intended effect was to lower the backscatter levels and reduce
the angular width of strong backscatter to within 30 deg of normal. This
preliminary investigation demonstrates the achievement of each of these goals.
In addition, the importance of direct acoustic backscatter from the attachment
locations of the internal rings was highlighted. The bistatic measurements were
conducted over a frequency range of 2.5