### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 4pPAb12. Structural and acoustic responses of mass-spring loaded elastic
cylindrical shells: Numerical implementation.

**Jin-Meng Ho
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*SFA, Inc., 1401 McCormick Dr., Landover, MD 20785
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Naval Res. Lab., Washington, DC 20375
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An important step in dealing with the mass-spring loaded cylindrical shell
is to evaluate the total shell displacements at the attachment points, which
determine the strength of the equivalent forces. Through dynamical balance at
such points, these displacements satisfy a system of linear equations whose
coefficients involve the shell displacements generated by on-surface forces of
unit strength, a Green's-function problem with both source and observer located
on the shell surface. It is thus evident that flexural waves, though subsonic,
must be accounted for in the ray acoustic solution to the latter problem.
Numerical examples show that they produce high Q intense resonances because of
their extremely small radiation damping, which would be dominated by structural
damping for dissipative shell material, imprinting their signature in the far
field through radiation of the induced forces and carrying much of the
information on the internal load. By including the flexural as well as membrane
waves, the ray model accurately predicts the induced forces, the shell
displacements, and the surface and far-zone pressures in the frequency range of
interest; 1(less than or equal to)ka(less than or equal to)25 (where k is the
fluid acoustic wave number and (alpha) is the shell mean radius). [Work
supported by ONR.]