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

## 4aSA4. Time-domain methods of analysis in structural acoustics.

**P. R. Stepanishen
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*Dept. of Ocean Eng., Univ. of Rhode Island, Kingston, RI 02881
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An overview of the use of time-domain methods to analyze the mechanical
response of fluid loaded structures in vacuo and in fluid is presented. The
response of a single degree of freedom mechanical oscillator will first be
addressed and then used to build the solution to more complex plate and shell
vibration problems using well established time-dependent eigenfunction or
eigenvector expansions. In contrast to the in vacuo problems in which the modal
coefficients are uncoupled convolution integrals, the coefficients for the
fluid-loaded problems are shown to be described by a set of coupled convolution
integral equations. The underlying physics that naturally leads to the coupled
convolution integral equations will be discussed. Direct time-domain methods of
evaluating the convolution integrals and solving the convolution integral
equations will be presented and discussed. Finally, numerical results will be
presented for both in-vacuo and in-fluid plate and shell problems to illustrate
typical response characteristics.