### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 4pSAb2. A modal/spectral analysis of mass distribution effects in a
fluid-loaded plate.

**John Babish
**

**
Jerry H. Ginsberg
**

**
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*School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332-0405
*

*
*
Feit and Johnson [ 2309(A) (1991)] showed that the signal
scattered by a plate is greatly affected by the spatial distribution properties
of an attached mass. Ginsberg et al. [ASME Proc., paper 93-WA/NCA-20 (1993)]
used the surface variational principle (SVP), which describes the surface
pressure and displacement as a set of interacting waves, to examine a
fluid-loaded plate with attached point mass in an infinite baffle. In their
analysis the mass distribution was represented as a Fourier series in an effort
to determine how coarse the model could be, and still accurately represent the
direct point mass solution. Their conclusion was that a series length of eight
terms is adequate to describe the system behavior in the frequency range
kL(less than or equal to)3, but a series of fewer than six terms is
substantially inaccurate. The current work uses the in-vacuo modes of the
spectrally smoothed mass--plate system as Ritz functions for displacement. The
solution in terms of these modes is compared to the results obtained from the
Fourier series representation, in order to identify why a critical number of
terms is required for the spectral description of mass distribution.