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

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.