### ASA 124th Meeting New Orleans 1992 October

## 5aSA5. Fluid-loaded elastic slab excited by line and point loads.

**Yuksel Gur
**

**
Patrick Leehey
**

**
**
*Dept. of Mech. Eng., MIT, Rm. 3-262, 77 Massachusetts Ave., Cambridge, MA
02139
*

*
*
The plate equations are not sufficient to predict the response for high
wave-number excitations. In order to determine the difference between plate and
elastic slab results, and the range of validity of the plate equations, the
following problems were solved: an infinite slab excited by a line load and a
point load. The space above the slab contains an acoustic medium and below the
slab there is a vacuum. It was proven that the point-loading case was formally
identical to the line-loading case. The only difference was in the use of
Hankel transforms instead of Fourier transforms. Full elastic slab equations
were solved for this acoustic medium/elastic slab coupling problem with
analytical and numerical techniques. Far-field-radiated pressure and surface
interface displacement results indicated that full elastic slab equations
predict lower radiated pressure and higher interface trapped wave amplitude
compared to thin plate results for high-frequency excitations. The upper
nondimensional frequency limit for the validity of the thin plate equations was
determined to be (omega)h/c[sub l](approximately equal to)0.17. By introducing
structural damping, one is able to determine the interface displacements in the
vicinity of the excitation. [Work supported by Mechanics Division, ONR.]