## 3aSAb2. Precise formulation of the vibroacoustic effects of an added constrained damping layer on a plane structure.

### Session: Wednesday Morning, May 15

### Time: 11:00

**Author: Jean Nicolas**

**Author: Noureddine Atalla**

**Author: Olivier Foin**

**Author: Bertrand Mercier**

**Location: Mech. Eng. Dept., Univ. de Sherbrooke, Sherbrooke, PQ J1K 2R1, Canada**

**Abstract:**

The model proposed here describes the SAV behavior of a sandwich plate
(elastic--visoelastic--elastic) and uses the following hypothetisis, inspired by
the discrete layer theory: The viscoelastic layer takes into account bending,
shear, and traction compression; normal strain and torsional motion are
neglected; using the continuity of the displacement at the visoelastic layer
interfaces, the displacement field of the viscoelastic layer is written as a
function of the elastic layer displacement field. A variational method is used
to find the displacement equations. The radiation impedance is calculated via a
formulation recently proposed by Atalla and Nicolas [J. Acoust. Soc. Am.
(1994)]. This formulation allows one to calculate, for a large frequency range,
the quadratic velocity, the radiation efficiency, and the radiated power.
Emphasis is then put on precise experimental validation. A fully instrumented
setup using a laser vibrometer for probing the displacement field has been
developed. The basic plate is made either from aluminum or from resin epoxy.
Using technical data furnished by the manufacturers, the comparison between
theory and experience is extremely good in the case of aluminum. Discrepancies
are bigger for the resin epoxy and this aspect will be discussed. Partial
covering, which is also of great practical interest, will also be presented for
both theoretical and experimental aspects.

from ASA 131st Meeting, Indianapolis, May 1996