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.