DAMPING MECHANISMS GOVERNING PLATE VIBRATION

In this paper we consider the contribution of the different damping me chanisms responsible for vibro-acoustic damping. They are four in numb er that one can regroup according to their contribution: an internal d amping (thermoelasticity and viscoelasticity) and a damping due to the coupling of the structure with the fluid (fluid friction and acoustic radiation). This approach allows to explain more precisely the physic al phenomena in play and to foresee the frequency dependence of the st ructural damping. With particular experimental conditions (metallic pl ates, undissipative boundary conditions, vacuum chamber), we evaluate sound radiation losses, which are very low (in the order of 2 x 10(-3) ) and show that they are generally masked by losses in the material, s upport or assembling (like in a harpsichord).