ANALYTICAL EVALUATION OF MODAL LOSS FACTORS AND RADIATION EFFICIENCY FOR RECTANGULAR PLATES

Abstract

In this thesis, an analytical formulation of the modal loss factor has been done for the case of simply supported rectangular plate subjected to a point harmonic force of constant frequency.An attempt has been made to seeka generalisation for the internal damping of the plate for which the material damping constants J and N are known. Effects of changes in aspect ratio, thickness, material damping constants, and point force location on the modal damping for both the constant force and the constant amplitude excitations have been studied.The higher order modal damping has been correlated.with.the fundamental mode value in each case. Loss factors when the plate vibrates under complex resonance condition (more than one mode under simultaneous resonance) have also been evaluated. Thus the dependence of modal damping values on the different point excitations has been quantified. Fundamental mode loss factors have been evaluated for the plates with different combinations of simply supp-orted and clamped edge conditions. Damping of a simply supported plate with thickness variation in one direction has been obtained with the help of Galerkin's method. Thickness variatiornof linear and parabolic type have been considered and the loss factor in each case has been correlated with that of uniform thickness ease.