A STUDY ON RESONANT MODAL DAMPING OF RECTANGULAR PLATE OF NON-UNIFORM THICKNESS UNDER HARMONIC AND NON- HARMONIC LOADING

Abstract

In this thesis an analytical formulation of the modal loss factor has been done for the case of simply supported rectangular plate with variable thickness subjected to a uniformly distributed load. Thickness variation is considered as linear thickness variation and parabolic thickness variation in one direction. An attempt has been made to seek a generalisation for the internal damping of the plate for which the material damping properties such as damping constant J and damping exponent N are known. Fundamental mode loss factor have been evaluated for the variable thickness rectangular plate at different aspect ratios, taper parameters, loads and plate thicknesses based on dilatational strain energy dissipation and distortional strain energy dissipation. The plate is subjected to uniformly harmonic loading and non-harmonic loading like periodic square wave and periodic triangular wave. Variation of loss factor for different cases of rectangular plate with variable thickness has been plotted. Loss factors according to dilatational strain energy dissipation and distortional strain energy dissipation give the upper and lower bounds of within which the value of the value of loss factor lies in actual case. In this thesis, error analysis for loss factors of such a plate at different aspect ratios, taper parameters, loads, and plate thicknesses has been done by fourth order polynomial curve fitting, like k1e°+k2e'+k3e2+k4e3+k5e4 where k1 k2, k3, k4 and k5 are polynomial coefficients, under such loadings.