Parametric Instability of Elastic as well as Viscoelastic Sandwich Beam Configurations in Temperature Environment

Abstract

The structural or the machine members which are to have high strength to weight ratio newlineand to work in high temperature environment subjected to parametric vibration under axial newlinepulsating load are made of sandwich beams with viscoelastic core. The middle layer is newlineviscoelastic layer whose main function is to increase the damping capacity of the beam, hence newlineto increase the stability of the system and also to decrease its weight simultaneously due to its newlinelow density. The upper and lower layers are elastic layers and generally the lower layer is newlinethicker than the upper layer. In this dissertation first stability study has been done for uniform newlineasymmetric sandwich beam and with uniform thermal gradient. The effects of various newlineparameters such as thermal gradient, modulus ratios, elastic foundation parameter and newlinegeometric parameters on the non-dimensional buckling loads for static condition, natural newlinefrequencies and on the zones of instabilities have been studied for pinned-pinned, clampedpinned newlineand clamped-clamped end conditions. Second chapter meant for the parametric newlinestability study of tapered asymmetric sandwich beam lying on a variable Pasternak foundation newlinewith uniform temperature gradient. Then the same system is reduced to a linearly tapered newlinesymmetric configuration and later it is modified to exponentially taper asymmetric newlineconfiguration with variable thermal gradient, as the system is in steady state heat flow newlinecondition and the cross-section is changing along the longitudinal direction. Before newlineconsideration of variable thermal gradient, the consideration of uniform thermal gradient was newlinebeing used even for tapered beam as used by Kar and Sujata. But author of this work has newlinesuggested that the variable thermal gradient is more justified than uniform thermal gradient in newlinecase of tapered beam configuration and hence the research has been carried out both for newlineuniform as well as variable thermal gradient. The effects of various geometric parameters and newlinematerial properties on the system stabilities have been investigated.