OPTIMUM FREQENCY DESIGN OF CONICAL SHELL STRUCTURES

Abstract

In the last two decademuch effort has been made to develop general analysis procedures for shell structures. As shell structures have comparatively light weight, and high stiffness, strength and load capacity, and are able to cover a large span of space, they have been widely used in aerospace engineering, marine engineering, power plant engineering, and civil engineering.The understanding of their mechanical behavior under static, dynamic, and thermal loads is of considerable importance for arriving at efficient designs of shell structures.

One of the important applications of shell structures is the rocket or airplane exhaust nozzles having divergent or convergent conical configuration. Such structures are subject to dynamic loading and vibrations, which have their origin from the engine boosters and from the pressure fluctuations in the flame. Therefore, adequate study should be performed in their early design stages in order to avoid the occurrence of• excessive vibrations and possible damage caused by fatigue. It is the major aim •of the present study to investigate the natural vibration characteristics of different types of conical shell structures, and build an appropriate design optimization model aiming at the reduction of the overall vibration level without the penalty of increasing structural mass.