Date of Award

Spring 1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Gene Hou

Committee Member

Raymond G. Kvaternik

Committee Member

Samir R. Ibrahim

Committee Member

Jen K. Huang

Abstract

In this work, structural modification and synthesis techniques based on component mode synthesis are presented. The component mode synthesis method formulates the eigenvalue equation of an entire structure in terms of the vibration characteristics of individual components in the assembly. Through this functional relationship, the individual components are successfully treated as the design entities in the proposed methodology. Unlike conventional design modification techniques that can only treat the properties of the finite elements as the design variables, this technique uses the vibration and static responses of the individual components as the design entities. The sensitivity derivatives of the global responses with respect to the responses of the components are calculated to determine the contribution of each component to the vibration of the global structure.

The structural synthesis is formulated as an integer programming problem that treats the various choices of the components as the design variables; this problem is then solved with a genetic algorithm. After the required responses of the individual components have been obtained, the component mode synthesis method provides an efficient means of repetitively analyzing the global structure for the possible combinations of the assembled structure.

A structural modification technique called local vibration targeting is developed for the efficient modification of the structures. This method finds the most significant components in an assembly and determines the optimal values for their vibration and static responses to obtain the desired change in the performance of the global structure. These particular components are modified locally to achieve the target values. In this study, a linear programming technique is used to determine the target values for the individual components; gradient-based optimization techniques are used for the local design modification. Finally, a two-stage iterative design optimization scheme is developed to handle the local vibration targeting more rigorously. The developed methodologies are successfully demonstrated with two sample problems, and the numerical issues involved in the implementation are discussed.

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DOI

10.25777/demy-ng94

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