Simplified Method of Analysis of Structural Vibrations of Asymmetric Rockets

概要

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A simplified analytical method is proposed to obtain eigenfrequencies and modes of a rocket with an asymmetric configuration. This method is an extension of the symmetric beam element matrix method and utilizes asymmetric beam elements. The purpose of this simplified analysis using a FORTRAN 77 program is to prepare an analytical tool for the preliminary design phase and a rough-check tool for detailed analysis. This program has three functions : (1)to generate stiffness and mass matrices for the asymmetric beam element using Timoshenko-type beam theory, (2)to calculate the dynamical matrix from which rigid body degrees of freedom are eliminated, and(3)to calculate eigenvalues and eigenvectors. A sample analysis of the structural vibrations in a hypothetical rocket with an asymmetric configuration is conducted to demonstrate the capability of this simplified method. The results obtained agree well with those obtained by MSC / NASTRAN analysis, and this proposed method greatly simplifies the preparation of a model. Based on these findings, the proposed method is judged to be an efficient tool for the analysis of structural vibrations in an asymmetric rocket.
1998-12-15