Accession Number : AD0769243

Title :   Nonlinear Dynamics by Mode Superposition.

Descriptive Note : Technical rept.,

Corporate Author : BROWN UNIV PROVIDENCE R I DEPT OF ENGINEERING

Personal Author(s) : Nickell,Robert E.

Report Date : AUG 1973

Pagination or Media Count : 59

Abstract : A mode superposition technique for approximately solving nonlinear initial-boundary-value problems of structural dynamics is discussed and results, for examples involving large deformation, are compared to those obtained with implicit direct integration methods, such as the Newmark generalized acceleration and Houbolt backward-difference operators. The initial natural frequencies and mode shapes are found through inverse power iteration, with the trial vectors for successively higher modes being swept by Gram-Schmidt orthonormalization at each iteration. The subsequent modal spectrum for nonlinear states is based upon the tangent stiffness of the structure and is calculated by a subspace iteration procedure that involves matrix multiplication only, using the most recently computed spectrum as an initial estimate. The results indicate that a number of important advantages accrue to nonlinear mode superposition. (Modified author abstract)

Descriptors :   (*Structural mechanics, Nonlinear systems), Plastic deformation, Nonlinear differential equations, Partial differential equations, Numerical integration

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE