Accession Number : ADA308651

Title :   The Influence of Geometric Imperfections on Nonlinear Vibrations of Circular Rings.

Descriptive Note : Technical rept.,

Corporate Author : TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS

Personal Author(s) : Till, Paul D.

PDF Url : ADA308651

Report Date : 02 FEB 1995

Pagination or Media Count : 111

Abstract : Circular rings are a common, important component in aerospace and marine structures. Investigating the linear and nonlinear vibrations, as well as the transfer of energy in the wavenumber domain, of these structures is essential to understanding their acoustic radiation characteristics. Analytical, numerical, and experimental examinations were performed to address these issues. The analytical study showed that the inclusion of nonlinear features provides for the nonlinear transition of energy from higher order wavenumber responses to lower order wavenumber responses. Also, the presence of imperfections enhances the nonlinear, quadratic features of the response as well as provides for additional energy transfer to low order wavenumbers, now due to linear coupling. The numerical simulation verifies these results. A higher order spectral processing function, the bicoherence, was used to detect and quantify the quadratic features of the simulated response. In the experimental phase of the study, the response of two rings of different thickness to radius ratios and imperfection compositions were tested. The rings were spatially sampled and the data collected was wavenumber filtered such that the response of each wavenumber was extracted. The experimental results submit evidence of the transfer of energy from higher wavenumber responses to the n=O wavenumber response. Also, as indicated by the bicoherence, quadratic features of the n=O wavenumber response are enhanced by the presence of imperfections.

Descriptors :   *VIBRATION, *ACOUSTIC WAVES, *ACOUSTIC SIGNALS, MATHEMATICAL MODELS, SIGNAL PROCESSING, COMPUTERIZED SIMULATION, ACOUSTIC DETECTION, ENERGY TRANSFER, POWER SPECTRA, SHELLS(STRUCTURAL FORMS), NONLINEAR SYSTEMS, STRUCTURAL RESPONSE, APPROXIMATION(MATHEMATICS), DATA REDUCTION, SOUND TRANSMISSION, PARTIAL DIFFERENTIAL EQUATIONS, QUADRATIC EQUATIONS, NONLINEAR ANALYSIS, ACOUSTIC FILTERS, RINGS, ACOUSTIC SCATTERING, ACOUSTIC DATA, SOUND PRESSURE, FREQUENCY RESPONSE, DISCRETE FOURIER TRANSFORMS, ACOUSTIC FIELDS, ACOUSTIC RESONANCE.

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE