Modeling Techniques for Sonic Fatigue Prediction
Report Number: AFFDL TR 65-171
Author(s): Wang, P.
Corporate Author(s): North American Aviation, Inc.
Laboratory: Air Force Flight Dynamics Laboratory
Date of Publication: 1966-06
Pages: 140
Contract: AF 33(615)-1743
DoD Project: 1471
DoD Task: 147101
Identifier: AD0648078
Abstract:
The principles of static and dynamic similitude were applied to typical complex structural components for the purpose of examining the application of modeling techniques to sonic fatigue predictions. Modeled specimens of curved panels, honeycomb sandwich flat panels, and honeycomb sandwich cantilever beams have been tested. The tests were conducted on full scale 5/8, and 3/8 size models. The tests and analyses demonstrated that scale reductions of linear panel dimensions, and other size factors necessary in the fabrication of models, may be separately considered in maintaining the established similitude relationships. Both random spectra and discrete frequency acoustic excitation are considered. Stress correlation is the critical parameter in modeling for acoustic fatigue. True models with exact geometric scaling in all elements are not necessary. Adequate modeling is obtained by maintaining the same aspect ratio and modes for the specimen and model. The frequency and stress then vary at predetermined magnitudes with a functional relationship to damping, amplitude, and cross-section (thickness) geometric parameters. Non-linear effects are dependent on excitation levels. In general, a prerequisite to sonic fatigue tests is a knowledge of the non-linearity induced by damping and amplitude for each specimen. The experimental data confirms the application of basic procedures formulated by Miles, Palmgren, and Miner which minimize the requirement for random excitation in the use of modeling techniques for sonic fatigue predictions.
Provenance: Lockheed Martin Missiles & Fire Control
Author(s): Wang, P.
Corporate Author(s): North American Aviation, Inc.
Laboratory: Air Force Flight Dynamics Laboratory
Date of Publication: 1966-06
Pages: 140
Contract: AF 33(615)-1743
DoD Project: 1471
DoD Task: 147101
Identifier: AD0648078
Abstract:
The principles of static and dynamic similitude were applied to typical complex structural components for the purpose of examining the application of modeling techniques to sonic fatigue predictions. Modeled specimens of curved panels, honeycomb sandwich flat panels, and honeycomb sandwich cantilever beams have been tested. The tests were conducted on full scale 5/8, and 3/8 size models. The tests and analyses demonstrated that scale reductions of linear panel dimensions, and other size factors necessary in the fabrication of models, may be separately considered in maintaining the established similitude relationships. Both random spectra and discrete frequency acoustic excitation are considered. Stress correlation is the critical parameter in modeling for acoustic fatigue. True models with exact geometric scaling in all elements are not necessary. Adequate modeling is obtained by maintaining the same aspect ratio and modes for the specimen and model. The frequency and stress then vary at predetermined magnitudes with a functional relationship to damping, amplitude, and cross-section (thickness) geometric parameters. Non-linear effects are dependent on excitation levels. In general, a prerequisite to sonic fatigue tests is a knowledge of the non-linearity induced by damping and amplitude for each specimen. The experimental data confirms the application of basic procedures formulated by Miles, Palmgren, and Miner which minimize the requirement for random excitation in the use of modeling techniques for sonic fatigue predictions.
Provenance: Lockheed Martin Missiles & Fire Control