Nonlinear Vibrations of Cantilever Beams and Plates
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Experimentally the energy transfer between widely spaced modes is found to be a function of the closeness of the modulation frequency to the natural frequency of the first mode. The modulation frequency, which depends on various parameters like the amplitude and frequency of excitation, damping factors, etc., has to be near the natural frequency of the low-frequency mode for significant transfer of energy from the directly excited high-frequency mode to the low-frequency mode.
An experimental parametric identification technique is developed for estimating the linear and nonlinear damping coefficients and effective nonlinearity of a metallic cantilever beam. This method is applicable to any single-degree-of-freedom nonlinear system with weak cubic geometric and inertia nonlinearities. In addition, two methods, based on the elimination theory of polynomials, are proposed for determining both the critical forcing amplitude as well as the jump frequencies in the case of single-degree-of-freedom nonlinear systems.
An experimental study of the response of a rectangular, aluminum cantilever plate to transverse harmonic excitations is also conducted. Various nonlinear dynamic phenomena, like two-to-one and three-to-one internal resonances, external combination resonance, energy transfer between widely spaced modes via modulation, period-doubled motions, and chaos, are demonstrated using a single plate. It is again shown that the closeness of the modulation frequency to the natural frequency of the first mode dictates the energy transfer between widely spaced modes.
- Doctoral Dissertations