Experimental Research On Nonlinear Vibrations Of Flexible Beam And Plate

Flexible beam and plate structures have been increasingly used in fields of aerospace and civil engineering. Correspondingly, more and more requirements of reliability, precision and stability become considered due to the special characteristics of these structures such as light aromatics and flexibility. Research on the dynamics and vibration control of these structures, therefore, are of great importance. Nonlinear vibration, bifurcations and chaotic dynamics play an important role in nonlinear science. Specific researches on nonlinear dynamics of mechanical flexible structures can provide essential theoretical guidance for their design and control in engineering applications.In this paper, nonlinear dynamic characteristics of flexible cantilever beam with square section, metallic plate and Composite Laminated Plate have been investigated in detail using experimental method. The main contents are as follow:1. For cantilever beam, the case with harmonic parametric excitation has been maily discussed with the following details:1) Natural frequencies obtained mathematically have been compared with those of experiments, by which sub-harmonic and super harmonic resonance has been found;2) Translating processes between different mode orders and mode directions have been researched experimentally. Frequency and amplitude response curves have been drawn based on the observed points. Nonlinear character of sensitivity toward initial values has been studied and regareded to cause the curves;3) Chaotic phenomena as a result of interaction of different modes have been studied. In resonant zones, two kinds of multi-mode combination have been found; two correspongding kinds of pulse jumping phenomena have been observed as well;4) Relative damping coefficients have been determined experimentally.2. With regard to rectangular thin plates, influences from geometric dimension, boundary conditons and kinds of excitations have been studied with the details as follow:1) By means of theoretical calculation and finite element imitaiton, natural frequencies and modes have been obtained;2) Resonant frequencies have been obtained using hammering method and frequency sweeping method. Effects from boundary conditons and excitions have been discussed;3) A kind of low frequency mode resonance has been found.