Propagations of Locally Resonant Modes in a Phononic Plate Consists of Periodic Membranes
Date Issued
2009
Date
2009
Author(s)
Sun, Che-Yuan
Abstract
In this thesis, we demonstrate the existence of complete band gaps and the propagation of locally resonant modes in a phononic plate with periodic membranes both numerically and experimentally. In order to understand the influence of the membrane on the dispersion relations, a series of numerical calculations are conducted with the finite element (FE) method. Numerical simulated results show that the dispersion of a phononic plate with periodic membranes can be considered as a superposition of the dispersion of air/steel phononic plate and the resonant frequencies of circular membrane. Besides, in specific bands of locally resonant modes, we found that the group velocity of the modes can be as low as one order of magnitude smaller than that of the A0 mode in a homogeneous flat steel plate of the same thickness. Furthermore, we discussed the mechanism of the slow velocity of the membrane modes in such a structure.n the experiment side, we use a pulsed laser to generate broadband elastic waves and optical devices to detect wave signals. The experimental results are in good agreements with the numerical prediction. Moreover, the slow velocity inside the phononic band gap is observed by using the wavelet transformation, and the results are corresponding to the velocity of the stationary phase point. inally, according to the numerical simulations and experimental results in this thesis, the intense out-of-plane resonances and the slow velocity can be applied to reduce the length of the delay line and enhance the absorbing rate of the catalyzer in the acoustic wave sensor.
Subjects
Phononic crystal
Lamb wave
Finite element method
Band gap
Local resonance
Slow group velocity
Wavelet transform
Type
thesis
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