| Phononic Crystals are a new kind of artificial structural functional material. It has attracted wide attention for its unique characteristics, for example, elastic wave band gap,negative refraction, etc. The researchers have been revealing the basic physical mechanism of phononic crystals and trying to apply it to practical engineering, especially for the beams and plates which are widely used. To sum it, phononic crystals provide a new solution for the control of vibration and noise.The main point of this paper is to analyze the band gap characteristics of phononic crystal beam and acoustic baffle. A profound study has been done in order to reveal how the viscoelastic damping affect the band gap of phononic crystal beam and the sound insulation function of acoustic baffle in the stop band. The contents are as follows:1. The modeling approach of viscoelastic damping is introduced. Then, the relaxation integral constitutive equation which is based on Maxwell model and the Boltzmann theory is given. Apart from that, the generalized Bloch’s theorem that can be used in damping phononic crystals is described.2. A discrete dynamical model of damping phononic crystal beam is built for analyzing the band gap characteristics. In addition, the influence of the damping effect on band gap have been investigated and corresponding simulations are made to validate the conclusions.3. A new kind of acoustic baffle based on the concept of phononic crystals is proposed.The band structure is calculated on the basis of super-cellular method. Meanwhile, the formation mechanism of the band gap is revealed and the optimization for the band gap is performed.Our results show that, the viscoelastic damping has significant effect on phononic crystal beam for that it can adjust the range of the bang gap. Moreover, the phononic crystal acoustic baffle has certain band gap within low frequency range. Comparing with traditional acoustic baffles,it has obvious advantage in stop band in terms of sound insulation quantity. |
