Research On Phononic Crystal Enclosures

As an artificial periodic material/ structure that can regulate the propagation of elastic waves,phononic crystals have attracted wide attention of researchers.In this paper,based on the bragg and the local resonance band gap mechanisms,the bragg and locally resonant hemispherical,rectangular and combined sound insulation cover models of phononic crystal are constructed,the transmission mechanisms and sound insulation properties of acoustic wave(elastic wave)in structure field and acoustic-solid coupling field of these sound insulation covers are studied.The main contents include:1.Based on the bragg phononic crystal mechanism,the bragg hemisphere shell and rectangular enclosures structure are designed respectively,the acoustic-structure coupling dynamic equations of these two kind of bragg type insulation covers are established according to the acoustic-structure boundary coordination condition.The conception of variable vector generalized periodicity is introduced,and with the help of Bloch theorem,the acoustic-structure coupling properties under the excitation conditions of center and bias point sound source are analyzed,and the influence of the corresponding parameters is investigated.2.According to the local resonant phononic crystal mechanism,the local oscillator configuration suitable for the local resonant hemispherical shell and the single cell configuration suitable for the rectangular sound enclosure are designed respectively,the two kinds of local resonant enclosure are constructed.The acoustic properties under the radiation conditions of the internal center and bias point sound source are analyzed by the finite element method.By comparing the band structure of the single cell,the attenuation effects of radial and bending vibration are studied,and the influence of the main parameters is investigated.3.The bragg type and local resonant type combined sound insulation covers consisting of hemispherical shells and cylindrical shell are constructed respectively,and the sound insulation characteristics are studied.The results show that there are significant band gap behaviors in the hemispherical shell,rectangle and combined acoustic enclosures based on the two kinds of mechanisms.Through reasonable control and design of the structure and material parameters of the sound insulation covers,the bragg type sound insulation cover can effectively restrain the sound radiation under the internal sound source in the middle-high frequency range,while the local resonance type sound insulation cover can achieve better sound insulation performance in the middle-low frequency range.