Study On Low Frequency Band Gap Characteristics Of Phononic Crystals And Structural Design

Phononic Crystals are a new type of periodic composite material that can artificially regulate the frequency range of sound absorption in materials,providing a guiding direction for the mute design and vibration reduction design of modern equipment,especially in the fields of defense and aerospace.In this paper,theoretical and experimental studies are carried out on the low frequency band gap characteristics and structure design of phonon crystals.Firstly,the theoretical basis and characteristic parameters of phonon crystals are introduced,and the dispersion relation and transmission characteristics of phonon crystals,as well as the basic characteristics and physical mechanism of locally resonant phonon crystals are summarized and analyzed through examples.Based on this,puts forward a kind of compound resonance local resonance type phononic crystal as the research object,analyses its basic characteristics,the factors influencing the physical mechanism and band gap,and discuss the material properties and distribution for the band gap structure characteristic,the influence of the inner lining of the local oscillator equivalent mass,stiffness change decided the first gap starting frequency,outer equivalent mass,stiffness of the local oscillator change decided the third band gap cut-off frequency,by adjusting the equivalent mass than the different band gaps can be merged into a broadband.Secondly,based on the low-frequency composite resonance mechanism,the crystal structure of composite resonance phonon is improved and the band gap frequency is adjusted.At the same time introducing fractal geometry used in phononic crystal cell structure design,design of porous phononic crystal,calculate different pass yuan cell combination of phononic crystal band structure,geometry size,rotation Angle for the band gap change rule and the influence of such factors as open the physical mechanism behind the band gap,it is concluded that the ability to open in the band gap,the phonon crystal cell in the round hole is better than that of square hole,for the square hole,the maximum level of 45 ° open hole rotating band gap.Finally,the sound absorption characteristics of phonon crystals are analyzed,and the influence of the geometry size,material properties and backing size of phonon crystals on the sound absorption coefficient of phonon crystals is studied.Several sets of local resonant phonon crystal samples and composite multiple resonant phonon crystal samples with different cell shapes and sizes were prepared for sound absorption test.The results obtained were close to the simulation data.Finally,the error of the results was analyzed.