Study On Vibration And Noise Reduction Characteristics Of Folded Periodic Structures

Phononic crystals are man-made structures with periodic composites,which can prevent the transmission of elastic waves,known as bandgap characteristics.Due to the bandgap characteristics,phononic crystals have attracted extensive research from scholars both domestically and abroad,and have broad application prospects in the field of vibration and noise reduction.There are two recognized mechanisms for the formation of the band gaps in phononic crystals: Bragg scattering mechanism and local resonance mechanism.Based on the Bragg scattering mechanism,this paper designs the variable cross-section phononic crystal unit cells and proposes a new folded S-type structure.The transmission characteristic curves and sound insulation curves of the structures are studied using finite element simulation software.Vibration response experiments are also conducted to verify the bandgap property of the structure.By changing the arrangement of phononic crystals,reducing the size,retaining and widening the bandgap,and exploring the sound insulation applications of the phononic crystals.The main work of this article is as follows:Firstly,this paper designs a one-dimensional variable cross-section phononic crystal,and analyzes the bandgap characteristics of the phononic crystal using the COMSOL Multiphysics multi-physical field simulation software based on the finite element method.Design the unit cell structure of variable cross-section phononic crystals to broaden their bandgap width and reduce the initial frequency of the bandgap.The frequency domain response curve and sound insulation curve of phononic crystals were calculated using simulation software.Within the bandgap frequency range,phononic crystals have good vibration and noise reduction effects,and the impact of different conditions on sound insulation was analyzed.Exploring the arrangement of phononic crystals based on one-dimensional hole digging and variable cross-section phononic crystals.This article designs an S-type folded phononic crystal structure,which can reduce the size of phononic crystals while retaining their bandgap.On this basis,a folded S-type structure combining multiple cells was designed,which can combine the bandgap of different cells to obtain a wider bandgap.This was verified through simulation and experiments.Analyze the special straight lines appearing in the band diagram of the folded S-type structure combined with multiple cells.The effect of different conditions on sound insulation is also analyzed.Based on the above research,a two-dimensional perforated variable cross-section phononic crystal is designed and combined with the advantages of the S-type folded structure,the two-dimensional phononic crystal was folded to form a phononic crystal sandwich panel.A model is established using finite element simulation software to analyze the transmission characteristics of the folded phononic crystal sandwich panel,and the sound insulation properties are calculated.