Research On Propagation Of Acoustic Waves In Phononic Crystals With Magnetorheological Fluids

Phononic crystals(PCs)are a kind of composite material with periodic array structure.Owing to the periodic structure,PCs are endowed with peculiar properties that elastic wave in certain frequency range which is called the band gap is forbidden when elastic wave propagates through the PCs.In general,the band gap is determined when the composition and structure of the PCs are defined.In the face of the complex engineering application environment,the determination of band gaps of the PCs has not been able to meet the practical needs of the project,so it is necessary for us to have an investigation of phononic crystals with tunable band gap.Magnetorheological fluid(MRF)is a kind of intelligent material with controllable properties,which is considered to be one of the most promising materials.It is reversible that when there is no external magnetic field,the magnetorheological fluid exists in the liquid state and after the magnetic field is applied,the magnetorheological fluid rapidly becomes a solid state.This phenomenon reflected in the material parameters is the change of the viscosity and viscosity of MRF.Based on the above discussion,we present a kind of PCs with MRFs and its band gaps can be tuned by the magnetic field for the reason that modulus of MRFs can be changed by means of the magnetic field in this paper.In order to obtain the band gap of PCs under different magnetic fields,firstly shear storage modulus and loss modulus of the MRF with the magnetic field are measured by experiment.Secondly,Perfect periodic and defect PC model with MRF are designed and then measured using LMS.The transmission of vibration under different magnetic fields is also achieved.At the same time,the band gaps of the model are calculated with the COMSOL simulation software.At last,we compare the band gaps measured by experiment and calculated by the finite element method.The cause of the error is analyzed and the influence of magnetic field on the band gap is summarized also.Main conclusions include: the shear storage modulus and loss modulus of MRF increase with the increase of magnetic flux density until the magnetorheological fluid reaches the magnetic saturation state;with the increase of the flux density,the location and width of the band gap of the one-dimensional phononic crystal and the two-dimensional phononic crystal plate with MRFbecomes larger;compared with the aluminum / water phononic crystal with perfect periodic structure,the one-dimensional phononic crystal beam with magnetorheological fluid as a defect appears the phenomenon of hindering the propagation of wave in phononic crystals with the increase of the number of periodic defects;with the increase of the flux density,the location and width of the band gap of the phononic crystal beam with three periodic defects with MRF becomes larger,this law is in good agreement with the rule of the band gap of the perfect periodic phononic crystal with perfect period tuned by MRF.