Research On MRE Control Propagation Of Acousticwaves In Phononic Crystal

Since the proposing of the concept,phononic crystals(PCs)have become a prominent research topic dueto their uniquephysical properties and many promising applications.One of the special characteristics of PCs is the existence of absolute band gaps(ABGs)that the acoustic wave at a certain frequency range could not propagate.According tothis features,PCs can be diffusely used infiltering and vibration attenuation etc.Magnetorheological elastomer(MRE)is a new generation material made of polymer matrix with micron sized ferromagnetic particles randomly dispersed in it and its physical properties can be changed by the magnetic field.Particularly,the elastic modulus of MRE is increased significantly when subjected to the action of magnetic field.In this paper,the band structures in MRE phononic crystals are studied with the aim to clarify the effect of modulus on the band gap.The main work of this paper is as follows.(1)The suitable matrix,additives and ferromagnetic particles were screened out.Two kinds of magnetorheological elastomers were prepared by the method of pre-structure and non – pre-structure.The results show that the elastomeric properties of the two elastomers are pretty good,and the anisotropic magnetorheological elastomers have the best performance under the 0.8T magnetic field.(2)Acoustic waves in a phononic crystal which consists of MRE and PMMA periodic structure is studied.At the experimental stage,the bandgap of the phononic crystal designed by ourselves is recorded under different magnetic fields measured of Gauss meter.Finite element method is used to analyze the band gap of the acoustic waves in phononic crystal and the results are verified by experiments.The propagation of acoustic waves can be affected by the MRE whose storage modulus influenced by the magnetic field,which means,the band gap can be tuned by changing the magnetic field intensity.(3)A kind of local resonant artificial periodic beam structure is studied.On one hand,the magnetic field is changed in the experiment to measure its dispersion curve.On the other hand,the finite element Comsol software is used to calculate the vibration mode and the bandgap.The results show that the magnetic field has an influence on the band gap of the beam structure.