Research On Band Gap Tuning Methods Of Buckling Acoustic Meta-materials

Vibration and noise not only restrict the development of modern industrial equipment,but also endanger people's physical and mental health.At the same time,low-frequency noise has the characteristics of strong penetration and difficult attenuation,so it is difficult for traditional sound insulation materials to effectively control it.Because of its special band gap characteristics,acoustic meta-materials have a wide range of development prospects in the field of vibration reduction and noise reduction.However,there are some problems in the application of acoustic meta-materials to low-frequency vibration reduction,such as too large structure mass or too narrow band gap,and the band gap range is difficult to adjust.In this paper,the theory and finite element simulation method are used to calculate and analyze the active and passive control of wave propagation in acoustic meta-materials,which has a certain guiding role in the research of low-frequency band gap control method.The wavelength corresponding to the band gap frequency of the local resonance type acoustic meta-materials is much larger than its lattice size,which provides the possibility for the realization of low frequency vibration control of small-scale structures.Because the main determinant of the local resonant band gap frequency is the natural frequency of the unit cell,structural buckling can be used as a way to adjust the band gap.Buckling can greatly change the stiffness of the vibrator,thus changing the natural frequency of the resonance element and determining the frequency range of the band gap.Based on the principle of local resonance,the one-dimensional acoustical meta-material embedded in the beam structure is designed.The generation mechanism and attenuation characteristics of the meta-material band gap are discussed by analyzing the vibration modes,band structure and frequency response of the unit cell.The unit cell band gap is sensitive to the change of geometric parameters,and the influence of the geometric parameters(width,elastic modulus and curvature radius)of the beam on the band gap are discussed.Furthermore,the passive adjustment of band gap of one-dimensional acoustical meta-materials is studied.By applying the prestrain in the beam(i.e.the beam is installed after being bent),it is found that the buckling of the beam can change the equivalent stiffness ratio between the vibrator and the matrix,thus realizing wide range adjustment of the unit cell band gap.The results show that the application of prestrain can effectively adjust the unit cell band gap frequencyof 30%.Compared with the adjustment method of changing parameters,the application of prestrain adjustment has a wider range.By introducing the curved beam structure to connect the matrix and the vibrator,a two-dimensional active tuning acoustic meta-material is designed.And the effects of uniaxial compression and biaxial compression on the band gap of the two-dimensional metamaterial are discussed.The results show that the application of uniaxial compression can reduce the band gap until it is closed,which can be applied to acoustic switch to provide the function of opening and closing the band gap;at the same time,the application of uniaxial compression can reduce the frequency range of the directional band gap,which is conducive to the regulation of the unidirectional propagation of elastic waves.The application of biaxial compression can greatly change the stiffness of the vibrator,reduce the band gap frequency by 53% under the premise of ensuring the bandwidth,and realize the large-scale active tuning of the meta-material band gap.Finally,the extensive applicability of the compression effect of two-dimensional meta-materials under different parameters(number and width of beams)is verified.It is found that the method of controlling the band gap with compression is simple,flexible and effective,which has a certain practical value in the active tuning of low-frequency elastic waves.