Research On Sound Insulation And Noise Reduction Based On Magnetoelastic Phononic Crystal Slabs

The development of modern industrial civilization is always accompanied by harmful vibration and noise.How to deal with it is a serious problem that we are facing.One of the common methods is using special material to attenuate vibration and noise in the path of propagation.As an artificial periodic composite material,phononic crystal slab which have the band gap character provides a new idea to the research of vibration and noise reduction.At present,based on Bragg scattering theory and local resonance,the periodic structure,which can control the propagation of elastic wave in a certain frequency range,could be designed by modifying the structure of unit,geometric parameters and material composition.However,these design variables are difficult to change in practical use.This problem not only limits the application of phononic crystal slab,but also reduces the flexibility of it greatly in engineering.This paper theoretically investigates the band gaps of Lamb mode waves in the magnetoelastic phononic crystal slabs by an applied external magnetostatic field.With the equivalent piezomagnetic material model,the effects of magnetostatic field on phononic crystals are considered carefully.The numerical results indicate that the band gap is significantly changed by applying the external magnetic field with different amplitude and orientation,and the proposed phononic crystal slabs show obvious contactless tunability by an external magnetostatic field.The main contents are as following:(1)The one-dimensional magnetoelastic phononic crystal slab model is established.Then,the plane wave expansion method and the finite element method which is used to calculate the band structures of the model.(2)Based on the assumption of uniformly oriented magnetization,an equivalent piezomagnetic material model is used.With the full consideration about the demagnetization effect,the influence of applied external magnetostatic field on the magnetostrictive material Terfonel-D is studied,and the effective material parameters is calculated in detail.(3)According to the equivalent material parameters,the band structures of the one-dimensional magnetoelastic phononic crystal slab model was calculated by the plane wave expansion method and the finite element method.The results of two methods show a good agreement.Then,we investigates the band structures with different external magnetic field and plots the band gap maps.The results indicate that antisymmetry mode of Lamb wave is more sensitive to the variation of external field than symmetry mode.The tunability of band gaps is significant by varying the amplitude and the orientation of the external magnetic field.(4)The two-dimensional magnetoelastic phononic crystal slabs model is established,and the tunability of the band gaps of plate waves in this model is studied by varying external magnetic field.The calculations demonstrate that the first band gap is significantly changed by varying the amplitude of external magnetic.Furthermore,the anisotropy of the model can be improved by changing the orientation of magnetic field,and it has significant effects on the tunability of band gaps.