Characteristic Study Of Bandgaps In One Dimensional Solid And Liquid Phononic Crystals

Phononic crystal is a new type composite materials with elastic wave band gaps properties. When the elastic wave propagation in the phononic crystal, some frequency range of the elastic wave will be suppressed, form the phononic band gaps. Band gap of phononic crystal characteristics can realize effective control of elastic wave, make it in the inhibition of acoustic radiation, weak coupling design, acoustic filter and acoustic functional devices will have broad prospect of application. The phononic crystals bandgap reference to the complex acoustic characteristics in the design of the plate and shell structure, it will not only satisfy the board class structure is widely used in engineering, and solve the problem of the structural vibration and acoustic radiation, has become a new research hotspot recent years, in engineering field.As new composite functional material have sprung up, some solid can only transfer P wave, is regarded as a generalized liquid medium, such as polyethylene, quartz, etc. with the solid immersion liquid solid-liquid phononic crystal, compared to this kind of solid-liquid medium phononic crystal conditions are usually solid, and can be separated from liquid medium environment.First of all, the transfer matrix method is used to calculate the transmission characteristics of one-dimensional solid-liquid phononic crystal. Die at the edge of the transmission spectrum of the forbidden band, belt, the change of the transmission parameters such as peak, analyzes the model of materials, orderliness, incident Angle and other conditions on the impact of transmission. Study found: when synthetic materials acoustic impedance is large, periodic and quasi-periodic phononic crystals are forbidden band, and accompany with edge resonance, but with the loss of the short-range order, quasi-periodic structure of the bandwidth in periodic structure, band edge resonance enhancement, appeared in the forbidden band transmission peak; when Synthetic materials of acoustic impedance approaches, there is no clear forbidden band; With the increase of elastic wave incident Angle,the transmission spectrum to high frequency moving, when the incident Angle is greater than the critical Angle, resonance occur hence wear, transmission peak in the transmission spectrum.Then, by using the finite element software COMSOL Multiphysics are calculated by one dimensional phononic crystal band structure of a plate of solid and liquid. From the aspect ratio of plate, the structure of order and the introduction of defect mode, three aspects, the influence of the dispersion curves are analyzed. The results show that the solid-liquid periodic one dimension phononic crystal plate, with the increase of cycle direction size, the band gap grows wider and move to low frequency, In the other direction of the increase of size, did notchange significantly forbidden band; With the loss of the order than the original cell structure,forbidden band width and move to low frequency, at the same time there is an obvious forbidden band of the low frequency range.Finally, using the finite element software COMSOL Multiphysics are calculated by one dimensional solid liquid phononic crystal sheet of sound transmission loss. According to the transmission spectrum of the before and compares them with the band structure of the similarities and differences of sound transmission loss, found the transfer matrix method and finite element method, they calculated the conclusion completely consistent. Then, made up of granite and polyethylene is one dimension phononic crystal sheet for the model of solid and liquid, analyzes the model of the structure of the order influence on the sound transmission loss. The result show thin plate model with the reduction of structure order of sound transmission loss of loss interval narrowing, loss decreases, but the losses are interval number increased and move to low frequency; Then, through the equivalent replacement steel, resin,quartz and other defects are introduced to study the effect on the sound transmission loss,found that the introduction of the defect scatterer and changed the model matrix of impedance ratio and equivalent elastic constants, so as to change the cyclical and acoustic model of the coupling.