Model Design And Experimental Study Of Solid/Solid Bragg Phononic Crystals

Phononic crystal(PC)is a kind of artificial composite structure composed of different elastic properties of materials periodically.The most important property of PC is its band gap characteristics.During the process of elastic waves going through the PC,the elastic waves which frequency is in the range of band gap are forbidden in the propogation due to the interaction with periodic structure of PC.While other elastic waves in different frequencies own the ability to propogate without loss.With the specialty of frequency-designed of band gap,PC has a broad application prospect in the field of vibration and noise reduction.In this paper,the law of band gap of solid / solid phononic crystal with perduren/rubber as its one-dimensional matrix was explored in simulation.Based on the finite element method,this research used multi physics simulation software COMSOL to make simulation analysis on the above materials and explored the effect of different material density ratio,filling rate,and the lattice constant on the band gap of one-dimensional solid /solid PC.The simulation results showed that in the one-dimensional two component tetragonal PC with cube as its scatterer case,by increasing the density ratio of scatterer to matrix and the lattice constant are beneficial to reduce the initial frequency of the first vibration band gap.At the same time the increment of density ratio of scatterer to matrixand filling rate,while reducing the lattice constant,the width of band gap will increase.As the filling rate increasing,it is expected to open a number of bandgap.Then,by means of COMSOL,the research on the law of band gap of solid / solid PC with perduren/rubber as its two-dimensional(2-D)matrix was aslo explored in simulation.To be specific,the analysis on scatterer being as cylinder and cube respectively of the PC were carried out and the effect of density ratio of scatterer to matrix,filling rate and lattice constant on the band gap of 2-D PC were investigated thoroughly.The simulation results showed that in the two-dimensional two component tetragonal PC with cube as its scatterer case,by increasing the density ratio of scatterer to matrix and filling rate while reducing the lattice constant,the width of band gap will increase.At the same time the increment of density ratio of scatterer to matrix,decrease of filling rate and the lattice constant are beneficial to reduce the initial frequency of the first vibration band gap.In the two-dimensional two component square lattice PC with scatterers as cylinders,the increase of the density ratio of the scatterers to matrix and the decrease of lattice constant are favorable for increasing the band gap width.Based on the study of two-dimensional solid / solid phononic crystals,the experimental investigation of two-dimensional phononic crystals is carried out.The experiments are divided into two parts: Firstly we designed a series of two-dimensional phononic crystal with silicone rubber as matrix and chose air and 45 steel as the scatterers respectively,then made simulations on these materials.Then the advanced machining technology was used to process the phononic crystal.The test results were compared with the simulation to verify the experimental results.On the basis of the first experimental test,we adjusted the model structure of phononic crystal,designed cross shaped solid / hollow cylinder phononic crystal and made simulations in comparison with the experiments.The experimental results illustrated that when compared with the traditional cylindrical PC with the same size,cross solid cylindrical PC and cross hollow cylindrical PC could significantly extend and reduce the first band gap range,and effectively reduce the overall quality of PC structure.The band gap characteristic of phononic crystal manage to reduce vibration and noise effectively thus this kind of materials have a high potential to be widely applied in aerospace,precision machinery,military weapons and other fields in the future.