Study On Vibration Isolation And Noise Reduction And Topological Interface State Of Quasi-periodic Phononic Crystal Plates

Phononic crystals play the role of vibration and noise reduction in automobile,machinery and industrial production,and have been favored by experts and scholars at home and abroad,due to the unique gap bands,which can suppress the propagation of sound waves.Especially in recent years,researchers have introduced topolog y into phononic crystals,which not only expands the research scope of phononic crystals,but also broadens its application.Most of the previous studies were based on periodic structures,and it is generally difficult to obtain accurate,rigorous periodic phononic crystals due to defects in the material and errors in the manufacturing process.Quasi-periodic phononic crystals are more advantageous than periodic phononic crystals in terms of robustness,band gaps properties and topological interface states.Therefore,it is more of significance in studying of band gaps and topological interface states of quasi-periodic phononic crystals.In this paper,based on the basic theory of elastic wave dyn amics and the eigenmode matching theory,the band gaps of quasi-periodic phononic crystal plates are studied.The effects of these parameters on the band gaps have been studied and analyzed by adjusting the material and structural parameters of the quasi-periodic phononic crystal plate.Secondly,the topological interface states of quasi-periodic phononic crystal plates have been studied by acoustic impedance theory,and the influence of structural parameters on topological interface states have been analy zed.The main work is shown as follows:(1)Using eigen-mode matching theory on MATLAB and the finite element simulation software COMSOL Multiphysic to calculate the transmission spectrum of Fibonacci sequence phononic crystal plates.It has been found tha t the numerical calculation results and the results of finite element simulation are highly consistent,which indicate the research methods are correctness.(2)The effects of materials on their band gaps width and position have been studied and analyzed on Fibonacci sequence and periodic phononic crystal plate structures.(3)On the Fibonacci sequence phononic crystal plate structures,the influence of structural parameters(occupancy ratio,plate thickness,quasi-periodic algebra)on the band gaps width and position have been studied.(4)On the Fibonacci sequence phononic crystal plate structures,the existence condition of the topological interface state has been studied.The influence of occupancy ratio and quasi-periodic algebra on the topological interface state has been also explored by using this condition.In summary,the propagation characteristics of horizontal guided waves in quasi-periodic phononic crystal plates has been studied.The effects of material and structural parameters on the band gap have been discussed.The existence condition of topological interface states in Fibonacci phononic crystal plates has been also studied.The influence of structural parameters on its topological interface state has been explored.These studies have laid an important theoretical foundation for the application of quasi-periodic phononic crystal plates in vibration and noise reduction and information transmission,as well as the research and development of new acoustic instruments.