Research On The Properties Of Elastic Wave Control Based On Acoustic Topological Insulators

Vibration in engineering equipment seriously affects equipment performance,service life and personnel safety.Low vibration has become an important index of engineering equipment performance and therefore the research on vibration control has received wide attention.The essence of vibration control is the control of elastic wave propagation and dissipation in the structure or medium.The “control” of elastic waves is twofold: guidance and absorption,and this paper focuses on the first aspect.The traditional elastic wave guide methods are based on defect states and directional propagation properties of phononic crystals.However,as engineering conditions become increasingly complex,the wave propagation characteristics of phononic crystal gradually show their limitations.The main drawback is the strong back scattering effect due to geometric boundaries and defects.By considering the analogue of topology insulator theories in quantum and electromagnetic fields,the concept of acoustic topology insulators was proposed in 2015,which can have defect-insensitive propagation characteristics.This potentially can break through the limitation of traditional elastic wave guiding methods,and provide a new way for vibration control in the structures.The main research contents are summarized as follows:1.The design of acoustic topological insulators is based on the band characteristics and topological properties of the periodic structures.Firstly,the basic theory of band characteristics of 1D and 2D elastic periodic structure is analyzed.Based on this,the characterization method of topological properties of the bulk band is introduced.This method has laid the theoretical foundation for the design of the acoustic topological insulators.2.The method of constructing topological insulators based on the band inversion mechanism is studied.The study has found that,as the parameters of period cell vary,the band gap has disappeared and reappeared showing a transition of topological phases.Based on it,by constructing a finite structure consisting of two periodic structures with different topological phases,a boundary mode at the topological interface is shown.Based on this mechanism,the 1D and 2D topological insulators are designed and the topological boundary states are realized.3.In this paper,the preparation of experimental samples and experimental verification of 2D topological insulators are studied,based on the design principle of the topological insulators.The characteristics of accurate control and directional guidance are verified.In summary,this paper focus on the studies the elastic waves control characteristics of topological insulators,and the experiment validation is carried out.The work of this thesis paves a foundation to the future work of implementing the concept of topological insulators in vibration control.