Design And Research Of Elastic Topological Metamaterials And Deformed Phononic Crystals

Phononic crystals have become an important tool for studying the propagation properties of acoustic waves in periodic artificial material in recent decades.With this theory,one can design composite materials with extraordinary acoustic characteristics to meet demands from military and industrial fields.At the same time,phononic crystals have the potential to subvert traditional materials in the fields of vibration and noise control.In this paper,some research work has been carried out on two popular directions of phononic crystals: the acoustic metamaterial and the tunable phononic crystal.The main contents are as follows.1.In this paper,by exploring the characteristics of the band structure of twodimensional phononic crystal,a new acoustic topological metamaterial with out-ofplane resonators is designed.The simulation results indicate that this metamaterial can realize both the valley spin Hall effect and the quantum spin Hall effect,and two acoustic topological effects are verified by significant topological phenomena such as single-boundary transmission of sandwich structure and zigzag boundary transmission.A simple analytic model is proposed for the structure to qualitatively describe the original structure,and the valley vortex states can be successfully derived.The valley spin Hall effect is also demonstrated in this paper by experiments.2.In this paper,the anti-tetrachiral honeycomb material with negative Poisson’s ratio is also studied in depth.Firstly,the structure is simplified by symmetry,and its theoretical model of large deformation is given.Then the property of negative Poisson’s ratio of the structure is predicted.The simulation results are in good agreement with the theoretical predictions,and can give a specific source of theoretical error.Next,the acoustic performance of the structure undergoing large deformation is explored,and the qualitative description of the influence on its acoustic performance is given.Based on this,an elastic analogue of the electrical switch is designed which can realize the normally open and normally closed switch,providing ideas for the design of acoustic switches controlled by large deformation.