Defect States And Vibration Energy Recovery Of Novel Two-dimensional Piezoelectric Phononic Crystal Plate

As a kind of artificial periodic composite material with unique structure,phononic crystal has a variety of characteristics to regulate the propagation of elastic waves,so it has a broad potential application prospect in acoustic waveguides,portable devices and wireless sensors.This dissertation designed a four prisms by parcel organic glass coating piezoelectric materials connected in a square lattice periodicity on four epoxy resin board form a type of 2D phononic crystal piezoelectric plate,using cellular automata method combined with finite element method to calculate the band gap of phononic crystal plate under different electrical boundary conditions of structure and transmission loss.By studying the displacement vector field of phononic crystal plate,the vibration mode of phononic crystal is analyzed.On this basis,the formation mechanism of band gap is analyzed and the geometric structure of phononic crystal is optimized.The vibration energy is recovered by introducing point defect and external rectification circuit.The composite waveguide with tunable path is realized by introducing a wire defect.The main conclusions are obtained as follows:Based on the research of vibration energy recovery of point defect,we designed a four prisms by parcel organic glass coating piezoelectric materials connected in a square lattice periodicity on four epoxy resin board consisting of a 2D phononic crystal piezoelectric plate,and use the super cell method combined with finite element method to calculate the band structure and transmission losses of the perfect phononic crystal plate and phononic crystal plate with defects,respectively.By changing the electric boundary conditions on the upper and lower surfaces of the piezoelectric scatterer,a point defect waveguide is formed to limit the elastic wave energy flow.When the frequency of the defect state appears in the band gap,the response frequency range of the defect state expands accordingly,so the mechanical energy of a wider frequency range can be collected.The vibration energy recovery circuit is used to connect the electrodes at the defects on the upper and lower surface of the piezoelectric sheet and convert the mechanical energy generated by vibration into electrical energy.Based on the research of tunable composite waveguide with line defect,the tunable local resonance waveguide is formed by changing the electric boundary conditions applied on the upper and lower surfaces of the piezoelectric scatterer.This new type of waveguide overcomes the limitation that the direction of the waveguide cannot be changed when the material and structure parameters have been determined.It can realize the tuning of the operating frequency of the waveguide in a large frequency range.In addition,the path of the waveguide can be controlled by changing the spatial distribution of the electrical boundary conditions.The active control of band gap of piezoelectric phononic crystal plate is studied.By introducing point and line defects,the vibration energy recovery and tunable waveguide are realized,and the cladding structure solves the problem that the piezoelectric material is difficult to be embedded into the matrix material.The main conclusions can provide support and reference for the realization of devices such as acoustic transducer and frequency filter,and also provide a reliable basis for the design of phononic crystal structure model for active control transmission,guidance,switching and emission of elastic wave.