Study On Bandgap Tunability And Vibration Energy Harvesting Of Locally Resonant Piezoelectric Phononic Crystal Plates

One of the most challenging issues today is effectively controlling low-frequency vibration and noise.In daily life,the majority of vibration sources are distributed in the low-frequency range of 50-250 Hz,and the vibration propagates in all directions,with much of the energy transmitted in the form of elastic waves.The prominent characteristics of this vibration and resulting noise are its strong penetrative power,slow attenuation,and similarity to the inherent vibration frequency of human organs,which can cause resonance and harm to the human body.Therefore,effectively controlling low-frequency vibration and noise has become a crucial problem to be solved.However,in practical environments,similar vibrations and resonances exist,which are accompanied by energy loss.If this energy can be effectively controlled and recovered,it can achieve energy conservation and environmental protection for sustainable development.Therefore,using piezoelectric materials to collect vibration energy and utilizing a piezoelectric energy recovery system to regulate elastic waves and improve the conversion efficiency of vibration energy is a key issue for achieving sustainable development.This has significant theoretical and practical value as a reference for both theory and application.This thesis focuses on the tunability of low-frequency band gaps in locally resonant phononic crystal plates and the optimization of bandgaps in locally resonant piezoelectric phononic crystal plates,as well as the response characteristics of the elastic-mechanicalelectrical multi-physical field coupling system.Finite element theory is used to study the factors affecting the band gaps of locally resonant phononic crystal plates in the frequency range of 0-3000 Hz.After introducing piezoelectric materials,a locally resonant piezoelectric phononic crystal plate structure is established,and the elastic wave propagation model of the locally resonant piezoelectric phononic crystal plate is combined with piezoelectric energy recovery theory.The mechanism of band gap formation and vibration energy localization is analyzed,and the voltage amplitude-frequency response characteristics are studied when a single external load or an external circuit is applied.Finally,based on the locally resonant piezoelectric phononic crystal plate,the tunability of the acoustic waveguide structure and the voltage amplitude-frequency response characteristics of the piezoelectric acoustic waveguide mode are studied.The main research content is as follows:A new type of locally resonant phononic crystal plate is proposed,which consists of double cladding layers,scatterers,and a base plate with chamfers.The band structure and displacement vector field of the locally resonant phononic crystal plate,as well as the transmission loss spectrum of a 1×5 perfect supercell,are calculated using the finite element method.The research results show that the relative bandwidth of the locally resonant phononic crystal plate is up to 162.10% in the frequency range of 0-3000 Hz.Compared with the square cylinderbased phononic crystal,the first complete band gap frequency of the hexagonal cylinder-based phononic crystal is lower and the second band gap frequency range is wider.The mechanism of low-frequency band gap formation of this structure based on local resonance is analyzed,and an equivalent model is established.By optimizing the geometric structure,changing the material parameters,and introducing piezoelectric effects,the control of multiple complete band gaps is achieved,and the formation of the complete band gap is further expanded to an ultra-wide band gap.The research results of this article can provide a theoretical reference for the development of adjustable low-frequency vibration reduction and noise reduction products.A locally resonant piezoelectric phononic crystal plate structure was designed to recover wideband low-frequency vibration energy.The band structure and transmission loss spectrum of the piezoelectric phononic crystal plate were calculated using the finite element method.The mechanism of bandgap formation in the locally resonant piezoelectric phononic crystal plate was analyzed,and the effect of introducing defects on the band structure and energy localization was studied.Based on this,a coupled elastic-mechanical-electrical model of the entire system for recovering vibration energy was established.The effects of a single external inductance,resistance,and capacitance load,as well as external circuits,on the vibration frequency response and voltage amplitude frequency response of the locally resonant piezoelectric phononic crystal plate were studied.The results showed that increasing the inductance and resistance values and decreasing the capacitance value can improve the energy conversion efficiency of the system when a single external load is applied.When an inductance is present in the external circuit,a resonant frequency is generated at low frequencies,which is more conducive to the energy recovery of low-frequency vibration noise.These results provide theoretical reference value for experimental testing.To further explore the stability of piezoelectric energy harvesting systems in real life,a tunable acoustic waveguide structure based on the locally resonant piezoelectric phononic crystal plate was designed.Four different paths of line defect waveguide structures were constructed to study the control of geometric structures and material parameters on the waveguide path.The effect of the piezoelectric waveguide on energy recovery under online defect conditions was also considered.The results showed that by constructing different line defect waveguide paths to control the propagation of elastic waves,sound waves can propagate along a specified path at a specific frequency and can also simultaneously propagate in different types of defects at the same frequency,enabling real-time control of the waveguide path.Under the condition of an online defect waveguide,the voltage output of a single load circuit with different resistance values is different,and the maximum output voltage is 1.35 m V when the resistance is 1 GΩ.