Design And Simulation Of Anti-Symmetrical Trapezoidal Cantilever Plate Peh With Mass Frame

Piezoelectric material can convert mechanical energy into electrical energy by the piezoelectric effect.The piezoelectric energy harvester(PEH)made of this material has the characteristics of simple structure and high conversion rate,which has attracted widespread attention of scholars.However,because of the narrow working frequency band and low output voltage of the traditional cantilever structure with tip mass,scholars began to study a new structure to make the PEH have more working frequency bands and higher output voltage on the basis of compact structure,so as to improve the energy conversion efficiency.With the widespread use of micro-electronic components,because of PEH can be self-powered,miniaturization is a research trend.However,classical continuum mechanics theory cannot accurately describe the mechanical behavior of the structure in micro-size,so how to simulate the micro PEH is also an urgent problem to be solved.In this paper,a new type of PEH surrounded mass frame is designed.The vibration characteristics and energy capture efficiency of the structure are calculated by using ABAQUS finite element analysis software.A prototype of the structure is designed for experimental verification and parameter study.By introducing strain gradient theory and using ABAQUS UEL to customize a micro-piezoelectric element,a finite element program for modal and dynamic analysis of micro-structures is developed,which can be used to analyze the natural frequency and output voltage of PEH under micro-size.The main research contents are as follows.(1)A kind of PEH with double cantilever plate surrounded mass frame is proposed.According to the distribution of two plates and the shape of its,three structural forms are proposed.By using ABAQUS finite element software,the natural frequencies and output voltages of three kinds of structures and traditional single cantilever plate with tip mass structure and other literature structures are compared,and the optimal structure is determined to be composed of two anti-symmetrically placed variable cross-section trapezoidal cantilever plates surrounded mass frame.The influence of the laying area of piezoelectric layer,the ratio of topline and baseline of trapezoidal plate and the geometrical size of frame on the energy conversion effect is also studied.(2)Based on the optimal structure determined by finite element analysis,a prototype of the PEH is made and tested.The prototype is connected with the exciter by custom fixture,and the signal generator is used to simulate the external vibration.Eight groups of comparative tests were designed to study the influence of the thickness of trapezoidal plate and the weight and size of mass frame on the natural frequency and output voltage of the structure.The relationship between the output voltage and the frequency of external excitation is plotted.Based on this experiment,the optimal structure is determined.(3)Based on the combination of ABAQUS user-defined element subroutine(UEL)and strain gradient theory,a piezoelectric element for microstructural simulation is designed.Using the strain gradient theory,a new constitutive relation is designed to solve the scale effect of microstructures.At the same time,the computational program of the new element for modal,static and dynamic conditions is compiled.Then compared with the ABAQUS self-contained element,which verifies the necessity and accuracy of the proposed micro-element.(4)In this paper,the AFT PEH is miniaturized,and its vibration and energy capture characteristics are studied by using the developed micro-piezoelectric element.The natural frequencies,mode shapes and output voltages of AFT PEH at micro-scale are studied by using the finite element program for modal analysis and dynamic analysis of micro-structures compiled in this paper.By studying the influence of the geometrical size of the frame on the energy conversion effect,the appropriate structural parameters are determined.