The Impedance Model Considering The Shear Lag Effect Of The Bonding Layer On A Dual Piezoelectric Transducer

Piezoelectric smart materials are widely applied in structural health monitoring,due to their high sensitivity to structural small incipient damage.Especially the piezoelectric impedance technology based on piezoelectric ceramics with positive and inverse piezoelectric effects is constantly innovating and developing.Based on a new type of dual piezoelectric transducer,the theoretical derivation,experimental verification and numerical simulation are studied in this thesis.The details are as follows:1.The one-dimensional impedance model of the dual piezoelectric as the outer ring part and the inner part act as the excitation respectively is derived in the polar coordinate system,and a free vibration experiment of the dual PZT patch is conducted to validate the validity of the derived impedance model.Secondly,the commercial finite element software ANSYS is used to model the dual PZT patch and a method to extract admittance signal numerically is proposed which has been verified to be effective by comparing with the results of free vibration experiment.Finally,a numerical model of a simply supported aluminum beam before and after damage is constructed by using ANSYS.The outer and inner parts of the dual PZT piezoelectric patch are taken as the excitation,respectively,and the influence of different excitation parts of the dual PZT patch on the damage identification is studied.2.A one-dimensional impedance model of the dual PZT patch is derived in the Cartesian coordinates,and based on the concept of effective mechanical impedance of the traditional PZT patch,the two-dimensional effective mechanical impedance of the dual PZT is defined.Then the two-dimensional impedance model of the dual PZT in Cartesian coordinates is derived,which has been validated by the free vibration experiment.3.The one-dimensional and two-dimensional impedance models of the dual PZT considering the shear lag effect of the adhesive layer are derived,which have been verified by attaching the PZT patch on the aluminum beam with different bonding layer thickness.Then,the finite element software ANSYS is used to construct a simple supported aluminum beam model with the consideration of the bonding layer,and the correctness of the numerical model is verified by the experimental results.Finally,the influence of the bonding layer thickness,shear modulus,debonding damage on the admittance signals has been studied numerically.The study shows that with the increasing thickness of the adhesive layer or with the decrease of the shear modulus,the amplitude of admittance signal decreases and peak position remains unchanged;while the debonding area is small,with the increase of debonding area,the amplitude of admittance signal decreased and the peak position remains unchanged,when the debonding area becomes large,the admittance cannot reflect the structural characteristics anymore and tends to character the dual PZT itself.