Research On Damage Identification Of Piezoelectric Smart Structures

Electro-mechanical impedance (EMI) method is applied to structural health monitoring. It has attracted wide attention in recent years. The basic principle is that the damage of structure could change its mechanical impedance. Electromechanical coupling effects of piezoelectric material could be used as structure mechanical impedance, but it is difficult to be tested directly. So the impedance technique measures the electrical impedance across the piezoelectric transducer attached on or embedded in a target structure, and it can be shown that the electrical impedance of the PZT is coupled with the mechanical impedance of the main structure. This technology is sensitive to minor structure damage on the early stage because of the high frequency scope of working frequency in the alternating electric field. This paper has researched the damage identification of the most common structure damage in civil engineering by piezoelectric impedance technology, which is sensitive to the tiny crack. In this paper, the main research work include:1、The effect of temperature on the impedance of PZT piezoelectric was analyzed by the finite method, because of the piezoelectric patches is sensitive to the temperature in piezoelectric impedance technology. The admittance spectrum in different temperature of piezoelectric patches was obtained. The conclusion shows that the resonance peak value of piezoelectric patches will be increased with the increase of temperature.2、The coupling system between piezoelectric patches-bonding layer-subject was established, aiming at the beam structure. And the universal finite element software ANSYS was used through the analysis method of three-dimensional finite element harmonic response. By this way, the coupling system was simulated and the feasibility of the piezoelectric impedance method is proved. The influence of the parameters of the bonding layer (thickness of bonding layer, elastic modulus, poisson ratio, etc.) and piezoelectric excitation voltage on the piezoelectric admittance was analyzed by the finite method. Moreover, the damage of plate was researched based on the piezoelectric impedance technology. The conclusion shows that the effectiveness of piezoelectric impedance technology applied to the plate structures are proved.3、The piezoelectric impedance method is applied to the bolt looseness, and the electrical admittance curves in different pretension force was simulated. Also, the degree of damage can be identified through the damage index RMSD.The Above research work demonstrated that piezoelectric impedance technology could be used for damage identification of engineering structure.