Piezoelectric Sensor Technology In Structural Health Monitoring Study

With the rapid development of modern technology and the rising safety awareness of people, structural health monitoring and damage detection have attracted wide attention in recent years, the study on real-time and on-line structural health monitoring has become one of the most active research fields in civil engineering as well. Structure health monitoring is a new technology base on multidisciplinary integration and has acquired a novel method on account of the development of intelligent materials. Piezoelectric materials, with functions of both sensing and actuating, have become one of the most widely used intelligent materials in structural health monitoring, owing to its distinct advantages, such as quick response, broadband frequency and low price. Supported by the National Natural Science Foundation of China (No.50778179), piezoelectric sensing technology in structure health monitoring has been studied. In this thesis, the main research works and results are as follows:Firstly, the calculating formulation and the sensibility expression for piezoelectric ceramic sensor are deduced based on piezoelectric sensing principles and the difference between voltage amplifier and charge amplifier is compared on the point of signal extraction, demonstrating that the charge amplifier has the advantage of being not affected by wire cable.Secondly, according to the piezoelectric sensor in thickness-shear mode, the strain-transfer relationship between the host structure and the piezoelectric sensor is obtained, the numerical results of which illustrate that the thin and soft piezoelectric patch is supposed to be chosen so that the better output of electric signal can be easily acquired. Meanwhile, the output response of the sensor changes along with the damage factor:the higher damage degree, the lower sensor sensibility.Finally, based on the electromechanical coupling theory, the interaction between the electric impedance of piezoelectric element and the mechanical impedance of host structure is deduced so that the piezoelectric sensor/actuator integration technology for structure health monitoring is obtained. The finite element method (FEM) and the applications FEM software ANSYS in piezoelectric analysis are introduced. The modal frequency affected by structural crack is studied and the piezoelectric frequency-admittance spectrum under resonant voltage excitation is analyzed. The results show that piezoelectric impedance analysis using FEM is able to distinguish the tiny defection of the structure and to estimate the elementary expansion of the crack.