Experimental And Numerical Simulation Of Health Monitoring Based On EMI

In recent years, the electro-mechanical impedance (EMI), which utilizes piezoelectric path as sensor, has emerged as a new non-destructive evaluation technique because of its sensitivity to incipient damage, online monitoring and drastic development of computer technique and piezoelectric materials. Its principle is that structural damage could change its impedance, 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 this electrical impedance of the PZT is coupled with the mechanical impedance of the host structure. Therefore, damage in the host structure can be detected by monitoring the change of the measured impedance signal. In this paper, the main research works and results include:(1)To investigate and eliminate the effects of temperature on PZT transducer, admittance signals of piezoelectric patches in different temperature were extracted. The results showed that:the admittance signals shifted upwards and the frequency corresponding to admittance peaks increased as temperature went up. Among10℃-70℃, piezoelectric patch could work well and high temperature could not affected its property. A temperature compensation technique was proposed to minimize the effects of the temperature to admittance signals, and its effectiveness was verified.(2)Crack quantitative development in concrete cubes was investigated. Admittance signals of concrete cubes correspond to healthy condition and several damage conditions was extracted. The results showed that the admittance signals varied with the development of crack in concrete. The peaks of conductance signals and resonance peaks of the coupling system of piezoelectric patches-cohesive course-main structure could indicate the crack development in concrete cubes, but its stability was poor. The effectiveness of Mean Absolute Percentage Deviation (MAPD), Root Mean Square Deviation (RMSD) and Correlation Coefficient Deviation (CCD) in indicating the health condition of host structure were verified.(3)The variation of Crack position in concrete beam was investigated. Admittance signals of concrete beam correspond to healthy condition and several damage conditions was extracted. The results showed that the admittance signals varied with the variation of crack position in concrete beam. The relationship between Correlation Coefficient Deviation (CCD) and crack position was similar linear.(4) Three-dimensional finite element models was proposed to simulate the free piezoelectric patch, concrete cube and concrete beam using software ANSYS. The simulation analytical results were consistent with experimental results, which verified the effectiveness of three-dimensional finite element model...