ELECTRO-MECHANICAL IMPEDANCE BASED SHM OF THICK STRUCTURES IN BROAD-BAND FREQUENCY SPECTRUM

Abstract

In this study, theoretical and experimental studies were conducted in terms of electro-mechanical impedance spectroscopy (EMIS) to monitor the structural health status of thick metallic bar structures in broad-band frequency in the range up to 15 MHz. Thus, in-plane (longitudinal-wise) and out-of-plane (thickness-wise) mode EMI spectra were included in this range of frequency. Then, the thickness mode EMIS peaks were focused for pristine thick steel bar as a baseline and for bars with simulated damage in different depths and different locations. For theoretical part of the study, coupled field finite element analyses (CF-FEA) were carried out by modeling piezoelectric wafer active sensor (PWAS) bonded on steel bars in pristine and in damaged status. The thickness mode EMIS results from both CF-FEA simulations and EMIS measurements were analyzed to investigate the effects of the damage location and size variations through a statistical pattern recognition method as damage index such as the root mean square deviation, RMSD, method. It was found that RMSD values were similar trend for experimental and CF-FEA.