*WINNER* Finite element simulation of high frequency electromechanical impedance measurements for structural health monitoring
Structural health monitoring (SHM) techniques have been widely used to detect changes in the state of structures to avoid sudden failure in engineering systems. Electromechanical impedance (EMI)-based techniques have shown promising potential in SHM applications due to active sensing capabilities, which can provide engineers with the ability to detect incidence and existence of flaws, track the propagation of damage, and measure the dimension and location of defects. The EMI technique utilizes piezoelectric transducers as the active element to perform simultaneous actuation/sensing on the host structure. While the EMI method presents its best performance in kHz frequencies, the application is limited in MHz frequencies. In this study, using a combined experimental and simulation approach, the sensitivity of an example structure to high frequency, MHz EMI measurements are evaluated. Initially, a test setup including a piezoelectric ceramic bonded on an aluminum cantilever beam is prepared and the impedance is measured using an HP 4194 impedance analyzer. Adding damage to the structure, the impedance measurements are repeated and results are compared to the healthy condition. In addition, a finite element (FE) model is created to obtain a better understanding of the measurements and the effective parameters on the impedance of the piezoelectric element. The FE model is first tuned by characterizing the piezoelectric material properties using an FE-based optimization process. The final model is compared to the experimental measurement and the findings are discussed in order to develop strategies to extend the application of EMI-based SHM using piezoelectric transducers to MHz frequency ranges.