Effect of external vibration on PZT impedance signature of plate structure

Electromechanical impedance (EMI) technique using lead zirconate titanate (PZT) transducers has been increasingly applied to structural health monitoring (SHM) of aerospace, civil and mechanical structures. The PZT transducers are usually surface bonded to or embedded in a structure and subjected to actuation so as to interrogate the structure at the desired frequency range. The interrogation results in the electromechanical admittance (inverse of EMI) signatures which can be used to estimate the structural health or integrity according to the changes of the signatures. In the existing EMI method, the vibration of the structure caused by the external excitations has been considered only for one dimensional scenario. This paper develops a two dimensional EMI model to account for the effect of external excitation on the PZT admittance signature. An application is illustrated with modeling of a simply supported Kirchoff plate interrogated by a single surface-bonded PZT transducer. Numerical simulation is also carried out to verify the theoretical model. Finally, the effect of external excitation on PZT impedance signature is discussed.