Damage severity and propagation characterization with admittance signatures of piezo transducers

The electromechanical (EM) impedance method is emerging as an effective tool for structural damage detection. Damage is detected by changes in the EM impedance signatures of the smart piezoelectric transducer bonded on the structure. The damage quantification has so far been restricted to using non-parametric statistical indices to measure changes in the signatures. Such measures, although simplistic, fail to correlate the changes in the signatures to physical parameters of the structures. Thus, although effective in detecting the presence of damage, the method fails to give further information about the location and severity of the damage. In this paper, the EM impedance method integrated with a finite element (FE) model is presented as a means for characterizing damage growth. Damage growth is characterized by quantifying the changes in the natural frequency shifts of the structure extracted from the EM admittance signatures. A new damage characterization index is derived, which is experimentally validated to be capable of distinguishing a localized increase in severity from damage propagation through the structure.