Finite Element Modeling and Effect of Electrical/Mechanical Parameters on Electromechanical Impedance Damage Detection

Electromechanical Impedance (EMI) is a popular SHM technique, which has found applications in many fields of engineering: mechanical, aerospace, civil and others. Active elements of the technique are piezoelectric wafer active sensors bonded or embedded into a structural element. EMI detection of structural damage is achieved by comparing high frequency structural dynamic signatures reflected in the electromechanical impedance measured at the sensor terminals. Over a past decade, substantial efforts have been devoted to analytical and numerical modeling of various aspects of EMI method. The majority of prior studies focused on fundamental understanding of the sensor transduction mechanism and sensor-structure interaction. Although basic principles of the EMI method are now well understood, modeling of practical structural diagnostic scenarios remains challenging. This contribution expands current modeling efforts in the EMI SHM by considering issues related to energy dissipation in piezoelectric sensor and host structure, as well as its effect on detectability of structural damage. Piezoelectric element and a host structure were modeled using Comsol^® Multiphysics finite element package. The finite element implementation allowed for considering contributions of active material, adhesive bond and structural damage. These contributions were studied parametrically for various model settings including mechanical and electrical losses. The study shows that sensor position may directly control damage manifestation in EMI signature; effect of adhesive bond thickness is comparable in magnitude to the effect of bond stiffness; influence of piezoelectric mechanical losses on the impedance signature is different for damaged and undamaged cases.