An electromechanical impedance approach for quantitative damage detection inTimoshenko beams with piezoelectric patches

Abstract

As a qualitative health monitoring method, the electromechanical impedance technique(EMI) has been widely studied. Due to the complexities of the damaged structures and thedifficulties in high-frequency analysis, further information about the nature of damagecannot be obtained using EMI in its conventional non-model-based way. Thus, in thispaper, a hybrid technology combining the EMI technique and reverberation matrixmethod (RMM) is proposed to quantitatively correlate damage in beam structureswith high-frequency signatures for structural health monitoring. Timoshenkobeam theory is employed to study the dynamics of beam-like structures bondedwith multiple pairs of PZT patches. A piecewise, homogeneous beam model isintroduced to approximate the nonhomogeneous beam in which inhomogeneity isintroduced because damages of an originally uniform beam can be modeled by differentcross-sectional properties. Here, only one-dimensional axial vibration of PZTwafers is considered. A shear lag model is adopted to simulate the interfacialbonding between PZT patches and the host beam. An analytical expression ofimpedance (or admittance) related to the response of the coupled model of thePZT patch-bonding layer–host beam system is derived and then investigated bycomparing with other theories. Finally, covariance, a kind of non-parametric damageindex, is also employed to identify the damage severity, propagation and location.