Analytical Model of the Electro-Mechanical Impedance Response of Frame Structures with L-Shaped Beams

The electro-mechanical impedance (EMI) method has been accepted as an effective technique for detecting damages in the Structural health monitoring (SHM). EMI at any point of the structure depends on material properties, geometry and boundary conditions that all appears in dynamic stiffness of the structure. In spite of the expensive experimental methods for measuring the mechanical impedance, or the cheaper one electromechanical impedance, of structures, various analytical methods could be substitutions for them. In this paper, an analytical method is developed to obtain the EMI response of L-shaped beams through calculating the dynamic stiffness of the structure. To verify the model, an experimental setup with an embedded piezoelectric wafer active sensor (PWAS) is carried out. The results have shown that EMI and its real part, extracted by the current analytical method, are with good agreement of the experimental results. Also, the dynamic stiffness of the structure directly depends on the mode shapes of the structure and its natural frequencies in terms of the excitation frequency. The peaks of the real part of the EMI results related to the coincidence between agitation frequency value and natural frequencies of the structure.