Electro-Mechanical Impedance Spectroscopy Leveraging Zero Group Velocity Modes for Structural Sensing

Abstract

This paper presents an Electro-Mechanical Impedance Spectroscopy (EMIS) leveraging zero group velocity (ZGV) modes for active structural sensing. EMIS employs a piezoelectric wafer active sensor (PWAS) as both the actuator and the receiver to achieve structural damage evaluation via structural resonances. Distinctive from the conventional EMIS methodology, this research exploits the ZGV modes originated from localized resonance in thickness direction. The ZGV modes possess the unique property of an elapsed group velocity with a finite nonzero wavenumber and can confine the wave energy within the vicinity of the excitation source. To develop an insight into the mechanism behind the ZGV modes, semianalytical finite element (SAFE) method is implemented to extract and identify the ZGV frequencies and wave modes. Parametric case studies are performed to examine the influence of geometric and material properties change. Subsequently, fully discretized finite element (FDFE) model considering the PWAS is established to conduct coupled-filed harmonic analysis. The obtained EMI spectra verify the capability of PWAS for exciting and identifying the ZGV modes. Ultimately, the experimental validations on aluminum plates bonded with PWAS transducers are carried out to demonstrate the practical feasibility to extract the ZGV modes. The ZGV frequencies are mutually verified in comparison with the SAFE and FDFE results and are in consistency with each other. This study excavates the potential of EMIS method exploiting ZGV resonance modes for the damage characterization.