Understanding the coupled electromechanical response of a PZT patch attached to concrete: Influence of substrate size

The influence of the substrate size on the coupled dynamic electromechanical (EM) response of a PZT (Lead Zirconate Titanate) patch attached to a concrete substrate and the scaling of the response with size are investigated using an approach which combines experimentation with numerical simulations. The dynamic response of the PZT patch is investigated for an applied electrical potential, which is applied at multiple frequencies. The electrical conductance spectrum of the bonded PZT patch contains narrow, closely-spaced, local peaks, which exhibit dependence on the size of the substrate. The closely spaced peaks in the electrical conductance response of a PZT patch bonded to a concrete cube are identified with the structural modes of the cube. The local peaks are superimposed over the baseline EM response of the bonded PZT patch. The resonant behavior of the bonded PZT patch is identified in the baseline EM response, which is determined by the dimensions of the PZT patch, its elastic material properties and the stiffness of the substrate medium. The dynamic response of a PZT patch attached to a finite-sized substrate is influenced by the mechanical impedance to its motion arising from the structural motion of the cube and the dynamic impedance offered by the substrate material. As the size of the concrete substrate increases, the structural peaks are damped and diminish in amplitude relative to the amplitude of the resonant peaks of the bonded PZT patch. For each resonant mode of the bonded PZT patch in the electrical conductance spectrum, there is a finite zone of influence beyond which the influence of the boundary is insignificant. The zone of influence is smaller for PZT resonant modes of higher frequency. For physical dimensions of the substrate smaller than the zone of influence of the resonant mode, the structural modes of the substrate are superimposed on the resonant mode of the bonded PZT patch.