Dependence of Piezoelectric Discs Electrical Impedance on Mechanical Loading Condition.

The piezoelectric effect, along with its associated materials, fascinated researchers in all areas of basic sciences and engineering due to its interesting properties and promising potentials. Sensing, actuation, and energy harvesting are major implementations of piezoelectric structures in structural health monitoring, wearable devices, and self-powered systems, to name only a few. The electrical or mechanical impedance of its structure plays an important role in deriving its equivalent model, which in turn helps to predict its behavior for any system-level application, such as with respect to the rectifiers containing diodes and switches, which represent a nonlinear electrical load. In this paper, we study the electrical impedance response of different sizes of commercial piezoelectric discs for a wide range of frequencies (without and with mechanical load for 0.1-1000 kHz with resolution 20 Hz). It shows significant changes in the position of resonant frequency and amplitude of resonant peaks for different diameters of discs and under varying mechanical load conditions, implying variations in the mechanical boundary conditions on the structure. The highlight of our work is the proposed electrical equivalent circuit model for varying mechanically loaded conditions with the help of impedance technique. Our approach is simple and reliable, such that it is suitable for any structure whose accurate material properties and dimensions are unknown.