TABLE OF CONTENTS In certain applications there are electronic devices sealed in an armor for operations in hazardous environments where physical access to the devices is prohibited. There is a need for periodically recharging the batteries inside the armor that power the devices. Piezoelectric transducers may be used to generate acoustic waves propagating through the armor for transmitting a small amount of power to the devices inside the armor. In this section we examine the performance of such a power transmission technique.
Consider the structure illustrated in Fig. 13.1.1, in which a metal plate representing the armor is sandwiched by two piezoelectric layers. These piezoelectric layers model two piezoelectric transducers, one for generating acoustic waves driven by a prescribed electric voltage source and the other for converting the acoustic energy into electric energy to power a load circuit, characterized by its impedance Z L as indicated in the figure.
Consider thickness-stretch vibrations. For motions of the ceramic layers we have
The driving transducer is electroded on its outer surface at x 3= h 0+ h 1. The electrode is subjected to a time-harmonic driving voltage V 1 (t), and the mechanical boundary condition is traction-free. These require that
The current density flowing out of the driving electrode at x 3= h 0+ h 1 is given by
where Q 1 is the charge per unit area on the electrode.
