Piezoceramic disc

A simple form of accelerometer is shown in Fig. 6.23(a). During acceleration in the direction of poling the mass exerts a force, F (= M x ace11) on the piezoceramic disc and therefore a stress of F/A where A is the area of the disc. The measured voltage output is proportional to the acceleration. 

A piezoceramic disc, thickness t and diameter D, is electroded over its faces and poled. A constant voltage is applied in the sense that t increases in an unrestrained way. From a consideration of the energies involves in the definition of k33 derive the relationship ... 

The following electroded pieces fabricated from the same piezoceramic are available (i) a disc - diameter 21 mm, thickness 0.8 mm, fully poled through its thickness, (ii) a square section rod 20x3x3mm fully poled along its length, and (iii) a rod of the same dimensions as in (ii) but fully poled perpendicular to its length. 

An experimental 1-3 piezoceramic/polymer composite disc transducer operating at the fundamental thickness mode resonance frequency is intended to detect objects in water having dimensions of approximately 10 mm. It is firmly fixed to a backing. 

The ultrasonic transducer was a PZ26 piezoelectric ceramic disc (Ferroperm Piezoceramics A/S, Kvistgard, Denmark). The tranducer should be designed to operate in the region of the resonance frequency of the resonator channel. 

PWAS are made of thin, inexpensive piezoceramic wafers electrically poled in the thickness direction and provided with top and bottom electrodes. Typical PWAS are 7 mm squares or discs with a 0.2 mm thickness (Figure 16.6). PWAS can be bonded to the stmcture with strain gauge installation methodology. They have also been experimentally inserted between the layers of a composite layup, but this option has raised some structural integrity issues that are stiU being examined. The PWAS transducers are called differently by various authors piezos, piezo wafers, piezo wafer transducers or PZTs, etc. In this chapter, we will consistently call them PWAS (same in singular and in plural) or PWAS transducers. ... 

---