TRANSIENT-RESPONSE OF PIEZOELECTRIC DISKS TO APPLIED VOLTAGE PULSES

Most of the techniques commonly used to analyse the vibration characteristics of piezoelectric discs are one-dimensional and assume that the piezoelectric disc vibrates in the thickness direction only (piston-like motion). They are applicable to discs with either very large diameter to thickness (D/T) ratios or very small D/T ratios. However, at intermediate D/T ratios, other vibration modes are significant, particularly in the transient motion when the disc is excited by voltage pulses. In this paper, finite element methods and modal analysis techniques have been used to predict the transient mechanical displacement over the surface of piezoelectric discs when they are excited by voltage pulses across electrodes on their top and bottom surfaces. Although many modes are predicted, and no one of them has the piston-like motion assumed by the one-dimensional model, the predicted transient response shows that the disc may display piston-like motion over the first few periods of the major through thickness mode due to high modal density and modal coupling effects. The surface motion then becomes complicated since other lower frequency modes come into effect. Finally the surface motion tends to that of the first radial mode, which is the last mode to be dampled out.