Analysis of shear modes in a piezoelectric vibrator

A shear piezoelectric vibrator has been analyzed in detail. There are two types of shear motion associated with the same shear stain deformation. It is found experimentally that the lower frequency mode among the two has lower strength and its vibration amplitude continuously decreases as the long dimension of the vibrator increases. A nearly pure shear mode may be obtained with the aspect ratio greater than 20, but the influence of the other low frequency mode could not be totally eliminated even at such a large aspect ratio. We found that such phenomena can be understood by the conservation of angular momentum and the shared origin of these two types of shear motion. The ratio of the driving forces for these two types of shear motion is related directly to the aspect ratio of the vibrator. Formulas for calculating k(15) from the resonant and antiresonant frequencies using both type of shear modes are given. (C) 1998 American Institute of Physics.