Daniel M. Warren
L. Dwynn Lafleur
F. Douglas Shields
Natl. Ctr. for Phys. Acoust., Coliseum Rd., University, MS 38677
The unimorph is a very popular piezoelectric transducer used in consumer products ranging from musical greeting cards to smoke alarms. Recently unimorphs have been used to construct low-frequency hydrophone projectors [D. M. Warren et al., J. Acoust. Soc. Am. 91, 2325 (A) (1992)]. Despite their popularity, no mathematical analysis adequately addresses this unique transducer. The unimorph is a bilaminate disk---one layer piezoelectric, the other metal. The metal layer has a larger radius than the piezoelectric and the thicknesses of the layers are not necessarily equal. Theoretical treatments of other flexural disk transducers, like the bimorph disk, assume layers of the same material [E. G. Thurston, J. Acoust. Soc. Am. 24, 656 (1952)], elasticity controlled by a single layer [T. D. Sullivan and J. M. Powers, J. Acoust. Soc. Am. 63, 1396 (1978)], or effective elastic constants to be measured experimentally [S. Hanish, NRL Rep. 5259 (1959)]. Furthermore, all assume equal radii. The current theory offers a more suitable treatment of a simply supported unimorph operating against a vacuum. Calculations of the surface velocity profile are compared to laser Doppler measurements. [Work supported by ONR.]