A method for measuring electrostrictive properties of ultrasonic transducer material under high hydrostatic pressure

Abstract

The motional impedance or admittance method cannot be applied to a test transducer contained in a small non‐sound‐absorbing pressure tank, because admittance or impedance loop does not make a circle due to sound reflection at the tank wall. The method we used is to excite a bar‐shaped test transducer in a pressure tank into longitudinal vibration by the use of a mechanical driving system, and to observe short‐circuit current or open‐circuit voltage of the test transducer. A transducer material for high power use was taken as a sample. Electrostrictive stress constants e31, h31 and dielectric constant ε31 were measured at hydrostatic pressures from 1 to 600 atm. Vibrational velocity dependence of e31 and h31 was also measured, varying driving velocity level at the test transducer end as high as 80 cm/s. The results are that e31 and h31 become slightly large as hydrostatic pressure increases but show no appreciable velocity level dependence.