In-Plane Torsional Piezoelectric Discal Resonator And Its Application In Viscosity Measurement Of Liquids

Recently, torsional piezoelectric resonators are widely used in the fields of pre-cise transducers and advanced actuator, such as ultrasonic motors, piezoeletric pumps, optical scanners and energy recovery devices. Majority of current resonators are sub-stantively cylindrical type structures with axial torsion abilities, this paper proposes a discal piezoceramic resonator with spiral interdigited electrodes (SEDEs) that can ef-fectively generate in-plane torsional displacement. It has a simple structure, performes reliably and can be conveniently constructed. Meanwhile, the application of torsional resonator in liquid viscosity measurement is explored. With the advantage of small size, simple stucture, cheap price, and on-line operating capability, the propsoed device is expected to be a powerful competitor for portable viscometer.Two typical types of the piezoelectric resonator with SIDEs, constant electrode spi-ral angle and constant pitch between adjacent electrodes, are proposed, and their work-ing principle is studied. From basic piezoelectric equation, the torsional displacemene and controlled equation are derived. The stactic torsional displacement and in-plane tor-sional resontant frequency under different values of a and b are introduced. The finite element simulation method for piezoelectric resonators under the condition of complex polarization is provided. The static, modal and harmonic resonse analysis are imple-mentated to study the properties of proposed resonators. The prototype resonators are fabricated and tesed. The results between experiment and simulation are comparied. Finally, the prototype viscometer is fabricated and tested in glycerol/water solutions. Simultaneously, the measure method of viscosity based on impedance analysis is pre-sented. With a driving voltage of400Vp-p at1Hz, the maximum quasi-static torsional angles are0.00458°for Type I resonator and0.00605°for Type Ⅱ resonator at the radius of6mm. With a driving voltage of10Vp-p, the amplitudes of torsional vibrations at the radius of6mm are0.00105°at86.0kHz for Type I resonator and0.00149°at84.4kHz for Type II resonator at the first in-plane torsional vibration modes. Experiment results show a good linear relation between dynamic resistance R2and (?)ρμ with a R-square of0.9979. The linearity between△f and (?)ρμ declines with a R-square of0.9763.