Date of Award

Summer 2000

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Advisor

Joshi, Srinivas G.

Second Advisor

Hock, Jeffory L.

Third Advisor

Richie, James E.

Abstract

Several workers have previously investigated the influence of viscosity on bulk acoustic waves (BAW) and surface acoustic waves (SAW). In this work, analysis of the influence of viscosity on Lamb waves propagating in thin plates of piezoelectric materials is investigated. The presence of liquid modifies the propagation velocity of the Lamb waves and the viscosity of the liquid produces attenuation of the waves. The appropriate boundary conditions at the interface are presented and theoretical analysis is done for the change in velocity and attenuation as a function of viscosity. Computational methods are used to simulate the effects of various acoustic modes at the interface between various piezoelectric materials and liquid media. The results of the simulations are studied in this work for various piezoelectric materials like, lithium niobate (LiNb03), lithium tantalate (LiTa03), lead zirconate titanate (PZT) and bismuth germanium oxide (Bi12Ge020). This work can be used effectively in design and analysis of Lamb wave sensors for determining the viscosity of fluids over a wide range of viscosity. The results show that for definite ranges of normalized viscosity "formula" and for different values of plate thickness 'formula" S0 wave is most suitable for development of different sensors and devices operating in contact with viscous liquid without significant attenuation.

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