M.S. Thesis Presentation by Brandon Witt Davis
Wednesday, April 28, 1999

(Dr. Christopher Lynch, advisor)

"Constitutive Behavior and Reliability of Actuator Materials"


The purpose of the current investigation is to experimentally characterize the behavior and reliability of actuator materials.  This research focuses on two types of ferroelectric materials; piezoelectric and electrostrictive ceramics.  Piezoelectric and electrostrictive ceramics are materials which can convert electrical energy into mechanical energy.  It is this property which lends these materials to actuator applications.  Actuator devices made from these materials deliver small but accurate displacements with a fast response time.

To effectively design and fabricate piezoelectric actuators, we must evaluate and understand the materialís response under conditions simulating operational environments which are representative of the application.  Areas which need to be evaluated include, mechanical response to large stresses, large electric fields, polarity switching behavior, temperature response, and fatigue behavior.

Combined compressive stress/electric field loadings at various temperatures are performed to examine the actuation behavior. The materials are received and tested in several different forms:  bulk materials, stack actuators, and multilayer actuators.  Several different compositions ranging from soft to hard and single grain to fine grain are examined.  Uniaxial compressive stress tests are conducted to -125 MPa with electric field cycles of + 2 MV/m every 25 MPa at 25o C and 100o C.  The fatigue life of the actuators is examined at maximum actuation conditions.  The results of the tests are used to construct a database for analyzing the constitutive behavior of the actuator materials.