Date of Award

Spring 1998

Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

Committee Director

Gregory V. Selby

Committee Member

Linda L. Vahala

Committee Member

Jen-Kuang Huang

Committee Member

A. Sidney Roberts, Jr.

Committee Member

Robert G. Bryant


Experiments were conducted in two different stages--general piezoelectric actuator characterization and flow separation control applications. The characterization of the piezoelectric devices was performed in several stages, due to the many variables that affect performance. The first stage of the characterization consisted of tests conducted on 13 different THUNDERTM (thin-layer composite unimorph ferroelectric driver and sensor) configurations. These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25μ thick aluminum as backing material, with and without a top layer of 25μ aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions of 5.1 x 3.8 x 0.018 cm. The above configurations were tested at two stages of the manufacturing process: before and after re-poling. The parameters measured included frequency, driving voltage, displacement, capacitance, and radius of curvature. An optical sensor recorded the displacement at a fixed voltage (100-400 Vpp) over a predetermined frequency range (1-1000 Hz). These displacement measurements were performed using a computer that controlled the process of activating and measuring the displacement of the device. A parameter was defined which can be used to predict which configuration will produce maximum displacement for a partially constrained device. The second phase of the characterization was conducted using two different types of piezoelectric devices. Actuators were made with PZT wafers of 3.8 x 1.9 x 0.025cm, and 3.8 x 1.3 x 0.02 cm. These models consisted of a combination of top layers of 1 mil (0.0254 mm) aluminum and brass, and bottom layers of stainless steel, aluminum, and brass of varying thickness (3, 4, 5, 7, 9, 10 mil (0.076, 0.102, 0.127, 0.178, 0.229, 0.254 mm)). Displacement was measured for 12 configurations at 1 Hz and 200 Vpp under loads of 0, 0.2, 0.4, 0.5, and 1.0 Kg using an optical sensor. Again the parameter β was used to predict the configuration with the maximum displacement for a partially constrained device, as well as with the device under load. Finally, a THUNDERTM based actuator was used to deploy submerged vane-type vortex generators which were used to control turbulent separated flow associated with flow over a backward-facing ramp. Effectiveness of the vortex generator array was demonstrated using wall pressure measurements, velocity surveys, and smoke-oil flow visualization photographs which showed that the nominal flow separation region was reduced by 35-40%.