Thin-Layer Prestressed Composite Ferroelectric Driver and Sensor Characterization with Application to Separation Flow Control

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%

Piezoelectric Composites as Bender Actuators

ABSTRACT Lead Zirconate Titanate, PZT, layered into a composite with different materials, produces pre-stressed, curved, devices capable of enhanced displacement. This study focuses on Thunder and Lipca which are built using different combinations of constituent materials. Thunder devices consist of layers of aluminum, PZT, and stainless steel bonded with a hot-melt adhesive. Lipca devices consist of carbon and fiberglass layers with a PZT layer sandwiched in between them. Measuring out-of-plane displacement under load as a function of temperature is used to evaluate field-dependent stiffness. Results show that Lipca devices have higher stiffness than Thunder at 24 • C, but lower at other temperatures

Radial-Electric-Field Piezoelectric Diaphragm Pumps

In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port

Tour the United VCU, The Premier Urban Research University

This project will capitalize on the existing Open House weekends by offering a 60 minute tour of the MCV Campus. The tour will expose prospective students to VCU as a whole, highlighting the diverse range of studies and to present VCU as one university. The bus ride and walking tour will showcase the connection and relevance of both campuses, allowing prospective students with a myriad of interests to see all that VCU has to offer

Characterization of Piezoelectric Actuators for Flow Control over a Wing

During the past decade, piezoelectric actuators as the active element in synthetic jets demonstrated that they could significantly enhance the overall lift on an airfoil. However, durability, system weight, size, and power have limited their use outside a laboratory. These problems are not trivial, since piezoelectric actuators are physically brittle and display limited displacement. The objective of this study is to characterize the relevant properties for the design of a synthetic jet utilizing three types of piezoelectric actuators as mechanical diaphragms, Radial Field Diaphragms, Thunders, and Bimorphs so that the shape cavity volume does not exceed 147.5 cubic centimeters on a 7centimeter x 7centimeter aerial coverage. These piezoelectric elements were selected because of their geometry, and overall free-displacement. Each actuator was affixed about its perimeter in a cavity, and relevant parameters such as clamped displacement variations with voltage and frequency, air velocities produced through an aperture, and sound pressure levels produced by the piezoelectric diaphragms were measured

Proceedings of the ASME 2010 Conference on Smart Materials, Adaptive Structures, and Intelligent Systems SMASIS2010 SMASIS2010-3688 DRAFT FEASIBILITY OF USING PIEZOELECTRIC PROBES TO MEASURE VISCOSITY IN NEWTONIAN FLUIDS

ABSTRACT Viscosity plays an important role in modeling fluid flow in different systems. In Newtonian fluids, viscosity is a constant, measureable property. Currently, viscosity is measured using viscometers that use an array of different techniques depending on the application. In this study, pre-stressed lead zirconate titanate (PZT) composites were used as probes to monitor changes in viscosity. The probes are used as an actuator-sensor pair: a voltage of 1V rms will be applied to one probe, the actuator; the second probe, the sensor, receives a vibration wave and turns it into an output voltage. Measurements of gain and phase at different input signal frequencies are analyzed. The fluid-medium where the probes are tested consists of different glycerin-deionized water solutions. Results indicate that the frequency of peak phase shift can be correlated to fluid viscosity. This correlation is exponential with viscosity, with an R 2 of 0.99. Results included viscosity values in the range of 0.8cP to 612cP. Possible applications for this type of sensor are numerous, and are both non-time-dependent (simple viscosity measurements of fluids), and time-dependent

Non-Destructive Evaluation Device for Monitoring Fluid Viscosity

There is an increasing need for non-destructive, low-cost devices for real-time fluid viscosity monitoring. Therefore, in this study, a method based on structural health monitoring is adapted for monitoring fluid properties. A device is built such that an inexpensive and disposable viscosity probe be possible. The design incorporates a sensor/actuator pair using a piezoelectric material layered with copper/brass and capable of monitoring viscosity changes in low volume liquids (e.g., vacutainer vial). Experiments performed with the new device show a definite pattern of wave propagation in viscous solutions. A numerical model is built to investigate the wave propagation in the fluid. For experimental measurements, the sensor part of the device detects the generated pressure wave in fluid (e.g., air, water, glycerin) by the actuator part. The phase shift between the actuator and the sensor signals is then recorded and plotted for different concentrations of glycerin and water at room temperature. The results of this study show a direct correlation between the phase shift and varying viscosity in the ultrasonic frequency range from 6 to 9 MHz. The numerical simulation, performed utilizing acoustic modal and harmonic response analysis, results also demonstrate the same trend as the experimental results: a phase shift increases with the viscosity of the fluid

Vibration Viscosity Sensor for Engine Oil Monitoring Using Metal Matrix Piezoelectric Composite

Lubricants such as engine oil play an important role in preventing machine wear and damage. Monitoring the deterioration of lubricating oils is a significant technical issue in machine maintenance. In this study, a sensor for monitoring engine oil viscosity was developed using a metal-core piezoelectric fiber/aluminum composite. This composite is a piezoelectric ceramic that is reinforced by a metal matrix; it is expected to be utilized in harsh environments such as the inside of an engine. An active type measurement method was employed to monitor variations in the viscosity of glycerin solution as a model liquid. In this method, a self-generated vibration is correlated to the viscosity of a liquid by measuring the damped vibration amplitude and the variation in the resonance frequency. The results showed that the vibration had a high sensitivity to the liquid viscosity; further, it was observed that the shift in resonance frequency correlated to a wider range of measurable viscosity. Both measured parameters indicate that the metal-core piezoelectric fiber/aluminum composite is a viable sensor for engine oil monitoring