Engineering topics

Hellbaum, Richard F.

Publications and source records attributed to Hellbaum, Richard F..

14 records

NASA NTRS2007

Method of Fabricating a Composite Apparatus

A method for fabricating a piezoelectric macro-fiber composite actuator comprises making a piezoelectric fiber sheet by providing a plurality of wafers of piezoelectric material, bonding the wafers together with an adhesive material to from a stack of alternating layers of piezoelectric material and adhesive material, and cutting through the stack in a direction substantially parallel to the thickness of the stack and across the alternating layers of piezoelectric material and adhesive material to provide at least one piezoelectric fiber sheet having two sides comprising a plurality of piezoelectric fibers in juxtaposition to the adhesive material. The method further comprises bonding two electrically conductive films to the two sides of the piezoelectric fiber sheet. At least one conductive film has first and second conductive patterns formed thereon which are electrically isolated from one another and in electrical contact with the piezoelectric fiber sheet.

Wilkie, W. Keats↗

NASA NTRS2004

Thin layer composite unimorph ferroelectric driver and sensor

A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

Hellbaum, Richard F.↗

NASA NTRS2003

Method of Fabricating a Piezoelectric Composite Apparatus

A method for fabricating a piezoelectric macro-fiber composite actuator comprises providing a piezoelectric material that has two sides and attaching one side upon an adhesive backing sheet. The method further comprises slicing the piezoelectric material to provide a plurality of piezoelectric fibers in juxtaposition. A conductive film is then adhesively bonded to the other side of the piezoelectric material, and the adhesive backing sheet is removed. The conductive film has first and second conductive patterns formed thereon which are electrically isolated from one another and in electrical contact with the piezoelectric material. The first and second conductive patterns of the conductive film each have a plurality of electrodes to form a pattern of interdigitated electrodes. A second film is then bonded to the other side of the piezoelectric material. The second film may have a pair of conductive patterns similar to the conductive patterns of the first film.

Wilkie, W. Keats↗

NASA NTRS2000

Ferroelectric Pump

A ferroelectric pump has one or more variable volume pumping chambers internal to a housing. Each chamber has at least one wall comprising a dome shaped internally prestressed ferroelectric actuator having a curvature and a dome height that varies with an electric voltage applied between an inside and outside surface of the actuator. A pumped medium flows into and out of each pumping chamber in response to displacement of the ferroelectric actuator. The ferroelectric actuator is mounted within each wall and isolates each ferroelectric actuator from the pumped medium, supplies a path for voltage to be applied to each ferroelectric actuator, and provides for positive containment of each ferroelectric actuator while allowing displacement of the entirety of each ferroelectric actuator in response to the applied voltage.

Jalink, Antony, Jr.↗

NASA NTRS2000

Advanced Layered Composite Polylaminate Electroactive Actuator and Sensor

The present invention relates to the mounting of pre-stressed electroactive material in such a manner that large displacement actuators or sensors result. The invention comprises mounting the pre-stressed electroactive material to a support layer. This combination of a pre-stressed electroactive material and support layer may in turn be attached to a mounting surface. The pre-stressed electroactive material may be a ferroelectric, pyroelectric, piezoelectric, or magnetostrictive material. The size, stiffness, mass, and material of the support layer is selected to result in the electroactive device having dynamic response properties, environmental capability characteristics, and the required resilience optimized for a given application. The capacity to connect the support layer to a surface expands the arenas in which the prestressed electroactive device may be used. Application for which the invention may be used include actuators, sensors, or as a component in a pumps, switches, relays, pressure transducers and acoustic devices.

Fox, Robert L.↗

NASA NTRS1999

Ferroelectric Fluid Flow Control Valve

An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

Jalink, Antony, Jr.↗

NASA NTRS1999

Ferroelectric Stirling-Cycle Refrigerator

A Stirling-cycle refrigerator has a three-pump configuration and pumping sequence, in which one pump serves as a compressor. one pump serves as an expander, and one pump serves as a displacer. The pumps are ferroelectrically actuated diaphragm pumps which are coordinated by synchronizing the ferroelectric-actuator voltages in such a way that the net effect of the displacer is to reduce the deleterious effect of dead space; that is, to circulate a greater fraction of the working fluid through the heat exchangers than would be possible by use of the compressor and expander alone. In addition. the displacer can be controlled separately to make the flow of working fluid in the heat exchangers turbulent (to increase the rate of transfer of heat at the cost of greater resistance to flow) or laminar (to decrease the resistance to flow at the cost of a lower heat-transfer rate).

Jalink, Antony, Jr.↗

NASA NTRS1998

High Displacement Solid State Ferroelectric Loudspeaker

A piezoelectric loudspeaker suitable for midrange frequencies uses a dome shaped piezoelectric actuator to a speaker membrane directly is discussed. The dome shaped actuator is made from a reduced and internally biased oxygen wafer, and generates excursion of the apex of the dome in the order of 0.02-0.05 inches when a rated drive voltage of 350 V rms is applied between the convex and the concave surface of the dome shaped actuator. The load capacity exceeds 10 lbs. The edge of the rim of the dome shaped actuator must be free to rock when the dome height varies to ensure low distortion in the loudspeaker. This is achieved by mounting the rim of the dome shaped actuator on a support surface by prestress only. An exceptionally simple design uses a planar speaker membrane with the center part of one side pressed against the rim of a dome shaped actuator by prestress from a stretched latex surround member.

Regan, Curtis R.↗

NASA NTRS1997

Thin Layer Composite Unimorph Ferroelectric Driver and Sensor

A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

Hellbaum, Richard F.↗

NASA NTRS1995

Improved Piezoelectric Loudspeakers And Transducers

Loudspeakers and related acoustic transducers of improved type feature both light weight and energy efficiency of piezoelectric transducers and mechanical coupling efficiency. Active component of transducer made from wafer of "rainbow" piezoelectric material, ceramic piezoelectric material chemically reduced on one face. Chemical treatment forms wafer into dishlike shallow section of sphere. Both faces then coated with electrically conductive surface layers serving as electrodes. Applications include high-fidelity loudspeakers, and underwater echo ranging devices.

Regan, Curtis Randall↗

NASA NTRS1994

Piezoelectric loudspeaker

A piezoelectric loudspeaker suitable for midrange frequencies uses a dome shaped piezoelectric actuator to drive a speaker membrane directly. The dome shaped actuator is made from a reduced and internally biased oxygen wafer, and generates excursion of the apex of the dome in the order of 0.02 - 0.05 inches when a rated drive voltage of 350 V rms is applied between the convex and the concave surfaces of the dome shaped actuator. The load capacity exceeds 10 lbs. The edge of the rim of the dome shaped actuator must be free to rock when the dome height varies to ensure low distortion in the loudspeaker. This is achieved by mounting the rim of the dome shaped actuator on a support surface by prestress only. An exceptionally simple design uses a planar speaker membrane with the center part of one side pressed against the rim of a dome shaped actuator by prestress from a stretched latex surround member.

Regan, Curtis Randall↗

NASA NTRS1994

High-Temperature Microphone With Fiber-Optic Output

Acoustic-pressure transducer (microphone) with fiber-optic output designed to withstand hot, loud, structurally vibrating environment like that of jet engine. Features flat frequency response out to frequencies well beyond several-kilohertz range needed to test for acoustic-pressure loads on engine structures.

Hellbaum, Richard F.↗

NASA NTRS1992

An interferometer having fused optical fibers, and apparatus and method using the interferometer

An interferometer includes a first optical fiber coupled to a second optical fiber by fusing. At a fused portion, the first and second optical fibers are cut to expose respective cores. The cut or fused end of the first and second optical fibers is arranged to oppose a diaphragm or surface against which a physical phenomenon such as pressure or stress, is applied. In a first embodiment, a source light which is generally single-mode monochromatic, coherent light, is input to the first optical fiber and by evanescence, effectively crosses to the second optical fiber at the fused portion. Source light from the second optical fiber is reflected by the diaphragm or surface, and received at the second optical fiber to generate an output light which has an intensity which depends upon interference of reference light based on the source light, and the reflected light reflected from the diaphragm or surface. The intensity of the output light represents a positional relationship or displacement between the interferometer and the diaphragm or surface.

Hellbaum, Richard F.↗

NASA NTRS1990

Air-Velocity Sensor For Helicopter

New airspeed sensor conceived for accurate measurement of both airspeed and direction of flight of helicopter. Direction of motion of helicopter displayed by lighting of one of series of lamps encircling digital display of airspeed. Pressure transducer measures difference between impact and static pressures at tip of rotor blade by use of conventional pitot-static-tube assembly.

Garner, H. Douglas↗