Transducer amplifies vibrations produced by piezoelectric drivers, creating greater amplitudes than were possible with direct drive devices. Drivers isolated from bearing surfaces result in bearings with high axial load capacity and stiffness, thus, wear on ceramic cylinders is reduced

Hoogenbloom, L.

English

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May 1971 CORRECTED COPY 
NASA TECH BRIEF 
Marshall Space Flight Center
Brief 71-10140 
H 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Improved Transducer for Squeeze-Film Bearings 
A piezoelectrically driven, vibrating transducer is encountered, require that at least one bearing sur-
for squeeze-film bearings amplifies the vibrations face vibrate transversely. Because of the viscosity of 
produced by the piezoelectric drivers, producing the bearing fluid (commonly air) and the nonlinear 
Body End
nature of the squeeze motion, the gas pressure within 
Solid	 the film rises above the ambient pressure. This 
Â .ø—, Center pressure differential determines the bearing's load-
carrying capacity, and is largely a function of the 
vibrational frequency and amplitude. The most critical 
element, then, in a squeeze-film bearing is the trans-
ducer, which must provide a high-frequency, large-
amplitude squeeze motion. The transducer design 
(see fig.) shown in cross section uses multiple piezo-
electric cylinders arranged radially around the axis 
of the transducer body. The shape of the body end 
pieces, shown conical in the figure, may be varied 
according to the geometry of the bearing. Circular 
A Sol id. Center grooves in the body produce weakened portions 
between the ends and the body center. These areas 
amplify the vibrations produced in the transducer. 
Six radial 2.54 cm (1 in.) diameter holes are 
bored in the central plane of the transducer body. 
Three are shown filled with ceramic drive cylinders 
shrink fitted onto solid 1.9 cm (0.75 in.) diameter 
metal posts. The posts support the drivers, as well 
as providing them with one electrical contact. The 
Section A-A	 drivers are slit radially to relieve hoop stress caused 
by the shrink fitting. 
greater amplitudes than were possible with direct-
drive devices. The drivers themselves are isolated 
from the bearing surfaces, resulting in a squeeze-film 
bearing with high axial load capacity and stiffness. 
As a result of these two modifications, the wear 
on the ceramic cylinders is considerably reduced com-
pared to previous operation. 
Gaseous squeeze-film bearings, commonly used in 
devices such as gyroscopes, where high-speed rotation 
Ah (continued overleaf) 
This documetct was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately ownedrights. 
The drivers are poled in the radial direction so 
that they drive the body through a cyclic expansion 
in length. This axial excursion is amplified by flexure 
in the weakened portions of the body, and is then 
applied to the end pieces. Note that the dimensional 
stability of the drivers does not affect the bearing 
caps. Also, because the thickness of the drivers is 
much less than their radius, dimensional changes in 
the drivers do not affect the shrink fit.
https://ntrs.nasa.gov/search.jsp?R=19710000139 2020-03-17T02:24:10+00:00Z
With the arrangement shown, three resonance modes 
exist, at 11, 18, and 27 kHz. With all six posi-
tions filled, only the two lower-frequency modes are 
detected. The 27 kHz mode is very powerful, 
yielding excursions of about 0.0015 um (600 Mm.) 
peak-to-peak at the cone tips, and has the additional 
advantage of being above the audible frequency band. 
Notes: 
1. Additional information on squeeze-film bearings 
may be found in NASA tech briefs B66-10226 
and B68-10180. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: TSP71-10140
Patent status: 
Title to this invention has been waived under the 
provisions of the National Aeronautics and Space Act 
(42 U.S.C. 2457 (1)), to Mechanical Technology Inc., 
968 Alban'-Shaker Rd., Latham, New York 12110. 
Source: L. Hoogenbloom of

Mechanical Technology Inc. 
under contract to
Marshall Space Flight Center

(M FS-20826)
.. 
Brief 71-10140	 Category 07


Improved transducer for squeeze-film bearings

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