Ball to Separator Contact Forces in Angular Contact Ball Bearings

111 Pages·2000·2.15 MB·English

https://ntrs.nasa.gov/search.jsp?R=19780013526 2019-01-24T18:06:28+00:00Z
NASA ContractorR eport 2976
Ball to Separator Contact Forces
in Angular Contact Ball Bearings
UnderT hrust and Radial Loads
Lester J. Nypan
GRANT NSG3- 0 G 5
APRIL 1978
NASA
I
TECH LIBRARY KAFB, NM
NASA Contractor Report 2976
Ball to Separator Contact Forces
in AngularC ontactB allB earings
Under Thrusta ndR adial Loads
Lester J. Nypan
CaliforniaS tate University, Northridge
Northridge, California
Prepared for
LewisR esearch Center
under Grant NSG-3065
National Aeronautics
and Space Administration
Scientific and Technical
Information Office
1978

Table of Contents
Pape
Introduction 1
Separator Study Machine 2
TestB earings
SeparatorF orceT ransducer
ForceT ransducerC alibration
Experimental Procedure 7
Data Analysis 8
Results and Discussion 11
Conclusion 16
References 17
Appendix I Computer Program 102
iii
List of Figures
Figure Page
1 SeparaStto urd y Machine 18
2 TesB te ariniSgn e paratoSr t udy Machine 21
3 Ball ContaFco trT c rea nsducer 22
4 Sample ForTc rea nsducCe ar libration 23
5 Example of Photographs Taken 24
6 BaCl lo ntaFc to rces at 4000 rpm 25
7 Ball ContaFc ot rces at 8000 rpm 43
8 Ball ContaFc to rces at 12000 rpm 64
9 Variatioon f Magnitude of Cage Forces 73
with Speed-Radial Loads
10 Variation of Location of Cage Forces 77
with Speed-Radial Loads
11 Variation of Magnitude of Cage Forces 81
with Speed-ThrustL oads
12 Cage toI n ner Race Land ContacF to rce 84
13 Cage tIo n ner Race Land Clearance 86
Variation with Location
14 Cage tSo h aft Speed Ratios 91
iv
List of Tables
Table Page
Sp1eB cei afirci naTgtie osnt s 97
2 Speed, LoadSC paor nin ndSg t ants 98
3 SpCroi nnBgsa tea nandr ti sn gs Used 99
4 Calculated Number of ShRaf etv olutions 100
Between Photographs
5 MFoearscuer e Rda nges 101
V
Introduction
Currentd evelopments in jet engine technology are placing more
stringent demands on gast urbined esign.T here is a constantlyi n-
creasing requirement for engines to develop greater thrust outputs.
In addition to this increased loading the need to raise the thrust/weight
ratio of engines and to improve the fuel consumptionh as led to higher
rotors peedsa ndo peratingt emperatures,l ighter componentsa nd corres-
pondinglyi ncreaseds tructuralf lexibility.I na nticipationo ft o-
morrow's requirements,f urther advanced knowledge ofe ngine component
technology must be obtained.(l)*
In the case of rolling contact bearings there is a need for a
betteru nderstandingo fc age and rolling elementd ynamics, particularly
in ultra-high speed applications.(2,3,4,5)
Recently developed, advanced bearing theories have resulted in
computerized optimization of rolling element bearing designs and in
some casesa ccuratep rediction of bearingp erformance.T hesed evelop-
mentsa nda dvances byn om eans substitute for testing of rolling element
bearings which for many years was the basis for bearing development.
To the contrary, the need for more refined data gathering methods hasb e-
come obvious. Tests are needed tov erifyt het heories which form the
foundationo ft hesec omputerp rograms. Also, performance tests and
studies will alwaysb en eeded to refine bearing designs for critical
applications.
The interaction between the rolling elements of a bearing with
the racewaysa nd separators is particularly difficult to measured ue
-""
"Numbers in parentheses designate references at end of report.
to the rapidity of their motion. The kinematicb ehaviora ndt he
resulting forces acting on a rolling element/separator/raceway assembly
could in the past be measured only by tests where the operating condi-
tions were drastically simplified.
Separator Study Machine
An optical bearing test rig has been constructed to operate the
bearing and make photographic records of the rolling elements and
separator behavior. Figure la shows an overall viewo f the machine as
it is presently installed in the Dynamics Laboratory of the Engineering
Building at CaliforniaS tateU nT%ersity,N orthridge. The machine was
originally assembled by IndustrialT ectonics,I nc., Compton, Calif.,
and has been used in industrial bearing research, and in a ball motion
study reported in (6).
The bearing test rig is basically a shaft supported by a pair of
preloaded ball bearings at onee nda nd the test bearing at the other
end. One face of the test bearing is exposed to allow free view of
the balls and thes eparator. Radial load was applied to the test bearing
by a hydraulic actuator through a cable loop over the bearing housing.
The shaft was driven by a 75 hp hydraulic motor through a geared belt
drive, giving speeds infinitely variable from 100 to 15,000 rpm.
Figure lb is a schematic of the shaft assembly.
Lubricating oil for under race cooling and test bearing lubrication
is supplied through a series of orifices from the rear of the test
bearing.
Due to the high tangential velocities present when a bearing is
rotated at shafts peeds up to l5,OOO rpm, conventionalp hotograph
techniques are inadequate. The difficulty lies ino btaining photo-
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graphs having sufficient resolution for analysis when very short ex-
posures are required to freeze the motfon of the bearing elements.
This problem has been overcome by eliminating the gross rotational motion
using a derotationp rism. The resulting image thusp resentst hed ifferen-
tial motionb etween the separator and the rolling element, enabling ob-
servation and photographs to be made of an individual separator pocket.
Derotation is accomplished by synchronizing the rotation of a Pechan
prism at half-speed with the rotation of the ball separator, thus
causing the apparent image rotatbn and the true separator rotation
toc oincide. This results in the derotated imageo f thea reao fi nterest
being imaged on the film planeo f a camera.L ightr aysf romt hei llumi-
nated bearing are collected through the front window of the instrument.
This window is optically coated to reject ultraviolet energy produced
by ultraviolet lamps, serving the circuit for the prism speed control.
From the window, the rays travel through collimator lenses and the
Pechanp rismb eforet heyt ravelt hrought hee xitl enses.T heirp ath
i s then deflected by mirrors which fold the image in different directions.
Figure ICs hows light paths through the scanner.
One light trace travels to a beam splitter wherea pproximately
15 % of the light is reflected to the eyepiece optics to provide an
image observablet ot heo perator. The balance of lighte nterst he
aperture of the pulse camera.
Alignmenta nd positioning of the optical elements ensure that
the eyepiece observes the same image quality andf ormat as that which
the film sees.
Another image is foldeda ndd emagnified in the transfer lens
assembly before it enters the camera.
A derotated image of the luminous painted segment of the test
bearing separator is optically folded out and directed toward an
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image splitting mirror swface wedce which proportions the light enterin5
two photomultipliert ubep hotocathodes. The electronics ignals from
these tubes are used by the tracking system to control the prism speed.
A trackings ystemh oldst he imageo f a selected point at the test
bearings eparatori nt hef ieldo f view. It will accommodate a variation of
up to 10% of a fixed ratio ofs eparator-to-shafts peedw ithout loss of
the ability to lock onto the proper position within one revolution of
the bearing retainer.
It is necessary to sense the tracking error in angular position
of thed erotationp rismt op rovide an input for thes ervos ystem.T his
error signal is provided in the form of the difference in output of
two multiplier phototubes.
A sector on the bearing retainer is coated with fluorescent paint
and illuminatedw ithu ltravioletl ight. An image of thes ectoro fa rc
is formed in a plane containing the apex of a mirror surface wedge.
The light striking the two surfaces of the wedge is reflected and illu-
minatest hep hotocathodeo ft hep hotomultipliert ubes.R otation of
the prism results in a displacemento ft he image and a consequenti n-
crease in the output ofo ne tube and decrease in the output of the other.
Electronic filtering is provided to discriminate between the
steady signal due to the ultraviolet excitation of the phosphora nd
any intermittent excitation due to strobe lamps to reducea nyi nteraction
between the level of light striking the phosphora nd the error signal
produced by the photomultipliers.
Four Chadwick-HehuthS trobexl amps are flashed at the 16-frame-
per-secondc amera rate to illuminate the separator and to stop the
images of the protractors on the inner and outer races of the bearing
so that angular position information is recorded on thep hotographs.
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