ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
1 Bearing Serial Number of Wear Depth Range  Number Flights (micro meter)  V6M002 20 5.08  V6L009 20 2.23  V89E006 19 2.23  V6L007 30 2.03  V6L025 32 1.27  V6M014 30 2.03  V6L013 32 Wear debris build-  UP  V6L001 19 .38 -. ::. . . . . . .- ,  . . ..>  Microscopic Observations  Mild discoloration  Black complex oxide on balls and  wear track  Light gold color discoloration  Superficial rust stains  Slightly darken balls  Moderate surface distress  corrosion  Moderate surface distress,  discoloration likely to lubricant  degradation  Ball banding and mild discoloration  and balls and races Figure 11 b. Metallographic section of black bearing  Metrology of Previously Flown Flight Bearings  After the discovery of the bearing with the blackened balls, seven additional BF shaft bearings were  microscopically inspected and the wear depth profiles were measured. Wear was measured using a form-  Talysurf measurement machine. Microscopic examination and wear depth results for these bearings are  reported in Table 1. The bearings had mild surface distress but no spalling. The bearings appeared to be  highly loaded with ball tracks running near the raceway shoulder. The balls showed discoloration,  superficial rust stains but only S/N V6L009 was contained the black tribological coating on the ball and  race wear surfaces. Metrology results show that Shuttle flights produced wear depths ranging up to 5  micrometers. The most damaged bearing was S/N V6M002. This bearing had 5 micrometers maximum  wear on the inner race with evidence of plastic deformation in raceways.  Table 1. Results of Metrology of Flight Body Flap Actuator Shaft Bearings  106  259
Bearing Testing of Body Flap Actuator Bearings  A pre-existing test rig (Figures 12 and 13) was adapted to conduct life tests on the body flap output Shaft  bearings (Size 106). The bearing tester supported an angular-contact bearing on each end of the drive  shaft. Axial load was applied to the bearing pair and shaft by a locking mechanical screw. A drive pulley  was attached to the middle of the drive shaft and was driven by a variable-speed AC motor. The bearing  housing temperature was controlled by circulating ethylene glycol through coolant passages in the  bearing test housings, which raised the test bearing temperature up to 70°C. During testing, the bearing  axial load, shaft rotational speed, motor amps, and temperature of bearing outer races were monitored  and recorded.  I  Figure 12. MSFC Bearing Test Rig -  Figure 13. Close-up view of MSFC Bearing Testing Rig  48 Mission Life Test Results at 60°C  The objective of the testing was to demonstrate that previous flown and re-lubricated was acceptable for  12 additional shuttle flights with a safety factor of 4. The temperature of 60°C was selected because it  260
was thought that Braycote 601EF grease was shorter at higher temperature and 60°C was the highest  and only temperature recorded in BF actuator system, namely in the power distribution unit.  Test Serial Number Max. Wear Depth during Flight  Simulation (micro meter)  BF-001 .66  BF-003 4.45 The life test conditions for a single mission were derived from the flight load spectrum for the body flap  actuator as understood early in the test program. The body flap qualification test load spectrum was made  worst case to establish the single-mission life test load profile for the body flap input shaft bearings shown  in Table 1.  MSFC Life Max. Wear after 48 mission  (micro meter) Test Number life test  LT002 2.54  LT002 5.72 Table 2. Single Mission Load Profile  With a limited supply of post-flight bearings available, initial test were performed on commercial bearings  with similar dimensions to the flight bearings. Balls and cages were removed from the commercial  bearings and 18 matched balls were added to make full complement test bearings, Le., no ball  separators. As shown in Table 1, S/N V6M002 had a maximum wear of 5.08 micro meters, which was  higher than the other flight bearing. Two commercial bearings were loaded to 26700 N and operated for  10 minutes at 72 rpm to produce wear similar to wear measured in Shuttle flight bearing after 20 to 30  missions, After this testing, the maximum wear on a test bearing (BF-003, Table 3) was found to be 4.45  micro meter. These damaged bearings were cleaned, re-lubricated with Braycote 601 EF and successfully  tested for 24 hours or 48 mission life at 60°C. The bearings successfully completed this testing and about  1.27 micrometer of additional wear was observed BF-003. During testing no evidence of degradation of  bearing performance was observed. Post-test inspection and metrology of the bearings showed moderate  additional wear in the bearings as shown in Table 3.  A photograph of a ball from BF-003 is shown in Figure 14. The photograph showed some banding and  blue discoloration due lubricant degradation. The test lubricant was found to be in good condition. It was  creamy white in color with some browr rnrl arm=,= ,-=~lfpd +ha p=rlll stage of lubricant degradation.  I  Figure 14. Ball from BF-003 after 48 Mission life test  26 1
Two additional 48 mission life tests were performed on previously flown flight bearings. The results of this  testing are shown in Table 4. Both tests were successfully completed. No indication of lubricant failure or  severe wear was observed. During the life testing, all bearings performed without anomalies and no  evidence of torque increase was observed with increasing test time. In addition, no rise in bearing  operating temperature was observed, which also indicated no gross degradation in bearing performance.  Post-test inspection of these bearings showed moderate additional wear (Table 4). No evidence of  lubricant failure, severe wear and or fatigue spalling was observed.  Test Serial Number  V6M014  V6L013  V6L001 Table 4. Wear for flight bearings after Shuttle Flights and after 48 missions of  Additional Life testing  Max wear before test Max wear 48 mission life test MSFC Life Test  (micro meter) (micro meter) Number  2.03 2.03 LT003  Wear debris build up .51 LT004  .38 Wear debris build UD LT004  After testing, the lubricant appeared to be in good condition. The grease in the bearings was still creamy  white with only a few areas of reddish brown discoloration (Figure 15). Balls from flight bearing showed  significant banding due to normal wear and possible lubricant degradation (Figure 16).  -  after 4imission cfe test Figure 16. A ball from flight bearing  V6L001 after 48 Mission of life tests  Results of this 48 mission life test showed that 3 previously flown flight bearings and 2 pre-damaged  commercial bearings successfully passed life testing for 24 hours or 48 missions at 60°C. Based on these  results, it was recommended that freshly re-lubricated, pre-flown body flap shaft bearings were  acceptable for 12 more flights on the Space Shuttle with safety factor of 4. When the average operation  time per mission was updated to 16 minutes per mission, the bearings were found to be acceptable for 22  missions at 60°C. This recommendation was based on the assumption that 60°C was the worst-case  condition for bearing lubricant life. Subsequent testing proved this assumption to be incorrect.  Life Testina of the Bodv FlaD Shaft Bearinas  The 48 mission life testing did not reproduce the black tribological coating on shaft test bearings, so  testing with partially lubricated bearings, different temperatures, speeds, and stop-start speed profiles  was continued in an attempt to produce the black tribological coating on the bearing wear surfaces, i.e.  SIN V6L009. The investigators were surprised to find the life of the bearings to be 10 to 20 hours rather  than the 66 hours originally required for the BF actuators. Shaft bearing life testing was redirected to  measure the life of the bearing and demonstrate that 12 more Shuttle missions could be successfully  accomplished.  In general, it was assumed the blackened balls were generated due to high local temperature, possibly  due to lubricant degradation, and\or starvation or from an external heat source during re-entry. The  objective of this testing was to generate blackened ball similar to those observed on BFA shaft bearing  262
SIN V6L009. A second objective of the testing was to determine the lubricant life of Braycote 601 grease  used in BFA shaft bearings.  Life Test Conditions:  1. Size 106 commercial 52-1 00 steel thrust bearings were life tested.  2. A shaft with bearings mounted on the ends was thrust loaded with a locking mechanical screw.  3. The drive shaft was rotated by an electrical motor driving a pulley mounted on the shaft.  4. The bearings were tested in air at room temperature.  5. The criteria for end of bearing life were the onset of a dropping preload, bearing temperature rise,  laboring of the drive motor and the onset of severe wear in the bearing.  The initial testing was performed at room temperature with continuous shaft rotation at 50 rpm. Tests  were run at several thrust load levels. The tests were allowed to run until lubricant failure was detected.  The results of testing are shown in Table 5.  Table 5. Body Shaft Bearing Life Test Results Using Commercially Equivalent Bearings  Bearing failures (lubricant failure) were observed much earlier than expected. These failures occurred  much sooner than in previous 60°C, 48 mission life tests where no failures were observed. The  mechanism continued to operate, but significant drops in axial load and bearing temperature increases  were observed as well as copious amounts of wear debris. Post-test microscopic examination of the  bearings showed two distinct wear modes.  1. Normal Wear Mode Characteristics  a. Race Appearance - Microscopic examination of the wear tracks in the races revealed a  smooth matte finish. In some cases, the wear track was bronze colored. The bearing  fabrication grinding marks were worn away.  b. Ball Appearance - The balls possess a shiny finish like a new ball. The shiny balls  surface are often coated with a thin smeared black film covering the balls or concentrated  in a wear ring pattern. The wear rings are produced when the rolls around a single axis.  2. Severe Wear Failure Mode (typical of failed bearings)  a. Race Appearance - Microscopic examination of the race. wear tracks showed very rough  surface. Wear scars form across the direction of ball motion. At higher loads and longer  bearing lives, radial wear scars develop between the wear tracks and the shoulder and  metal wear debris deposits on the bearing shoulder. Steel wear debris transfers from ball-  to-race and/or race-to-ball. As the bearing test time in the severe wear mode increased to  about 60 minutes, the transferred wear deposits turns black. The wear depth increased  from 3 micrometers for normal wear to about 80 micrometers for severe wear.  b. Ball Appearance - undulating rather than smooth ball surfaces were observed. As the test  time in the severe wear mode increased to about 60 minutes, the balls turned black.  263
Apparently, the black surface was formed when the worn balls heated up and oxidized  during the last few minutes of the test.  In general, failed bearings exhibited severe wear. A failed bearing is shown in Figure 17 and 18. The  onset of wear started when the lubricant between the ball and race was completely consumed or  degraded. Shear plastic deformation occurred between the race and ball steel to cause adhesive wear or  severe wear. Due to high friction and heat generation, the local ball temperatures rapidly increased and  caused oxidation and discoloration of bearing balls. In some case, the balls were highly discolored and  almost black. The test lubricant in the failed bearings was very dark in color with significant degradation  and metallic wear debris.  I  Figure 17. Failed Test Bearing BF012 Figure 18. Failed Test Bearing BF012  (disassembled)  Darkened balls that were produced in testing were not identical to the black ball from V6L009. Scanning  Electron Microscope examination of a failed test ball showed a texture surface. The surface of the test  bearings did not have a polished finished, but appears to have been smeared with transferred steel.  Some microspalling and surface cracking was observed. The flight bearing with the blackened balls (S/N  V6L009) was in fairly good shape. This flight bearing did not exhibit severe wear. Balls had smooth  surfaces and the raceway wear track was covered with smooth black oxide coating.  Life Testina at Elevated TemDerature  Due to these unexpected results of lower life at room temperature, life tests at elevated temperatures  were performed to confirm this trend. Tests were run at 60°C with 15569-N axial load at 50 rpm  continuous shaft rotation. One test was run at 70°C under the same conditions. The same bearing test rig  as previously described was used. The results are shown in Table 6 and Figure 20.  Table 6. Results of Continuous rotation testing at elevated temperature  264
NESC Bearing Testing  Effect of Temperature on Life  250000  50W  0  Room Temp, 50 rpm, Room Temp, 50 Room Temp, 50 140 F, 50 rpm Continous 165 F,80 rpm Continous  15569N rpm,20017N rpm,22241 N rotation, 15569N rotation, 15569N  Figure 20. The effect of temperature on lubricant life  The results of this testing indicated that temperature had a significant effect on bearing life. Increased  temperature yielded a significant increase in bearing life. The cause of this effect has not been  determined. One theory is the higher temperature afforded better lubrication either by a decrease in  apparent grease viscosity or by an increase in oil separation rate. This resulted in more oil available in  wear contact area thus extending bearing life.  STOP\START Testinq at Room TemDerature  The testing to determine the lubricant life was performed with continuous rotation. This differs from the 48  mission life tests that had been previously performed in several ways. In the 48 mission life testing, the  bearing ran at several different speeds and loads. Also, in actual BFA operation the actuator is operated  for short periods of time (several minutes) then sits stationary for extended periods (months). To evaluate  the effect of startbtop operation on the extension of bearing life, a series of stop\testing was performed  using the same bearing test rig as previously described.  For this testing the bearing rig was run for 30 minutes at 80 rpm shaft rotation and then held idle for 30  minutes. This cycle was continuously repeated until bearing failure occurred. For a baseline comparison  three additional tests were conducted with continuous rotation at 80 rpm. The results of this testing are  shown in Table 7 and Figure 21.  These results showed start\stop operation has a moderate effect on lubricant life. The average bearing  life for stopktart tests was 92500 revolutions which was about 30% greater than the average bearing life  for the continuous rotation testing, most probably because surface tension pulls lubricant into the wear  track while the bearings were stopped. These results also show that shaft speed had moderate beneficial  effect on bearing life most probable because more lubricant was squeezed out of the ball race contact at  lower speeds.  265
Table 7. Results of Startistop lubricant life testing  NESC BFA Bearing Testing  I  140 F, Mission Profile, 48 140 F, 50 rpm Continous Room Temp, 50 rpm, Room Temp, 80 rpm, Room Temp. 80 rpm,  Missions (no failures) rotation Continuous rotation Continous rotation stop\stati  Figure 21. Results of startbtop lubricant life testing  The start\stop testing at 80 rpm most closely simulated the actual BFA operation. The majority (92%)  cycles on the BFA are applied during ground operation under stop\start conditions. All of these cycles  occurred at 80 rpm with 15569-N axial load at room temperature. The remaining cycles occurred during  flight. The BFA was never operated under maximum load (22241-N load). This load occurred during  ascent when the actuator is in a lock position. The actuator was operated for several seconds in space to  test the actuator, but the remainder of cycles occurred during re-entry where temperature probably  266
Acknowledgments  The authors thank F. Hernandez, J. McManamen and J. Figert of Johnson Space Center; B. Heitzman  and L. Salvador of Boeing; P. Munafo, P. Hall. L. Moore, H. Gibson, M. Sharp, and S. Cat0 of Marshall  Space Flight Center; E. Devine of Swales Aerospace; E. Zaretsky and K. Street of Glenn Research  Center; J. York, D. Hill and S. Tollefson of Hamilton Sunstrand; and M. Sovinski of Goddard Space Flight  Center for their assistance. Without this team’s support, this task could not have been accomplished.  References  1.  2.  3.  4.  5.  6.  7.  8. L. Hughes, Hamilton Sundstrand; Destructive Analysis of Space Shuttle Body Flap Actuator  Blackened Ball Bearing, P/N 5902050, S.N V6L009, Memorandum Report 66852, February 17,2004  J. York, J. Sikes, L. Hughes, Hamilton Sundstrand; Overhaul Inspection Findings for Components  from Space Shuttle Body Flap Right-Hand Inboard Actuator Unit S/N 402, P/N 5003661A, Report  66442, Rev. A, January 24,2003  J. York, J. Sikes, L. Hughes, Hamilton Sundstrand; Overhaul Inspection Findings for Components  from Space Shuttle Body Flap Left-Hand Inboard Actuator Unit S/N 401, P/N 5001 41 B  Body Flap and Rudder Speed Brake Actuator Bearing Independent Technical Assessment Final  Report, NASA Engineering and Safety Center, NESC ITA 04-076-1  S. N. Cato, Marshall Space Flight Center; Orbiter Body Flap Actuator Bearings  K. Street and M. Sovinski; Analysis of Black Bearing Balls from a Space Shuttle Body Flap Actuator,  Proceedings of World Tribology Congress Ill, Washington, D. C. September 12-16,2005  P. Herrera-Fierro, M. Masuko, W. Jones, S. Pepper, Glenn Research Lab.; XPS Analysis of 440C  Steel Surfaces Lubricated with Perfluoropolyethers Under Sliding Conditions in High Vacuum, NASA  Tech. Memo. 106548, April 1994  W. Jones, Glenn Research Lab and M. Jansen, Univ. of Toledo; Lubrication for Space Applications,  NASNCR 2005-21 3424, January 2005  268
Bearing Development for a Rocket Engine Gimbal  Christian Neugebauet, Manfred Falkner*, Ludwig Supper* and Gerhard Traxler*  Abstract  The bearings for a gimbal of a cryogenic upper-stage rocket engine are highly loaded, they are exposed to  corrosive environment, and they have to cope with a wide temperature range down to cryogenic  temperatures. A tailored single-row full-complement needle roller bearing design integrated by press fit  mount technology was selected for this specific application. This paper describes the design  considerations, the analysis approach, and the development test results of these bearings.  Introduction  Austrian Aerospace has the privilege to develop the gimbal for the next generation upper-stage engine of  the ARIANE 5 Launcher family, the VlNCl engine. One of the key components of the gimbal are the  bearings which  -  -  -  - are highly loaded by the engine operating loads and by inertial loads,  are limited in space and mass due to stringent mass and envelope requirements,  must tolerate considerable misalignments of the axis due to elastic deformation of the gimbal under  mechanical load, and  have to cope with harsh environmental loads and cryogenic temperatures.  The chosen bearing is a tailored needle roller bearing with specially crowned needles. To transmit the high  loads, the bearing pitch circle diameter should be as large as possible. This leads to a design with a  bearing integrated by press fit mount technology to allow for an undivided bearing support to find a space  and mass optimized assembly design.  The design and dimensioning of the press fits was driven by the following constraints:  -  -  -  -  - Maintenance of proper fit under any thermal load-case to prevent loosening of the bearing rings in the  support when experiencing thermal gradients,  The reduction of the bearing’s radial clearance during integration caused by the press fits,  Elastic deformation of the race along the bearing axis due to the unequal stiffness distribution of the  bearing housing. Such deformations may not disturb the radial clearance of the bearing.  Roundness deviations of the race due to radial elastic deformation caused by the unequal stiffness  distribution of the bearing housing.  The unequal stiffness distribution of the bearing housing and the thin sectioned design also causes  roundness deviations caused by the manufacturing process of the housing that sums up with radial  elastic deformations due to the press fit.  The design must allow the introduction of considerable axial integration forces during bearing  insertion. -  The development test results confirmed the chosen design.  * Austrian Aerospace GmbH, Vienna, Austria  Proceedings of the 3dh Aerospace Mechanisms Symposium, Langley Research Center, May 17- 19,2005  269
Description of the Mechanism  Bearing type  Material of rings and rollers  Lubricant  Supplier of the bearing The main functions of the gimbal are to fix the engine in its defined position, to transfer the thrust and all  inertial forces from the engine to the stage and to allow the gimbal operation. The gimbal consists mainly  of an engine-side bracket, the gimbal cross, and the stage-side bracket, connected by two pairs of  bearings. The distance between the gimbal interface plates amounts to 150 mm. Four single-row needle  roller bearings allow gimbal motion about two axes. The development of these bearings is described in  this paper.  Single row needle roller bearing  Cronidur 30  Sputtered Lead by ESTL, UK  FAG Kugelfischer AG, Germany A  i  Figure 1. CAD model and development model of the Gimbal, with uncovered bearings  Bearing Type, Layout and Design  Table 1 presents the main parameters of the bearings described in this paper.  Table 1. Bearing Parameters  Bearina TvDe  At an early stage of the development, the decision for rolling bearings was made due to the low friction  torque and the low wear of rolling bearings. The decision for a needle roller bearing was driven by the load  capability of the bearing at a given envelope restriction. This lead to a one-row full-complement needle  roller bearing design.  The race of the outer ring is equipped with borders to position the needle rollers in the axial direction. As  no lateral force transmission by the bearing is required, the races of the inner ring are not equipped with  borders.  270