1、Designation: F 2661 07Standard Test Method forDetermining the Tribological Behavior and the RelativeLifetime of a Fluid Lubricant using the Spiral OrbitTribometer1This standard is issued under the fixed designation F 2661; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the quantitative determinationof the fric
3、tion coefficient and the lifetime of oils and greases,when tested on a standard specimen under specified conditionsof preparation, speed, Hertzian stress, materials, temperature,and atmosphere, by means of the Spiral Orbit Tribometer(SOT). This test method is intended primarily as an evaluationof th
4、e lifetimes of fluid lubricants under vacuum and ambientconditions.1.2 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard
5、 toestablish appropriate safety and health practices and todetermine the applicability of regulatory limitations prior touse.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterF22 Test Method for Hydrophobic Surface Films by theWater-Break TestF 2215 Specification for B
6、alls, Bearings, Ferrous and Non-ferrous for Use in Bearings, Valves, and Bearing Applica-tionsG 115 Guide for Measuring and Reporting Friction Coeffi-cients2.2 Anti Friction Bearing Manufacturers Association Stan-dards3ANSI ABMA ISO 3290 (AFBMA Standard 10 Balls)3. Terminology3.1 Definitions:3.1.1 c
7、oeffcient of frictionthe dimensionless ratio of thefriction force between two bodies to the normal force pressingthese bodies together.3.1.2 fixed platestationary, horizontal flat plate, typicallythrough which a force (the “load”) is applied to the ball.3.1.3 friction coeffcient limitmaximum value t
8、hat thefriction coefficient is permitted to attain.3.1.4 guide platephysical element that deflects the ball toits original orbit radius.3.1.5 lubricant total amount mass of lubricant depositedon the entire ball surface at the beginning of the test.3.1.6 normalized lifetimenumber of ball orbits perfo
9、rmeduntil the friction coefficient limit is reached divided by thelubricant total amount initially deposited on the ball.3.1.7 rotary plateflat plate rotating at a constant rateselected for the test.3.1.8 scrub zoneRegion of the balls orbit in which theball is in contact with the guide plate.3.1.9 s
10、piral orbittrack traced by the ball on the fixed androtating plates of the Spiral Orbit Tribometer. The track has aspiral shape.4. Summary of Test Method4.1 Alubricated ball is clamped between two parallel plates.One of the plates rotates up to 210 rpm, causing the ball to rollin a near-circular orb
11、it, but is actually an opening spiral. Aclamping force, the “load”, provides a chosen mean Hertzstress (typically 1.5 GPa). The system is targeted to operate inthe boundary lubrication regime due to the combination of thehigh load, the moderate speed, and the small amount oflubricant (approximately
12、50 g). The ball rolls and pivots in aspiral orbit and is maintained in the orbit by the guide plate.The ball slides on the rotating plate when it contacts the guideplate. The measured force exerted by the ball on the guide plateis used to determine the friction coefficient. The tribometerruns until
13、the coefficient of friction rises to values much largerthan the initial, steady value. At this point the initial charge oflubricant has been depleted by tribodegradation and the system1This test method is under the jurisdiction of ASTM CommitteeF34 on RollingElement Bearings and is the direct respon
14、sibility of Subcommittee F34.02 onTribology.Current edition approved June 1, 2007. Published July 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards
15、 Document Summary page onthe ASTM website.3Available from American Bearing Manufacturers Association (ABMA), 8221Old Courthouse Road, Suite 207 Vienna, Virginia 22182.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.is running virtual
16、ly unlubricated. The normalized lifetime isobtained from the number of spiral orbits completed beforereaching the chosen friction coefficient limit divided by thetotal lubricant mass on the ball at the beginning of the test. Aminimum of four tests per lubricant and test condition shall beperformed.
17、Lubricants can be compared by calculating theiraverage normalized lifetimes for a given set of test conditions.5. Significance and Use5.1 Relevance of the Spiral Orbit Tribometer (SOT)TheSOT was designed to evaluate the relative degradation rates ofliquid lubricants in a contact environment similar
18、to that in anangular contact bearing operating in the boundary lubricationregime. It functions as a screening device to quickly select thelubricants, evaluate the ability of various components of alubricant (base oil, thickener, or additive) to lubricate a contactin rolling, pivoting, and sliding co
19、nditions simultaneously, andstudy their chemical decomposition if necessary. The SOTprovides a means to study the tribological behavior of oils andgreases during operation, while they undergo changes as afunction of typical parameters encountered in the lubricationfield (temperature, environment, ma
20、terials used, load applied,and speed). Test conclusion is defined to be when a frictioncoefficient limit (typically an increase of 0.1 above the steadystate value) is surpassed. Normalized lubricant lifetime is thendefined as the number of orbits completed divided by the initialamount of lubricant u
21、sed (in g). The SOT was initiallydeveloped to evaluate lubricants for space applications, but isalso relevant for conventional environments. Some results invacuum are presented (Fig. 1). At this time, no data for tests inambient conditions have been published (see Fig. 2). The userof this test metho
22、d should determine to their own satisfactionwhether results of this test procedure correlate with fieldperformance or other bench test procedures.6. Apparatus6.1 The Spiral Orbit Tribometer (SOT)See Fig. 3.6.1.1 General descriptionFig. 3 shows a schematic draw-ing of a typical SOT. The system consis
23、ts of a lubricated ballrolling and pivoting between a fixed plate and a rotary plate.The load is applied through the fixed plate. The track is a spiraland the ball is returned to its original orbit radius by contactingthe guide plate, which forces the ball to return to its originalradius each orbit.
24、 The friction coefficient is determined by themeasuring the force on the guide plate when the ball contactsthe guide plate. A piezoelectric force transducer is attached tothe guide plate. This force, divided by twice the normal load,is the friction coefficient.6.1.2 Motor driveA variable speed motor
25、, capable ofconstant speed, is required. Rotating plate speeds are typicallyin the range 1 to 210 rpm (0.10 to 22 rad.s1). The effectivestiffness of the axis shall be at least 1.8 E +05 Newton/meteraxial in the load direction, 3.6 E +08 Newton/meter radial and1.13 E +05 Newton-meter/Radian moment. T
26、he TIR of themotor shaft shall be 0.0254 millimeters maximum.6.1.3 Fixed load plateThe load plate shall have an axialstiffness of at least 1.8 E +08 Newton/meter in the loaddirection. The effective radial stiffness of the plate axis shall beat least1.8 E+08 Newton/meter and the moment stiffness shal
27、lbe at least 1.13 E +05 Newton-meter/Radian.6.1.4 Orbit counterThe SOT shall be equipped with arevolution counter or its equivalent that will record the numberof ball orbits. The tribometer would preferably have the abilityto shut off after a pre-selected number of orbits or frictioncoefficient has
28、been reached.6.1.5 Applied loadThe fixed plate is attached to a systemto apply the load, up to 222.5 N (50 lb.), providing the desiredHertzian stress, typically 1.5 GPa.6.1.6 The instruments and gauges:6.1.6.1 Friction forceThe friction coefficient is deter-mined by measuring the force on the guide
29、plate while the ballcontacts the guide plate. This force is measured using apiezoelectric force transducer and a charge amplifier. Thefriction force and the coefficient of friction can then bePepper, S.V., Kingsbury, E.P., “Spiral Orbit Tribometry Part II: Evaluation of Three Liquid Lubricants in Va
30、cuum”, Tribo. Trans., V 46, 1, pp 65-69, 2003FIG. 1 Relative lifetimes of three typical space lubricants at 23C in vacuum on 52100 steelF2661072obtained as explained in Section 11. The load cell shall belinear to within 2 % across the entire temperature range of thetest.6.1.6.2 EnvironmentThe SOT op
31、erates in either one at-mosphere air, under a cover gas, or vacuum. When operatingunder vacuum or ultrahigh vacuum, a cold cathode pressuregauge attached to the chamber monitors the pressure. A hotcathode gauge should be avoided since electrons from thefilament could alter lubricant chemistry. It is
32、 the responsibilityof the user to determine the chemical purity of the environmentand gas to establish the contribution to tribochemistry.6.1.6.3 Measurement of the temperatureWhen a con-trolled temperature is required, the temperature is monitoredusing a thermocouple (for example, K-type) attached
33、to thestationary disk during the test.Bazinet, D.G., Espinosa, M.A., Loewenthal, S.H., Gschwender, L., Jones, W.R., Jr., Predmore, R.E., “Life of Scanner Bearings with Four Space Liquid Lubricants”, Proc.37thAerospace Mech. Symp., Johnson Space Center, May 19-21, 2004FIG. 2 Comparison between full s
34、cale bearing tests* and SOT data at 23C on 440C steel.FIG. 3 Detail of the Spiral Orbit TribometerF26610737. Reagents and Materials7.1 Balls, plates, guide plates. Typical instrument bearingmaterials may be of 440C material, but other materials may beused to simulate the bearing application.7.1.1 Te
35、st ballsTest balls shall be 12.7 mm (0.5 inch)diameter, grade 25 or better, made with 440C stainless steel.Their recommended Rockwell hardness shall be 58 to 62. SeeSpecification F 2215 or ANSI ABMA ISO 3290 (AFBMAStandard 10) for ball specification reference. Other materialsmay be used to simulate
36、specific application chemistry.7.1.2 Plates, Guide platesThe fixed plate and the rotaryplate are disks of 50.8 mm (2 inch) in diameter, may be madewith 440C stainless steel, or any desired material. Surfaceroughness of 0.05 mm average roughness or less is recom-mended. The guide plates are small cyl
37、inders 12.7 mm (0.5inch in diameter), with a polished surface of 0.05 mm averageroughness or less (recommended). The recommended Rock-well hardness for 440C shall be 58 to 62. Stationary and rotaryplates should be made with the same material. Any bearingmaterial can be used, depending on the applica
38、tion beingsimulated. The recommended values should be used unlessdifferences are required to simulate a specific application.7.1.3 Care must be taken in surface preparation and han-dling to avoid surface damage or contamination after cleaningthat alters the material. Typical cleaning methods may be
39、usedwhen the results will pass anTest Method F22standard test forwetability and do not damage the materials or adversely alterthe sample surfaces. A wettability test using the intendedlubricant to evaluate the ball and plate cleaning method isrecommended.7.1.4 Reagent grade chemicals shall be used p
40、er TestMethod F22 section 8.1. It is the users responsibility toprevent contamination or adulteration of the lubricant samples,and prevent materials used to clean or lubricate from harmingthe samples.8. Hazards8.1 Use of solventsOperator will refer to the safety datasheet of all the solvents used an
41、d will take appropriateprecautions.8.2 Use of ultrasonic cleaning systems (if applicable)Operator will refer to the instruction manual of the ultrasonicbath before use.8.3 Use of ultra violet (U.V.)/ozone cleaning system (ifapplicable)Operator will refer to the instruction manual ofthe U.V./ozone cl
42、eaning system before use. Special care will betaken to check the compatibility of the materials used to a U.V.and ozone exposure.8.4 Ultrahigh vacuum chamber (if applicable)Thevacuum chamber will be operated with appropriate copper orelastomer seals to reach ultrahigh vacuum, and will not beopened u
43、ntil the inside of the chamber has reached atmosphericpressure.9. Sampling, Test Specimens, and Test Units9.1 Test specimens Specimens (plates, balls, guide plates)will be kept for further analysis, if required.9.2 Test unitsOnly SI units will be used.10. Procedure10.1 Cleaning of the parts and tool
44、s may be any method thatsimulates the application. It is recommended that the results ofcleaning procedures are tested using a water break free testsuch as Test Method F22 using reagent grade water perSpecification D 1193, or a wettability test using the intendedoil. Since many variations of cleanin
45、g methods exist and theirresults may have a strong effect on the results, it is the usersresponsibility to determine the effectiveness and safety of thecleaning methods. The details of the cleaning methods shalldescribed in the test report.10.2 Lubrication of the ballsLubrication of the test system
46、is to the ball only. Theobjective is to lubricate the balls with a small and controlledamount of lubricant. The target amount is as close as possibleto 50 +/ 2 g for a 12.7 mm diameter ball.10.2.1 Lubrication of the balls with oil10.2.1.1 Preparation of a dilute solution of oil:(1) Choose a solvent
47、suitable for the oil to be tested. Theuser must determine that the solvent does not harm the samplesurface or alter the lubricant.(2) Weigh a clean, dry and empty bottle.(3) Put a small drop of oil within the bottle.(4) Note the mass of oil (moil) in milligrams.(5) Add a volume of solvent in the bot
48、tle to obtain theproportion of one milliliter of solvent per one milligram of oil.(6) Close the bottle and shake it to create an homogeneoussolution.It is the responsibility of the user to determine the type ofsolvent used. Some solvents may not produce a homogeneoussolution and can have an adverse
49、effect on the results. Caremust be taken to produce a final lubricant film that isunadulterated on the ball.10.2.1.2 Lubrication of the ball:(1) Weigh a dry, clean ball with a micro-balance to 62 g.(2) Fill a micro-syringe with the dilute oil solution.(3) Attach the ball to a handling tool that spins the ball andstart the ball spinning.(4) Put fifty microliters, drop by drop, of the dilute solutionon the surface of the spinning ball.(5) Wait at least five minutes or until the weight of thesample is stable to allow the solvent to evaporate.(6)
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