ASTM G182-2013(2018) Standard Test Method for Determination of the Breakaway Friction Characteristics of Rolling Element Bearings.pdf

1、Designation: G182 13 (Reapproved 2018)Standard Test Method forDetermination of the Breakaway Friction Characteristics ofRolling Element Bearings1This standard is issued under the fixed designation G182; the number immediately following the designation indicates the year oforiginal adoption or, in th

2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is an extension of Test Method G164and uses an inclined plane and a p

3、aperclip rider to detect thepresence or absence of lubricants on the surfaces of flexiblewebs. A study to identify free spinning or low rolling frictionbearings indicated that the paperclip friction test could be usedfor rolling friction by simply replacing the paperclip with arolling element bearin

4、g on an axle. The angle of the inclinedplane at initiation of rolling is the breakaway angle. This testmethod can be used to measure the angle at breakaway of smalldiameter (up to 100 mm outside diameter) rolling elementbearings. The bearings that have been tested in the develop-ment of this method

5、are conventional ball bearings withdifferent separators, seals, and different conditions of lubrica-tion (none, oil, greases, and so forth), but there is no technicalreason why this test method would not work with bearings ofother design, including plain bearings. Rolling element bear-ings like any

6、sliding system can have friction characteristics atbreakaway that are different than rolling continuously.As is thecase with most inclined plane friction tests, the test onlyproduces the friction characteristic at the onset of measurablerolling, using the angle () when measurable rolling com-mences.

7、 The objective of this test is an assessment of break-away rolling friction characteristics to assist machine designersin the selection of rolling element bearings for instrumentpivots and the like where breakaway friction is a concern.1.2 The values stated in SI units are to be regarded asstandard.

8、 No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-m

9、ine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendation

10、s issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2G40 Terminology Relating to Wear and ErosionG117 Guide for Calculating and Reporting Measures ofPrecision Using Data from Interlaboratory Wear or Ero-sion Tests (Withdrawn 2

11、016)3G143 Test Method for Measurement of Web/Roller FrictionCharacteristicsG164 Test Method for Determination of Surface Lubricationon Flexible Webs3. Terminology3.1 Definitions Relating to Wear and Erosion (taken fromTerminology G40):3.1.1 coeffcient of friction, in tribology, the dimension-less ra

12、tio of the friction force (F) between two bodies to thenormal force (N) pressing these bodies together.3.1.2 friction forcethe resisting force tangential to theinterface between two bodies when, under the action ofexternal force, one body moves or tends to move relative to theother.3.1.3 kinetic coe

13、ffcient of frictionthe coefficient of fric-tion under conditions of macroscopic relative motion betweentwo bodies.3.1.4 lubricantany substance interposed between two sur-faces for the purpose of reducing the friction and wear betweenthem.3.2 Definitions Not Covered by Terminology G40:3.2.1 breakaway

14、 coeffcient of rolling frictionthe force inthe direction of rolling (F) required to produce rolling of a1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.50 on Friction.Current edition approved June 1, 2018. Publ

15、ished July 2018. Originally approvedin 2006. Last previous edition approved in 2013 as G182 13. DOI: 10.1520/G0182-13R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refe

16、r to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed i

17、n accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1shape that is capable of

18、rolling on a surface, divided by thenormal force (N) on the rolling shape: rolling 5FN(1)3.2.2 inclined planea surface that can be raised at an angleto produce motion of an object on the plane.3.2.3 plain bearingsa cylindrical shape used to support arotating shaft.3.2.4 rolling element bearingballs

19、or rollers in racewaysthat support a shaft and allow rotation of the shaft or bearingouter race (OD).4. Summary of Test Method4.1 This test method can be used to measure the breakawayrolling friction characteristics of rolling element bearings.4.2 Small rolling element bearings (less than 100 mmouts

20、ide diameter) are affixed to a balanced rider and placed onan incline. The rider is designed so that it becomes the axleabout which the bearing rotates. The inclined plane is raised(by hand or mechanism) until the outer race (OD) of thebearing starts to roll on the inclined plane. The inclined plane

21、surface is covered with a plasticized PVC tape to increase thestatic friction between the outside surface of the bearing andinclined plane. The test will not yield rolling friction charac-teristics if the bearing slides rather than rolls on the inclinedplane.4.3 The rolling friction characteristics

22、measured by this testare the net result of the bearing design, materials and state oflubrication. This this test could also be used to evaluate bearingdesigns and bearing greases.5. Significance and Use5.1 This test is a simple, effective way of determining theability of bearings to roll freely. Mos

23、t bearing manufacturersdo not supply information on the breakaway friction coefficientof their products and if this is a design factor, users often buycandidate bearings and try them until they find one that appearsto operate freer than the others. This test allows quantificationof the breakaway fri

24、ction characteristics of bearings. This testassesses the friction of a bearing as a tribosystem whichincludes its construction and lubrication. It has shown tocorrelate with use. If a bearing has a low breakaway angle inthis test, its breakaway friction will be lower in service than thesame size bea

25、rings that displayed a higher breakaway angle inthis test.5.2 Breakaway friction of bearings is important in instru-ments where forces are light and the bearings are used as pivotsrather than for continued rotation. Low friction is oftenimperative for proper device operation.5.3 Bearings with low br

26、eakaway friction are often soughtfor web handling rollers. Many rollers are driven only bytangential web contact and slippage can often damage the web.Low friction bearings are required.5.4 This test is useful for screening bearings for anyapplications where breakaway friction is a design concern.NO

27、TE 1User must determine weight and center of gravity. All components to be made from brass or steel.FIG. 1 Suggested Balancing ArmG182 13 (2018)26. Apparatus6.1 Bearing AxleThe test bearing is clamped between twotapered plugs assembled on the threaded-rod rider shown inFig. 1. The tapered plugs are

28、tightened such that the inner raceof the bearing is fixed to and centered on the horizontal portionof the threaded rod.6.2 WeightsThe normal force of the bearing on the in-clined plane is produced by the cumulative mass of the bearingand the rider assembly that holds the bearing. The weight of theri

29、der (without the bearing) shall be 90 to 100 g and theassembly should weigh between 100 and 130 g. The assembledtest bearing and rider should weigh the same for each testbearing. Weights in the form of bushings or washers can beaffixed to the axle portion of the rider to make all testassemblies have

30、 the same weight (65 g). Weights must beadded in pairs with equal amounts on each side of the rider.6.3 Inclined PlaneThe inclined plane should be from 20to 30 mm wide, a minimum of 250 mm long, be a rigid material(hard plastic, metal, etc.) and be capable of being raised on apivot and locked in pla

31、ce at the rider breakaway angle. Theinclined plane should be high enough to allow unobstructedrolling of the rider down the plane (Fig. 2).6.4 Rolling SurfaceThe inclined plane should be coveredby a single layer of 127/152 m inch-thick plasticized PVCtape (black electrical tape) with the pressure se

32、nsitive adhesive(PSA) surface adhered to the plane. The tape must be widerthan the test bearing by at least 2 mm on each side. The purposeof the tape is to increase the friction between the outer race andthe inclined plane. Tests with Test Method G143 capstanfriction test identified this material as

33、 having high friction( 0.5) against hardened steel. If the outer race slides on theinclined plane before the bearing rotates, the result will besliding friction, not rolling friction. Fiduciary marks can beused to verify that the bearing does not slide.6.5 Angle MeasurementThe test metric is the inc

34、linationof the inclined plane when rider motion occurs. This angle canbe measured by a protractor or by calibration of a gage on thedevice. Some inclined planes use an electronic encoder to yieldthe angle. The least count on the angle measuring device shallbe 1 degree.7. Test Procedure7.1 Sample Pre

35、parationBearings are to be tested in thecondition that they will be used. Rolling friction is affected bythe bearing design (separators, clearances, materials, and soforth) and lubrication. The outside diameter should bedegreased with a solvent such as acetone in such a way that thecleaning solvent

36、does not get into the lubricant or rollingelements. A wipe with an acetone soaked cloth is usuallyadequate. A fresh strip of black electrical tape should beapplied to the rolling surface on the inclined plane using cottongloves to prevent surface contamination. The tape should notbe touched or conta

37、minated in any way.7.2 Assemble the cleaned bearing on the rider axle makingsure that it freely rotates about the axle (partial manualrevolution), to ensure proper seating of the tapered cones.7.3 Test ConditionsConduct tests with relative humiditybetween 35 and 75 % and at a temperature of 20 6 3C.

38、Condition samples for 24 h in the test atmosphere prior totesting.7.4 Conducting the TestLevel the test apparatus to within1/50 cm in longitudinal and transverse directions and placethe rider on the tape-covered plane (Fig. 2). Raise the sampleplane until the bearing just starts to roll. Fiduciary m

39、arks on theFIG. 2 Schematic of Test RigG182 13 (2018)3plane and bearing outside diameter can be used to verifyrolling. Motion of the sample plane should be slow and not toexceed 1/s and be steady. Record this angle.7.4.1 Repeat the procedure twice more and calculate theaverage of the three angle det

40、erminations.7.4.2 Do not spin the bearing races before or during testingunless this is the way that they will be used in service. Test theway bearings will be used in service. Usually this test will beused to compare the same nominal size bearings for breakawayfriction, so bearing mass differences a

41、re not a concern. Appro-priate weights (see Note 1) can be added to the balance arm toproduce equal rider mass for testing bearings with weightdifferences.NOTE 1Add washers at the back of the cones that clamp the innerrace.8. Report8.1 Test DataThe following values shall be recorded:8.1.1 The name a

42、nd number of the test bearing,8.1.2 The description and condition of the test counterface,8.1.3 The average breakaway of rolling friction (r)ofthetest couple,8.1.4 The number of test replicates,8.1.5 The standard deviation of the test replicates, and8.1.6 The temperature and relative humidity of the

43、 testenvironment.8.2 Interpretation of ResultsThe test is intended to iden-tify free-rolling bearings from sticky bearings. High coeffi-cients of variation can be an indicator of a sticky bearing.9. Precision and Bias9.1 The test variability in interlaboratory tests on seven ballbearings is illustra

44、ted in Fig. 3.9.1.1 The within-laboratory coefficient of variation was inthe range of 9.21 to 22.2 %. The average for five laboratorieswas 14 %. The average 95 % confidence limit was 0.03. Thebetween-laboratory variability (COV) ranged from 22.9 to75 %. The average was 46 %. The average 95 % confide

45、ncelimit was 0.1.9.2 BiasThere is no absolute value of friction coefficient.It is a product of a tribosystem. Therefore, the magnitude of thevalue cannot be determined. Some of the factors that can affectreproducibility and repeatability problems are:9.2.1 Contamination of test surfaces,9.2.2 Irregu

46、lar (jerky) motion in raising the inclined plane,9.2.3 Non-smooth counterface,9.2.4 Imbalance of the bearing holder, and9.2.5 Significant differences in bearing size (see Note 2)(when comparing bearings).NOTE 2The bearing assembly in interlaboratory tests varied in weightbetween 100 and 130 g. These

47、 differences were ignored to keep the testsimple. Future interlaboratory test will keep assembly weight the same fora group of test bearings.10. Keywords10.1 coefficient of rolling friction; friction testing; rolling;rolling frictionFIG. 3 Within-Lab ResultsG182 13 (2018)4ASTM International takes no

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