1、Designation: G 182 06Standard Test Method forDetermination of the Breakaway Friction Characteristics ofRolling Element Bearings1This standard is issued under the fixed designation G 182; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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 is an extension of Test Method G 164and uses an inclined plane and a paperclip rider
3、 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 bearing on an axle.
4、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 are convention
5、al 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 sliding system
6、 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 (u) when measurable rolling com-mences. The objectiv
7、e 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. No other uni
8、ts 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 and health practices and determine the applica-bility of regu
9、latory limitations prior to use.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 TestsG 143 Test Method for Measurement of Web/Roller Fric-tion Charact
10、eristicsG 164 Test Method for Determination of Surface Lubrica-tion on Flexible Webs3. Terminology3.1 Definitions Relating to Wear and Erosion (taken fromTerminology G40):3.1.1 coeffcient of friction, in tribology, the dimension-less ratio of the friction force (F) between two bodies to thenormal fo
11、rce (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 coeffcient of frictionthe coefficient of fric-tion under conditions
12、 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 coeffcient of rolling frictionthe force inthe direction of roll
13、ing (F) required to produce rolling of arevolute shape on a surface, divided by the normal force (N) onthe revolute shape: rolling 5FN(1)1This 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 ed
14、ition approved May 1, 2006. Published May 2006.2For 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 Document Summary page onthe ASTM website.1Copyright AST
15、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2 inclined planea surface that can be raised at anangle to produce motion of an object on the plane.3.2.3 plain bearingsa cylindrical shape used to support arotating shaft.3.2.4 rollingmotion of
16、revolute shape (ball, wheel, roller,and so forth) in a specific direction, on a surface such that thereis no relative slip in all or part of the area of contact.3.2.5 rolling element bearingballs or rollers in racewaysthat support a shaft and allow rotation of the shaft or bearingouter race (OD).4.
17、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 mmoutside diameter) are affixed to a balanced rider and placed onan incline. The rider is designed so that it
18、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 planesurface is covered with a plasticized PVC tape to increase thestatic friction between the outside surfac
19、e 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 measured by this testare the net result of the bearing design, materials and state oflubrication. Thus t
20、his test could also be used to evaluatebearing designs and bearing greases.5. Significance and Use5.1 This test is a simple, effective way of determining theability of bearings to roll freely. Most bearing manufacturersdo not supply information on the breakaway friction coefficientof their products
21、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 friction characteristics of bearings. This testassesses the friction of a bearing as a tribosystem whichinc
22、ludes 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 bearings that displayed a higher breakaway angle inthis test.5.2 Breakaway friction of bearings is importan
23、t 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 breakaway friction are often soughtfor web handling rollers. Many rollers are driven only bytangential web
24、 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.6. Apparatus6.1 Bearing AxleThe test bearing is clamped between twotapered plugs assembled on the threaded
25、-rod rider shown inFig. 1. The tapered plugs are tightened such that the inner raceNOTEUser must determine weight and center of gravity. All components to be made from brass or steel.FIG. 1 Suggested Balancing ArmG182062of the bearing is fixed to and centered on the horizontal portionof the threaded
26、 rod.6.2 WeightsThe normal force of the bearing on theinclined plane is produced by the cumulative mass of thebearing and the rider assembly that holds the bearing. Theweight of the rider (without the bearing) shall be 90 to 100 gand the assembly should weigh between 100 and 130 g. Theassembled test
27、 bearing and rider should weigh the same foreach test bearing. Weights in the form of bushings or washerscan be affixed to the axle portion of the rider to make all testassemblies have the same weight (65 g). Weights must beadded in pairs with equal amounts on each side of the rider.6.3 Inclined Pla
28、neThe 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 place at the rider breakaway angle. Theinclined plane should be high enough to allow unobstructedrolling of the rider d
29、own 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 sensitive adhesive(PSA) surface adhered to the plane. The tape must be widerthan the test bearing by at least 2 mm on
30、each side. The purposeof the tape is to increase the friction between the outer race andthe inclined plane. Tests with Test Method G 143 capstanfriction test identified this material as having high friction( 0.5) against hardened steel. If the outer race slides on theinclined plane before the bearin
31、g 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 inclinationof the inclined plane when rider motion occurs. This angle canbe measured by a protractor or by calibration
32、 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 PreparationBearings are to be tested in thecondition that they will be used. Rolling friction is affected bythe bearin
33、g design (separators, clearances, materials, and soforth) and lubrication. The outside diameter should be de-greased with a solvent such as acetone in such a way that thecleaning solvent does not get into the lubricant or rollingelements. A wipe with an acetone soaked cloth is usuallyadequate. A fre
34、sh 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 contaminated in any way.7.2 Assemble the cleaned bearing on the rider axle makingsure that it freely rotates about the
35、 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.Condition samples for 24 h in the test atmosphere prior totesting.7.4 Conducting the TestLevel the test apparatus
36、 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 marks on theplane and bearing outside diameter can be used to verifyrolling. Motion of the sample plane should be
37、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 determinations.FIG. 2 Schematic of Test RigG1820637.4.2 Do not spin the bearing races before or during testingunless this is the way that they will be used in
38、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 are not a concern. Appro-priate weights (see Note 1) can be added to the balance arm toproduce equal rider mass for testin
39、g 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 and number of the test bearing,8.1.2 The description and condition of the test counterface,8.1.3 The average breakaway of
40、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 testenvironment.8.2 Interpretation of ResultsThe test is intended to iden-tify free-rolling bearings from sticky bearing
41、s. 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 illustrated in Fig. 3. The conditional data areanalyzed per G117in Appendix X1.9.1.1 The within-laboratory coefficient of variati
42、on 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 % confidencelimit was 0.1.9.2 BiasThere is no absolute value of friction
43、coefficient.It is a product of a tribosystem. Therefore, the value can haveno bias. Some of the factors that can affect reproducibility andrepeatability problems are:9.2.1 Contamination of test surfaces,9.2.2 Irregular (jerky) motion in raising the inclined plane,9.2.3 Non-smooth counterface,9.2.4 I
44、mbalance 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 differences were ignored to keep the testsimple. Future interlaboratory test will ke
45、ep assembly weight the same fora group of test bearings.10. Keywords10.1 coefficient of rolling friction; friction testing; rolling;rolling frictionFIG. 3 Within-Lab ResultsG182064ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item m
46、entionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committ
47、ee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meet
48、ing of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, P
49、O Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).G182065
