1、Designation: G182 06G182 13Standard 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 the case of r
2、evision, 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 G164 and uses an inclined plane and a paperclip r
3、ider to detect the presenceor absence of lubricants on the surfaces of flexible webs.Astudy to identify free spinning or low rolling friction bearings indicatedthat the paperclip friction test could be used for rolling friction by simply replacing the paperclip with a rolling element bearingon an ax
4、le. The angle of the inclined plane at initiation of rolling is the breakaway angle. This test method can be used to measurethe angle at breakaway of small diameter (up to 100 mm outside diameter) rolling element bearings. The bearings that have beentested in the development of this method are conve
5、ntional ball bearings with different separators, seals, and different conditionsof lubrication (none, oil, greases, and so forth), but there is no technical reason why this test method would not work with bearingsof other design, including plain bearings. Rolling element bearings like any sliding sy
6、stem can have friction characteristics atbreakaway that are different than rolling continuously.As is the case with most inclined plane friction tests, the test only producesthe friction characteristic at the onset of measurable rolling, using the angle () when measurable rolling commences.The objec
7、tiveof this test is an assessment of breakaway rolling friction characteristics to assist machine designers in the selection of rollingelement bearings for instrument pivots and the like where breakaway friction is a concern.1.2 The values stated in SI units are to be regarded as standard. No other
8、units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of r
9、egulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2G40 Terminology Relating to Wear and ErosionG117 Guide for Calculating and Reporting Measures of Precision Using Data from Interlaboratory Wear or Erosion TestsG143 Test Method for Measurement of Web/Roller Friction Charact
10、eristicsG164 Test Method for Determination of Surface Lubrication on Flexible Webs3. Terminology3.1 Definitions Relating to Wear and Erosion (taken from Terminology G40):3.1.1 coeffcient of friction, in tribology, the dimensionless ratio of the friction force (F) between two bodies to the normalforc
11、e (N) pressing these bodies together.3.1.2 friction forcethe resisting force tangential to the interface between two bodies when, under the action of external force,one body moves or tends to move relative to the other.3.1.3 kinetic coeffcient of frictionthe coefficient of friction under conditions
12、of macroscopic relative motion between twobodies.3.1.4 lubricantany substance interposed between two surfaces for the purpose of reducing the friction and wear between them.3.2 Definitions Not Covered by Terminology G40:1 This test method is under the jurisdiction of ASTM Committee G02 on Wear and E
13、rosion and is the direct responsibility of Subcommittee G02.50 on Friction.Current edition approved May 1, 2006Nov. 15, 2013. Published May 2006December 2013. Originally approved in 2006. Last previous edition approved in 2006 as G182 06. DOI: 10.1520/G0182-06.10.1520/G0182-13.2 For referencedASTM s
14、tandards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of a
15、n ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as publi
16、shed by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.1 breakaway coeffcient of rolling frictionthe force in the direction of rolling (F) required to produce rolling of a revolutesh
17、ape shape that is capable of rolling on a surface, divided by the normal force (N) on the revoluterolling shape:rolling5FN (1)3.2.2 inclined planea surface that can be raised at an angle to produce motion of an object on the plane.3.2.3 plain bearingsa cylindrical shape used to support a rotating sh
18、aft.3.2.4 rollingmotion of revolute shape (ball, wheel, roller, and so forth) in a specific direction, on a surface such that there isno relative slip in all or part of the area of contact.3.2.4 rolling element bearingballs or rollers in raceways that support a shaft and allow rotation of the shaft
19、or bearing outerrace (OD).4. Summary of Test Method4.1 This test method can be used to measure the breakaway rolling friction characteristics of rolling element bearings.4.2 Small rolling element bearings (less than 100 mm outside diameter) are affixed to a balanced rider and placed on an incline.Th
20、e rider is designed so that it becomes the axle about which the bearing rotates. The inclined plane is raised (by hand ormechanism) until the outer race (OD) of the bearing starts to roll on the inclined plane. The inclined plane surface is covered witha plasticized PVC tape to increase the static f
21、riction between the outside surface of the bearing and inclined plane. The test willnot yield rolling friction characteristics if the bearing slides rather than rolls on the inclined plane.4.3 The rolling friction characteristics measured by this test are the net result of the bearing design, materi
22、als and state oflubrication. Thus this test could also be used to evaluate bearing designs and bearing greases.5. Significance and Use5.1 This test is a simple, effective way of determining the ability of bearings to roll freely. Most bearing manufacturers do notsupply information on the breakaway f
23、riction coefficient of their products and if this is a design factor, users often buy candidatebearings and try them until they find one that appears to operate freer than the others. This test allows quantification of thebreakaway friction characteristics of bearings. This test assesses the frictio
24、n of a bearing as a tribosystem which includes itsconstruction and lubrication. It has shown to correlate with use. If a bearing has a low breakaway angle in this test, its breakawayfriction will be lower in service than the same size bearings that displayed a higher breakaway angle in this test.5.2
25、 Breakaway friction of bearings is important in instruments where forces are light and the bearings are used as pivots ratherthan for continued rotation. Low friction is often imperative for proper device operation.5.3 Bearings with low breakaway friction are often sought for web handling rollers. M
26、any rollers are driven only by tangentialweb contact and slippage can often damage the web. Low friction bearings are required.5.4 This test is useful for screening bearings for any applications where breakaway friction is a design concern.6. Apparatus6.1 Bearing AxleThe test bearing is clamped betw
27、een two tapered plugs assembled on the threaded-rod rider shown in Fig.1. The tapered plugs are tightened such that the inner race of the bearing is fixed to and centered on the horizontal portion of thethreaded rod.6.2 WeightsThe normal force of the bearing on the inclined plane is produced by the
28、cumulative mass of the bearing and therider assembly that holds the bearing. The weight of the rider (without the bearing) shall be 90 to 100 g and the assembly shouldweigh between 100 and 130 g. The assembled test bearing and rider should weigh the same for each test bearing. Weights in theform of
29、bushings or washers can be affixed to the axle portion of the rider to make all test assemblies have the same weight (65g). Weights must be added in pairs with equal amounts on each side of the rider.6.3 Inclined PlaneThe inclined plane should be from 20 to 30 mm wide, a minimum of 250 mm long, be a
30、 rigid material (hardplastic, metal, etc.) and be capable of being raised on a pivot and locked in place at the rider breakaway angle. The inclined planeshould be high enough to allow unobstructed rolling of the rider down the plane (Fig. 2).6.4 Rolling SurfaceThe inclined plane should be covered by
31、 a single layer of 127/152 m inch-thick plasticized PVC tape(black electrical tape) with the pressure sensitive adhesive (PSA) surface adhered to the plane. The tape must be wider than thetest bearing by at least 2 mm on each side. The purpose of the tape is to increase the friction between the oute
32、r race and the inclinedplane. Tests with Test Method G143 capstan friction test identified this material as having high friction ( 0.5) against hardenedsteel. If the outer race slides on the inclined plane before the bearing rotates, the result will be sliding friction, not rolling friction.Fiduciar
33、y marks can be used to verify that the bearing does not slide.G182 1326.5 Angle MeasurementThe test metric is the inclination of the inclined plane when rider motion occurs. This angle can bemeasured by a protractor or by calibration of a gage on the device. Some inclined planes use an electronic en
34、coder to yield theangle. The least count on the angle measuring device shall be 1 degree.NOTE 1User must determine weight and center of gravity. All components to be made from brass or steel.FIG. 1 Suggested Balancing ArmFIG. 2 Schematic of Test RigG182 1337. Test Procedure7.1 Sample PreparationBear
35、ings are to be tested in the condition that they will be used. Rolling friction is affected by thebearing design (separators, clearances, materials, and so forth) and lubrication. The outside diameter should be degreased with asolvent such as acetone in such a way that the cleaning solvent does not
36、get into the lubricant or rolling elements. A wipe withan acetone soaked cloth is usually adequate. A fresh strip of black electrical tape should be applied to the rolling surface on theinclined plane using cotton gloves to prevent surface contamination. The tape should not be touched or contaminate
37、d in any way.7.2 Assemble the cleaned bearing on the rider axle making sure that it freely rotates about the axle (partial manual revolution),to ensure proper seating of the tapered cones.7.3 Test ConditionsConduct tests with relative humidity between 35 and 75 % and at a temperature of 20 6 3C. Con
38、ditionsamples for 24 h in the test atmosphere prior to testing.7.4 Conducting the TestLevel the test apparatus to within 1/50 cm in longitudinal and transverse directions and place the rideron the tape-covered plane (Fig. 2). Raise the sample plane until the bearing just starts to roll. Fiduciary ma
39、rks on the plane andbearing outside diameter can be used to verify rolling. Motion of the sample plane should be slow and not to exceed 1/s and besteady. Record this angle.7.4.1 Repeat the procedure twice more and calculate the average of the three angle determinations.7.4.2 Do not spin the bearing
40、races before or during testing unless this is the way that they will be used in service. Test the waybearings will be used in service. Usually this test will be used to compare the same nominal size bearings for breakaway friction,so bearing mass differences are not a concern.Appropriate weights (se
41、e Note 1) can be added to the balance arm to produce equalrider mass for testing bearings with weight differences.NOTE 1Add washers at the back of the cones that clamp the inner race.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
42、description and condition of the test counterface,8.1.3 The average breakaway of rolling friction (r) of the test 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 test environment.8.2 Interpretation
43、of ResultsThe test is intended to identify free-rolling bearings from sticky bearings. High coefficients ofvariation can be an indicator of a sticky bearing.9. Precision and Bias9.1 The test variability in interlaboratory tests on seven ball bearings is illustrated in Fig. 3. The conditional data ar
44、e analyzedper G117 in Appendix X1.FIG. 3 Within-Lab ResultsG182 1349.1.1 The within-laboratory coefficient of variation was in the range of 9.21 to 22.2 %. The average for five laboratories was14 %. The average 95 % confidence limit was 0.03. The between-laboratory variability (COV) ranged from 22.9
45、 to 75 %. Theaverage was 46 %. The average 95 % confidence limit was 0.1.9.2 BiasThere is no absolute value of friction coefficient. It is a product of a tribosystem. Therefore, the value can have nobias. magnitude of the value cannot be determined. Some of the factors that can affect reproducibilit
46、y and repeatability problemsare: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 Imbalance of the bearing holder, and9.2.5 Significant differences in bearing size (see Note 2) (when comparing bearings).NOTE 2The bear
47、ing assembly in interlaboratory tests varied in weight between 100 and 130 g. These differences were ignored to keep the test simple.Future interlaboratory test will keep assembly weight the same for a group of test bearings.10. Keywords10.1 coefficient of rolling friction; friction testing; rolling
48、; rolling frictionG182 135ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infrin
49、gement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee 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 meeting of theresponsible technical committee, which you may attend. If you feel that your comments have no
