1、Designation: G194 08 (Reapproved 2018)Standard Test Method forMeasuring Rolling Friction Characteristics of a SphericalShape on a Flat Horizontal Plane1This standard is issued under the fixed designation G194; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the 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 covers the use of an angled launchramp to initiate rolling of
3、a sphere or nearly spherical shape ona flat horizontal surface to determine the rolling frictioncharacteristics of a given spherical shape on a given surface.1.1.1 Steel balls on a surface plate were used in interlabo-ratory tests (see Appendix X1). Golf balls on a green, soccerand lacrosse balls on
4、 playing surfaces, bowling balls on an alane, basketballs on hardwood, and marbles on compositesurface were tested in the development of this test method, butthe test applies to any sphere rolling on any flat horizontalsurface.1.1.2 The rolling friction of spheres on horizontal surfaces isaffected b
5、y the spherical shapes stiffness, radius of curvature,surface texture, films on the surface, the nature of the counter-face surface; there are many factors to consider. This testmethod takes all of these factors into consideration. Thespherical shape of interest is rolled on the surface of interestu
6、sing a standard ramp to initiate rolling and standard tech-niques to measure and treat the rolled distance after leaving theramp.1.1.3 This test method produces a rolling resistance numberon a specific spherical shape on a specific surface. It is intendedfor comparing similar tribosystems. For examp
7、le, the rollingresistances of marbles on a particular surface are not to becompared with the rolling resistance of soccer balls on grass,because their masses and diameters are very different as are thecounterface surfaces on which they roll.1.1.4 Different launch ramps are appropriate for differentt
8、ypes of spherical shapes. If a sphere of interest cannot beaccommodated with using one of the launch ramps discussed inAppendix X1 and Appendix X2, a different launch ramp can bedeveloped and added with future revisions to this test method.1.2 The values stated in SI units are to be regarded asstand
9、ard. 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 det
10、er-mine 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-menda
11、tions issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2G40 Terminology Relating to Wear and ErosionG115 Guide for Measuring and Reporting Friction Coeffi-cientsG143 Test Method for Measurement of Web/Roller FrictionCharacter
12、istics3. Terminology3.1 Definitions:3.1.1 rolling friction force, nin tribology, a force, oppositeto the direction of rolling, resisting rolling of a spherical shape,ball, roller, wheel, etc. forced against and rolling in a directionon another surface. G403.2 Definitions of Terms Specific to This St
13、andard:3.2.1 coeffcient of rolling resistance (CORR)dimensionless measure of rolling retardation experienced by aspherical shape (sphere and the like) on a flat horizontal planeof interest; it is the ratio of the vertical distance between thespheres point of contact with the launch ramp and thehoriz
14、ontal plane divided by the distance rolled on the horizon-tal plane after leaving the launch ramp.3.2.2 rolling resistance number (RR), ndimensionlessmeasure of the retardation produced on a spherical shape1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is th
15、e direct responsibility of Subcommittee G02.50 on Friction.Current edition approved June 1, 2018. Published July 2018. Originally approvedin 2008. Last previous edition approved in 2013 as G194 08 (2013). DOI:10.1520/G0194-08R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, o
16、rcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandardsvolume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international s
17、tandard was developed in 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.1ro
18、lling on a flat horizontal surface: the higher the number, thehigher the retardation. This number is obtained by multiplyingthe CORR by 100.4. Summary of Test Method4.1 A vee-shaped launch ramp with known height, lengthand vee angle is placed on a flat and level (most flat and levelportion) of a sur
19、face of interest and a sphere (ball bearing,orange, golf ball, etc.) is rolled down the ramp onto the testsurface. The distance traveled after exiting the ramp is mea-sured. The ratio of the height of the spherical shapes outsidediameter above the test surface (plane) to the distance rolledafter lea
20、ving the ramp is the coefficient of rolling resistance.The test concept is that the potential energy of the sphere raisedto a height (mass height) is equated to the rolling energy ofthe released sphere (mass distance rolled). The energy ismanifested in distance traveled after leaving the launch ramp
21、.The distance traveled is the test metric, and this distance isaffected by the nature of the spherical shape and rollingsurface. The test method can be used to compare the rollingcharacteristics of different spherical shapes/surface textures ona constant rolling surface or a constant spherical shape
22、 ondifferent rolling surfaces to compare ease of rolling. Differentshaped ramps and angles have been used for different sphericalobjects (Appendix X2). Data developed with one procedurecannot be readily compared with data developed using one ofthe other procedures since the spherical shapes, launch
23、ramps,and rolling surfaces are different.5. Significance and Use5.1 Rolling friction like sliding friction depends upon manyfactors. It is a system effect that involves the nature of therolling surface and the counterface. The sliding friction force(F) is usually considered to be the sum of forces a
24、rising fromdeformations of surface features (Fs), from attractive forces(atomic, molecular, etc.) at contact points (Fa) and force frominteraction of films and particulates on the rubbing surfaces(Ff):F 5 Fa1Fs1Ff(1)The rolling friction force includes these force contributionsplus effects from the r
25、elative stiffness of the contactingsurfaces, the diameter (curvature) of the spherical shape(ball, orange, etc.) and other factors. Because there are somany factors involved in a rolling tribosystem, rolling resis-tance can best be quantified by an actual test of the sphereof interest on the intende
26、d counterface, as in this testmethod.5.2 There are countless applications where it is important toquantify the rolling characteristics of a particular sphericalshape on a particular surface. The interlaboratory tests con-ducted for this test method were performed on hardened steelballs like those us
27、ed in ball bearings. This test method could beused to assess the effect of different counterface surfaces on therolling characteristics of balls for ball bearings. Conversely, itcould be used as a quality control test on balls. Surfaceimperfections/defects/films, etc. on the balls can affect howthey
28、 roll: the distance traveled on a common counterface.5.3 Industrial applications of this test method can includeassessing conveying surfaces for spherical or nearly specialparts: check valve balls, cabinet knobs, Christmas ornaments,toilet floats, etc. Many medical devices use special shapeswhere ro
29、lling characteristics are a consideration. Similarly,many pharmaceutical products (pills) are spherical or nearlyspherical in shape, and this test method can be used to assessrolling characteristics for conveying or other reasons such assize (mass) check.5.4 Rolling friction of spherical shapes can
30、be a consider-ation in countless sports (soccer, golf, lacrosse, etc.) and gameapplications (billiards, bocce, toys, etc.). This test method canbe used to rank the rolling resistance of different ballcompositions, masses, shapes, surface textures, design,stiffness, etc. Similarly, the test method ca
31、n be used to assessthe ease of rolling of balls on different playing or gamesurfaces.5.5 This test method is very applicable to spherical ormostly spherical food products. For example, it is common touse rolling distance of apples, citrus, nuts, etc. to classify themby size for marketing. They are r
32、olled down an angled surfaceand the rolling distance becomes a function of size (mass/diameter). This test method can be used to assess the suitabilityof various rolling surfaces (carpet, metal, wood, etc.) forsuitability in classification equipment. It could also be used forfood conveyance on spher
33、ical-shaped processed foods(gumballs, hard candy, meatballs, etc.)5.6 Finally, this test method can be a valuable teaching toolfor physics and tribology students. The equipment is simple,low cost and student proof. It can be used to demonstrate theconcept of rolling friction and the factors that aff
34、ect it.6. Apparatus6.1 Atypical launch ramp for small-diameter balls is shownin Fig. X2.1. The ramp can be made from any metal with acold-finished surface roughness in the range of 0.1 and 0.3-mroughness average. Corrosion-resistant materials (aluminum,stainless steel) are preferred as the material
35、of construction ofthe launch ramp since the rolling surface can be subject tocorrosion from rain, dew, handling, etc.6.2 Fig. 1 shows a launch ramp schematic that includes thenecessary design elements of a suitable launch ramp. Thedistance rolled after the spherical shape leaves the ramp (d) isthe t
36、est metric. These design elements are:(1) A vee shape to cradle the sphere.(2) A reference surface that locates the sphere at the top ofthe ramp.(3) Aramp height (h), length (l), and angles (vee and ramp)() suitable for the size and mass of the sphere (AppendixX2.1).(4) The delivery end of the ramp
37、must be tapered tominimize “drop-off” as the sphere exits the ramp.7. Procedure7.1 Test Procedure:7.1.1 Place the launch ramp on the flat, horizontal surface ofinterest.7.1.2 Remove all obvious films and debris from handling onthe ramp, sphere, and counterface.G194 08 (2018)27.1.3 Place the sphere a
38、t the top of the launch ramp touchingthe reference surface.7.1.4 Release the sphere without added sideward, forward,or backward forces. Small balls can be held in two fingers andreleased; large balls can be held with both hands or a devicecan be used to hold the ball until release.7.1.5 Measure the
39、distance traveled from the launch rampend with a meter stick, tape measure, etc. If the rollingdistances are less than 500 cm, round the result to one decimalplace (for example, 31.3 cm).7.1.6 Calculate the coefficient of rolling resistance (CORR)for the tribosystem using the following equation:CORR
40、 5 h/d (2)where:CORR = may be converted to RR by multiplying by 100.This term may be preferred for some applicationssince it usually results in a whole number (afterrounding) that increases with rolling resistance orrolling frictionh = the vertical distance between the spheres point ofcontact with t
41、he launch ramp and the horizontalrolling plane.d = the distance that the sphere rolled (to a stop) afterexiting the inclined plane7.2 Ten replicates are recommended. It is not necessary touse a new travel path for each test if the rolling surface isrobust and not irreversibly deformed during testing
42、.NOTE 1The length of the ramp is neglected in the CORR calculation.Its length is neglected because this length just becomes a constant addedto the (d) measurements made in the test. It does play a role in retardingthe rolling of the sphere and it must be kept clean and debris free. Dataobtained with
43、 one ramp should not be compared with data obtained witha launch ramp with a different height and length.8. Report8.1 It is important to describe fully the rolling member andthe rolling counterface. For example, the newness, conditionand cleanliness of a sphere should be stated along withpertinent c
44、ounterface conditions such as method ofmanufacture, surface texture, etc. Helpful documents for re-cording data are Guide G115 and Test Method G143. A typicaltest report is shown in Fig. 2.9. Precision and Bias9.1 There is no standard rolling surface that can be evalu-ated with this test method, the
45、refore, no bias can be defined.9.1.1 Appendix X1 shows results of interlaboratory testsconducted with two different diameter hardened (60 HRC)52100 steel balls rolling on precision surface plates. The testballs came from the same lot. The surface plates were ofdifferent materials, but all were level
46、 and flat within 50 m in30 cm. The coefficient of variation ranged from 0.02 to 0.108.9.1.2 Appendix X2.1 contains nonmandatory informationon ramps used in the development of this test method.Coefficient of variation in these tests ranged from 0.04 to 0.12.9.2 Sources of VariabilityNicks and other d
47、iscontinuitiesand films on the test ramp or rolling surface can affect testresults.NOTE 1The launch ramp dimensions used in Option B tests were:l=40cm,h=13cm,Vee = 110, = 20,Material = cold rolled 6061T6 aluminum.FIG. 1 Schematic of a Typical Launch RampDate:Time:Material Couple:Rolling elementRolli
48、ng surfaceTest Conditions:TemperatureRelative humidityRamp heightRamp lengthOtherResults:Rolling distancesAverageStd. deviationCoefficient of rollingresistance (CORR)Rolling resistance(RR)FIG. 2 Rolling Friction Test ReportG194 08 (2018)310. Keywords10.1 balls; coefficient of rolling friction; plane
49、; rollingfriction; spheresAPPENDIXES(Nonmandatory Information)X1. INTERLABORATORY TEST RESULTSX1.1 TestsX1.1.1 Tests were conducted using 6.3-mm and 9.5-mmdiameter 52100 hardened steel (60 HRC) balls on precisionsurfaces (surface plates, optical bench).Launch ramp height: 0.5/0.55 cm,Length: 13.4/14.5 cm,Vee angle: 110/120,Material: 6061T6 aluminum, cold finished.X1.2 AnalysisX1.2.1 The coefficient of variation ranged from 0.02 to0.108. The absolute distance values are different for eachrolling surface because the rolling surfaces were different inmaterial,
