1、Designation: G 194 08Standard Test Method forMeasuring Rolling Friction Characteristics of a SphericalShape on a Flat Horizontal Plane1This standard is issued under the fixed designation G 194; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 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 a sphere or near
3、ly 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 playing surface
4、s, 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 by the spherical
5、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 interestusing a standard
6、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 example, the rollingr
7、esistances 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 for are appropriate for differenttypes of sphe
8、rical shapes. If a sphere of interest cannot beaccommodated with using one of the launch ramps discussed inAppendix X1 andAppendix 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 asstandard. No other
9、 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 and health practices and determine the applica-bility of
10、regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2G40 Terminology Relating to Wear and ErosionG115 Guide for Measuring and Reporting Friction Coeffi-cientsG 143 Test Method for Measurement of Web/Roller Fric-tion Characteristics3. Terminology3.1 Definitions:3.1.1 rolling
11、 friction force, nin tribology, a force, oppo-site to the direction of rolling, resisting rolling of a sphericalshape, ball, roller, wheel, etc. forced against and rolling in adirection on another surface. G403.2 Definitions of Terms Specific to This Standard:3.2.1 coeffcient of rolling resistance (
12、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 thehorizontal plane divided by the distance rolled on t
13、he horizon-tal plane after leaving the launch ramp.3.2.2 rolling resistance number (RR), ndimensionlessmeasure of the retardation produced on a spherical shaperolling on a flat horizontal surface: the higher the number, thehigher the retardation. This number is obtained by multiplyingthe CORR by 100
14、.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 surface of interest and a sphere (ball bearing,orange, golf ball, etc.) is rolled down the ramp onto the testsurface. The distance traveled af
15、ter exiting the ramp is mea-sured. The ratio of the height of the spherical shapes outside1This 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 Nov. 1, 2008. Published January
16、2009.2For 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 ASTM International, 100 Barr Harbor Drive, PO
17、 Box C700, West Conshohocken, PA 19428-2959, United States.diameter above the test surface (plane) to the distance rolledafter leaving the ramp is the coefficient of rolling resistance.The test concept is that the potential energy of the sphere raisedto a height (mass 3 height) is equated to the rol
18、ling energy ofthe released sphere (mass 3 distance rolled). The energy ismanifested in distance traveled after leaving the launch ramp.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 compar
19、e the rollingcharacteristics of different spherical shapes/surface textures ona constant rolling surface or a constant spherical shape ondifferent rolling surfaces to compare ease of rolling. Differentshaped ramps and angles are have been used for differentspherical objects (Appendix X2). Data devel
20、oped with oneprocedure cannot be readily compared with data developedusing one of the other procedures since the spherical shapes,launch 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 in
21、volves the nature of therolling surface and the counterface. The sliding friction force(F) is usually considered to be the sum of forces arising fromdeformations of surface features (Fs), from attractive forces(atomic, molecular, etc.) at contact points (Fa) and force frominteraction of films and pa
22、rticulates on the rubbing surfaces(Ff):F 5 Fa1 Fs1 Ff(1)The rolling friction force includes these force contributionsplus effects from the relative stiffness of the contactingsurfaces, the diameter (curvature) of the spherical shape (ball,orange, etc.) and other factors. Because there are so manyfac
23、tors involved in a rolling tribosystem, rolling resistance canbest be quantified by an actual test of the sphere of interest onthe intended counterface, as in this test method.5.2 There are countless applications where it is important toquantify the rolling characteristics of a particular sphericals
24、hape on a particular surface. The interlaboratory tests con-ducted for this test method were performed on hardened steelballs like those used in ball bearings. This test method could beused to assess the effect of different counterface surfaces on therolling characteristics of balls for ball bearing
25、s. Conversely, itcould be used as a quality control test on balls. Surfaceimperfections/defects/films, etc. on the balls can affect howthey roll: the distance traveled on a common counterface.5.3 Industrial applications of this test method can includeassessing conveying surfaces for spherical or nea
26、rly specialparts: check valve balls, cabinet knobs, Christmas ornaments,toilet floats, etc. Many medical devices use special shapeswhere rolling characteristics are a consideration. Similarly,many pharmaceutical products (pills) are spherical or nearlyspherical in shape, and this test method can be
27、used to assessrolling characteristics for conveying or other reasons such assize (mass) check.5.4 Rolling friction of spherical shapes can be a consider-ation in countless sports (soccer, golf, lacrosse, etc.) and gameapplications (billiards, bocce, toys, etc.). This test method canbe used to rank t
28、he rolling resistance of different ball compo-sitions, masses, shapes, surface textures, design, stiffness, etc.Similarly, the test method can be used to assess the ease ofrolling of balls on different playing or game surfaces.5.5 This test method is very applicable to spherical ormostly spherical f
29、ood products. For example, it is common touse rolling distance of apples, citrus, nuts, etc. to classify themby size for marketing. They are rolled down an angled surfaceand the rolling distance becomes a function of size (mass/diameter). This test method can be used to assess the suitabilityof vari
30、ous rolling surfaces (carpet, metal, wood, etc.) forsuitability in classification equipment. It could also be used forfood conveyance on spherical-shaped processed foods (gum-balls, hard candy, meatballs, etc.)5.6 Finally, this test method can be a valuable teaching toolfor physics and tribology stu
31、dents. The equipment is simple,low cost and student proof. It can be used to demonstrate theconcept of rolling friction and the factors that affect it.6. Apparatus6.1 A typical launch ramp for small-diameter balls is shownin Fig. X2.1. The ramp can be made from any metal with acold-finished surface
32、roughness in the range of 0.1 and 0.3-mroughness average. Corrosion-resistant materials (aluminum,stainless steel) are preferred as the material 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 schemat
33、ic that includes thenecessary design elements of a suitable launch ramp. Thedistance rolled after the spherical shape leaves the ramp (d) isthe test 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
34、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 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 surfa
35、ceof interest.7.1.2 Remove all obvious films and debris from handlingon the ramp, sphere, and counterface.7.1.3 Place the sphere at 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 fin
36、gers 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 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 e
37、xample, 31.3 cm).7.1.6 Calculate the coefficient of rolling resistance (CORR)for the tribosystem using the following equation:CORR 5 h/d (2)G194082CORR = may be converted to RR by multiplying by 100.This term may be preferred for some applicationssince it usually results in a whole number (afterroun
38、ding) that increases with rolling resistance orrolling frictionh = the vertical distance between the spheres point ofcontact with the 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
39、is not necessary touse a new travel path for each test if the rolling surface isrobust and not irreversibly deformed during testing.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
40、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 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 membe
41、r andthe rolling counterface. For example, the newness, conditionand cleanliness of a sphere should be stated along withpertinent counterface conditions such as method of manufac-ture, surface texture, etc. Helpful documents for recording dataare Guide G115and Test Method G 143. A typical test repor
42、tis shown in Fig. 2.9. Precision and Bias9.1 There is no standard rolling surface that can be evalu-ated with this test method, therefore, 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 o
43、n precision surface plates. The testballs came from the same lot. The surface plates were ofdifferent materials, but all were level 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 developme
44、nt of this test method.Coefficient of variation in these tests ranged from 0.04 to 0.12.9.2 Sources of VariabilityNicks and other discontinuitiesand films on the test ramp or rolling surface can affect testresults.10. Keywords10.1 balls; coefficient of rolling friction; plane; rollingfriction; spher
45、esNOTEThe launch ramp dimensions used in Option B tests were:l=40cm,h=13cm,Vee = 110, u = 20,Material = cold rolled 6061T6 aluminum.FIG. 1 Schematic of a Typical Launch RampDate:Time:Material Couple:Rolling elementRolling surfaceTest Conditions:TemperatureRelative humidityRamp heightRamp lengthOther
46、Results:Rolling distancesAverageStd. deviationCoefficient of rollingresistance (CORR)Rolling resistance (RR)FIG. 2 Rolling Friction Test ReportG194083APPENDIXES(Nonmandatory Information)X1. INTERLABORATORY TEST RESULTSX1.1 TestsX1.1.1 Tests were conducted using 6.3-mm and 9.5-mmdiameter 52100 harden
47、ed 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 di
48、fferent for eachrolling surface because the rolling surfaces were different inmaterial, surface texture, cleanliness, etc. Thus, these datashow within-lab test variability, not between lab variability.See Table X1.1.TABLE X1.1 Distance Rolled after Leaving the Launch RampTest 6.3-mm ball 9.5-mm ball
49、Lab 1 (BLS) Stainless steel optical bench120 26221 832 742 3052262 17 21.5 29820 392210 19 27x = 20.75s=1.08COV=0.05x = 29.2s=2.3COV=0.08Test 6.3-mm ball 9.5-mm ballLab 2 (IT) Granite surface plate1 37.5 572 36.2 58.43 39.7 59.34 40 58.75 36.2 58.76 37.1 57.57 37.6 59.88 36.5 599 37.1 5710 40.3 60x = 37.8s=1.6COV=0.04x = 58.8s=1.1COV=0.02Test 6.3-mm ball 9.5-mm ballLab 3 (BLN) Cast iron surface plate116 721 3231417516 1621 367 18.5 29819 16.5 3410 17 30x=17s=1.6COV=0.09x = 31.6s=2.5COV=0.08G194084TABLE X1.1 ContinuedTest 6.3-mm ball 9.5-mm ballLab 4 (CMM) Granite sur
