ASTM G194-08(2013)
(Test Method)Standard Test Method for Measuring Rolling Friction Characteristics of a Spherical Shape on a Flat Horizontal Plane
Standard Test Method for Measuring Rolling Friction Characteristics of a Spherical Shape on a Flat Horizontal Plane
SIGNIFICANCE AND USE
5.1 Rolling friction like sliding friction depends upon many factors. It is a system effect that involves the nature of the rolling surface and the counterface. The sliding friction force (F) is usually considered to be the sum of forces arising from deformations of surface features (Fs), from attractive forces (atomic, molecular, etc.) at contact points (Fa) and force from interaction of films and particulates on the rubbing surfaces (Ff):
The rolling friction force includes these force contributions plus effects from the relative stiffness of the contacting surfaces, the diameter (curvature) of the spherical shape (ball, orange, etc.) and other factors. Because there are so many factors involved in a rolling tribosystem, rolling resistance can best be quantified by an actual test of the sphere of interest on the intended counterface, as in this test method.
5.2 There are countless applications where it is important to quantify the rolling characteristics of a particular spherical shape on a particular surface. The interlaboratory tests conducted for this test method were performed on hardened steel balls like those used in ball bearings. This test method could be used to assess the effect of different counterface surfaces on the rolling characteristics of balls for ball bearings. Conversely, it could be used as a quality control test on balls. Surface imperfections/defects/films, etc. on the balls can affect how they roll: the distance traveled on a common counterface.
5.3 Industrial applications of this test method can include assessing conveying surfaces for spherical or nearly special parts: check valve balls, cabinet knobs, Christmas ornaments, toilet floats, etc. Many medical devices use special shapes where rolling characteristics are a consideration. Similarly, many pharmaceutical products (pills) are spherical or nearly spherical in shape, and this test method can be used to assess rolling characteristics for conveying or other reasons such ...
SCOPE
1.1 This test method covers the use of an angled launch ramp to initiate rolling of a sphere or nearly spherical shape on a flat horizontal surface to determine the rolling friction characteristics of a given spherical shape on a given surface.
1.1.1 Steel balls on a surface plate were used in interlaboratory tests (see Appendix X1). Golf balls on a green, soccer and lacrosse balls on playing surfaces, bowling balls on an a lane, basketballs on hardwood, and marbles on composite surface were tested in the development of this test method, but the test applies to any sphere rolling on any flat horizontal surface.
1.1.2 The rolling friction of spheres on horizontal surfaces is affected by the spherical shape’s stiffness, radius of curvature, surface texture, films on the surface, the nature of the counterface surface; there are many factors to consider. This test method takes all of these factors into consideration. The spherical shape of interest is rolled on the surface of interest using a standard ramp to initiate rolling and standard techniques to measure and treat the rolled distance after leaving the ramp.
1.1.3 This test method produces a rolling resistance number on a specific spherical shape on a specific surface. It is intended for comparing similar tribosystems. For example, the rolling resistances of marbles on a particular surface are not to be compared with the rolling resistance of soccer balls on grass, because their masses and diameters are very different as are the counterface surfaces on which they roll.
1.1.4 Different launch ramps for are appropriate for different types of spherical shapes. If a sphere of interest cannot be accommodated with using one of the launch ramps discussed in Appendix X1 and Appendix X2, a different launch ramp can be developed and added with future revisions to this test method.
1.2 The values stated in SI units are to be regarded as standard. No other units of m...
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Standards Content (Sample)
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Designation: G194 − 08 (Reapproved 2013)
Standard Test Method for
Measuring Rolling Friction Characteristics of a Spherical
Shape on a Flat Horizontal Plane
This standard is issued under the fixed designation G194; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers the use of an angled launch
responsibility of the user of this standard to establish appro-
ramptoinitiaterollingofasphereornearlysphericalshapeon
priate safety and health practices and determine the applica-
a flat horizontal surface to determine the rolling friction
bility of regulatory limitations prior to use.
characteristics of a given spherical shape on a given surface.
1.1.1 Steel balls on a surface plate were used in interlabo-
2. Referenced Documents
ratory tests (see Appendix X1). Golf balls on a green, soccer
2.1 ASTM Standards:
and lacrosse balls on playing surfaces, bowling balls on an a
G40Terminology Relating to Wear and Erosion
lane, basketballs on hardwood, and marbles on composite
G115Guide for Measuring and Reporting Friction Coeffi-
surface were tested in the development of this test method, but
cients
the test applies to any sphere rolling on any flat horizontal
G143Test Method for Measurement of Web/Roller Friction
surface.
Characteristics
1.1.2 Therollingfrictionofspheresonhorizontalsurfacesis
affected by the spherical shape’s stiffness, radius of curvature,
3. Terminology
surface texture, films on the surface, the nature of the counter-
3.1 Definitions:
face surface; there are many factors to consider. This test
3.1.1 rolling friction force, n—in tribology,aforce,opposite
method takes all of these factors into consideration. The
tothedirectionofrolling,resistingrollingofasphericalshape,
spherical shape of interest is rolled on the surface of interest
ball, roller, wheel, etc. forced against and rolling in a direction
using a standard ramp to initiate rolling and standard tech-
on another surface. G40
niquestomeasureandtreattherolleddistanceafterleavingthe
ramp.
3.2 Definitions of Terms Specific to This Standard:
1.1.3 This test method produces a rolling resistance number
3.2.1 coeffıcient of rolling resistance (CORR)—
onaspecificsphericalshapeonaspecificsurface.Itisintended
dimensionless measure of rolling retardation experienced by a
for comparing similar tribosystems. For example, the rolling
spherical shape (sphere and the like) on a flat horizontal plane
resistances of marbles on a particular surface are not to be
of interest; it is the ratio of the vertical distance between the
compared with the rolling resistance of soccer balls on grass,
sphere’s point of contact with the launch ramp and the
becausetheirmassesanddiametersareverydifferentasarethe
horizontal plane divided by the distance rolled on the horizon-
counterface surfaces on which they roll.
tal plane after leaving the launch ramp.
1.1.4 Differentlaunchrampsforareappropriatefordifferent
3.2.2 rolling resistance number (RR), n—dimensionless
types of spherical shapes. If a sphere of interest cannot be
measure of the retardation produced on a spherical shape
accommodatedwithusingoneofthelaunchrampsdiscussedin
rolling on a flat horizontal surface: the higher the number, the
AppendixX1andAppendixX2,adifferentlaunchrampcanbe
higher the retardation. This number is obtained by multiplying
developed and added with future revisions to this test method.
the CORR by 100.
1.2 The values stated in SI units are to be regarded as
4. Summary of Test Method
standard. No other units of measurement are included in this
standard.
4.1 A vee-shaped launch ramp with known height, length
and vee angle is placed on a flat and level (most flat and level
This test method is under the jurisdiction of ASTM Committee G02 on Wear
and Erosion and is the direct responsibility of Subcommittee G02.50 on Friction. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 15, 2013. Published November 2013. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2008. Last previous edition approved in 2008 as G194 – 08. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0194-13. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G194 − 08 (2013)
portion) of a surface of interest and a sphere (ball bearing, 5.4 Rolling friction of spherical shapes can be a consider-
orange, golf ball, etc.) is rolled down the ramp onto the test ation in countless sports (soccer, golf, lacrosse, etc.) and game
surface. The distance traveled after exiting the ramp is mea- applications (billiards, bocce, toys, etc.). This test method can
sured. The ratio of the height of the spherical shape’s outside be used to rank the rolling resistance of different ball
diameter above the test surface (plane) to the distance rolled compositions, masses, shapes, surface textures, design,
after leaving the ramp is the coefficient of rolling resistance. stiffness, etc. Similarly, the test method can be used to assess
Thetestconceptisthatthepotentialenergyofthesphereraised the ease of rolling of balls on different playing or game
to a height (mass × height) is equated to the rolling energy of surfaces.
the released sphere (mass × distance rolled). The energy is
5.5 This test method is very applicable to spherical or
manifested in distance traveled after leaving the launch ramp.
mostly spherical food products. For example, it is common to
The distance traveled is the test metric, and this distance is
use rolling distance of apples, citrus, nuts, etc. to classify them
affected by the nature of the spherical shape and rolling
by size for marketing. They are rolled down an angled surface
surface. The test method can be used to compare the rolling
and the rolling distance becomes a function of size (mass/
characteristics of different spherical shapes/surface textures on
diameter).Thistestmethodcanbeusedtoassessthesuitability
a constant rolling surface or a constant spherical shape on
of various rolling surfaces (carpet, metal, wood, etc.) for
different rolling surfaces to compare ease of rolling. Different
suitability in classification equipment. It could also be used for
shaped ramps and angles are have been used for different
food conveyance on spherical-shaped processed foods
spherical objects (Appendix X2). Data developed with one
(gumballs, hard candy, meatballs, etc.)
procedure cannot be readily compared with data developed
5.6 Finally, this test method can be a valuable teaching tool
using one of the other procedures since the spherical shapes,
for physics and tribology students. The equipment is simple,
launch ramps, and rolling surfaces are different.
low cost and student proof. It can be used to demonstrate the
5. Significance and Use
concept of rolling friction and the factors that affect it.
5.1 Rolling friction like sliding friction depends upon many
6. Apparatus
factors. It is a system effect that involves the nature of the
6.1 Atypicallaunchrampforsmall-diameterballsisshown
rolling surface and the counterface. The sliding friction force
in Fig. X2.1. The ramp can be made from any metal with a
(F) is usually considered to be the sum of forces arising from
cold-finished surface roughness in the range of 0.1 and 0.3-µm
deformations of surface features (F ), from attractive forces
s
roughness average. Corrosion-resistant materials (aluminum,
(atomic, molecular, etc.) at contact points (F ) and force from
a
stainless steel) are preferred as the material of construction of
interaction of films and particulates on the rubbing surfaces
the launch ramp since the rolling surface can be subject to
(F):
f
corrosion from rain, dew, handling, etc.
F 5 F 1F 1F (1)
a s f
6.2 Fig. 1 shows a launch ramp schematic that includes the
The rolling friction force includes these force contributions
necessary design elements of a suitable launch ramp. The
plus effects from the relative stiffness of the contacting
surfaces, the diameter (curvature) of the spherical shape
distance rolled after the spherical shape leaves the ramp (d) is
(ball, orange, etc.) and other factors. Because there are so
the test metric. These design elements are:
many factors involved in a rolling tribosystem, rolling resis-
(1)A vee shape to cradle the sphere.
tance can best be quantified by an actual test of the sphere
(2)Areference surface that locates the sphere at the top of
of interest on the intended counterface, as in this test
the ramp.
method.
(3)Arampheight(h),length(l),andangles(veeandramp)
5.2 Therearecountlessapplicationswhereitisimportantto
(°) suitable for the size and mass of the sphere (Appendix
quantify the rolling characteristics of a particular spherical
X2.1).
shape on a particular surface. The interlaboratory tests con-
(4)The delivery end of the ramp must be tapered to
ducted for this test method were performed on hardened steel
minimize “drop-off” as the sphere exits the ramp.
ballslikethoseusedinballbearings.Thistestmethodcouldbe
usedtoassesstheeffectofdifferentcounterfacesurfacesonthe 7. Procedure
rolling characteristics of balls for ball bearings. Conversely, it
7.1 Test Procedure:
could be used as a quality control test on balls. Surface
7.1.1 Placethelaunchrampontheflat,horizontalsurfaceof
imperfections/defects/films, etc. on the balls can affect how
interest.
they roll: the distance traveled on a common counterface.
7.1.2 Removeallobviousfilmsanddebrisfromhandlingon
5.3 Industrial applications of this test method can include the ramp, sphere, and counterface.
assessing conveying surfaces for spherical or nearly special 7.1.3 Placethesphereatth
...
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