ASTM G219-23

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Designation: G219 − 18 G219 − 23
Standard Guide for
Determination of Static Coefficient of Friction of Test
Couples Using an Inclined Plane Testing Device
This standard is issued under the fixed designation G219; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide is intended to standardize the use of an inclined plane testing device to measure the breakaway friction (static)
coefficient of mating couples that are of such size and shape that they can be made into a rider (one member of the sliding couple)
on a flat surface (the second member of the sliding couple) that can bestatic (breakaway) coefficient of friction between two bodies.
One body is in the form of a small “rider” (few centimeters) and the other a rectangular flat plane (50 mm to 75 mm by 400 mm).
The rider is placed on the plane and the plane is inclined at an angle to produce motion of the rider. The tangent of the angle at
which breakawaymacroscopic motion of the rider occursinitiates on the angled plane is the breakaway or static coefficient of
friction for that sliding couple.
1.2 Units—The values stated in SI units are to be regarded as the standard. No other 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 responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
G40 Terminology Relating to Wear and Erosion
G115 Guide for Measuring and Reporting Friction Coefficients
3. Terminology
3.1 Definitions:
3.1.1 friction force, n—resisting force tangential to the interface between two bodies, when under action of an external force, one
body moves or tends to move relative to the other. G40
3.1.2 static coeffıcient of friction, n—coefficient of friction corresponding to the maximum friction force that shall be overcome
to initiate macroscopic motion between two bodies. G40
This guide is under the jurisdiction of ASTM Committee G02 on Wear and Erosion and is the direct responsibility of Subcommittee G02.50 on Friction.
Current edition approved Aug. 1, 2018Dec. 15, 2023. Published August 2018February 2024. Originally approved in 2018. Last previous edition approved in 2018 as
G219DOI: 10.1520/G0219-18. – 18. DOI: 10.1520/G0219-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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G219 − 23
3.1.2.1 Discussion—
Breakaway friction coefficient is synonymous with static coefficient of friction.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 inclined plane device, n—mechanism with a flat horizontal surface to be made of or covered with a material of interest on
which a second member made of a material of interest can be placed and the mechanism is then actuated such that the horizontal
plane is increasingly angled with respect to its original horizontal position until motion is produced on the member placed on the
raising plane.
3.2.1.1 Discussion—
The device allows for the continuous measurement of the angle of inclination and the angle at which motion of the rider
commences.
3.2.2 rider, n—body to be placed on the inclined plane.
4. Summary of Guide
4.1 The technique of placing an object on a flat and horizontal “plane” such as a piece of sheet metal and raising one end of the
sheet until the body placed on the sheet starts to slide has been used for centuries to compare the ease with which different objects
or materials slide on each other. Quantitative comparison of various couples can be made by measuring the angle at which the body
placed on the plane starts to slide. The angle at which motion commences is the test metric. The test couple is the plane surface
and the surface that contacts the plane. For example, if a shoe is placed on a flooring sample on the inclined plane, the test couple
is the shoe sole versus the type of flooring. Different shoe bottoms can be compared for their ability to slip on a particular flooring.
The materials of construction as well as the nature of the contacting surfaces determine the breakaway angle. When ranking, for
example, different shoe soles on a particular flooring, the shoes are weighted so that they are all the same weight when compared
for ease of sliding on the flooring of interest.
4.2 The tangent of the breakaway angle becomes the final test metric. This converts the breakaway angle to a dimensionless
number: the static coefficient of friction.
5. Significance and Use
5.1 Guide G115 lists a number of ASTM International standards that use the inclined plane test rig to measure the static coefficient
of specific tribosystems. This guide applies to any material couple that can be made into test specimens that can be made into a
rider on specimens; one being in the form of a rider and the other a plane that can be angled to produce motion of the bodyrider
on the plane. Footwear on walkway surfaces is an example of a very important application. Flooring surfaces that are slippery to
various types of footwear can produce accidents and testing should be done on candidate flooring surfaces and candidate shoe soles
and heels to quantify their relative slip resistance. This guide shows how an inclined plane can be used to make such a comparison.
5.2 The inclined plane method is also very useful in machine design in which parts of components shall slide unassisted down
chutes and the like. An inclined plane test can be used to determine the chute angle that is needed to allow motion on all parts that
are placed on the chute. The applications are numerous.
6. Apparatus
6.1 Fig. 1 is a schematic illustration of the set up and Appendix X1 shows a typical inclined plane device being used to compare
shoe soles on prefinished oak flooring (see Fig. X1.1).
6.2 Any apparatus can be used for this test if it can progressively tilt the plane to produce motion of the rider. The device in Fig.
X1.1 is an electronic protractor that automatically measures the angle of one between the raised leg of the protractor.protractor and
the horizontal plane.
6.3 The simplest mechanism for performing this test is to use a hinge as the pivot for the raising plane and a protractor can be
used to measure that angle that the hinged plane makes with the horizonta
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