ASTM G143-96
(Test Method)Standard Test Method for Measurement of Web/Roller Friction Characteristics
Standard Test Method for Measurement of Web/Roller Friction Characteristics
SCOPE
1.1 This test method can be used to simulate a roller/web transport tribosystem and to measure the static and kinetic coefficient of friction of the web/roller couple when sliding occurs between the two. the objective of this test method is to provide users with the web/roller friction information that can be used for process control, design calculations, and for any other function where web/roller friction needs to ne known.
1.2 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: G 143 – 96
Standard Test Method for
Measurement of Web/Roller Friction Characteristics
This standard is issued under the fixed designation G 143; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method can be used to simulate a roller/web 3.1 Definitions:
transport tribosystem and to measure the static and kinetic 3.1.1 block, v—in plastics, the tendency for one plastic
coefficient of friction of the web/roller couple when sliding surface to adhere to another surface (usually another plastic)
occurs between the two. The objective of this test method is to after being in intimate contact for some residence time.
provide users with web/roller friction information that can be Sometimes it takes hours, sometimes months.
used for process control, design calculations, and for any other 3.1.2 coeffıcient of friction, μ, n—in tribology—the dimen-
function where web/roller friction needs to be known. sionless ratio of the friction force (F) between two bodies to the
1.2 This standard does not purport to address all of the normal force (N) pressing these bodies together.
safety concerns, if any, associated with its use. It is the 3.1.3 friction force, n—the resisting force tangential to the
responsibility of the user of this standard to establish appro- interface between two bodies when, under the action of
priate safety and health practices and determine the applica- external force, one body moves or tends to move relative to the
bility of regulatory limitations prior to use. other.
3.1.4 kinetic coeffıcient of friction, n—the coefficient of
2. Referenced Documents
friction under conditions of macroscopic relative motion be-
2.1 ASTM Standards:
tween two bodies.
D 1894 Test Method for Static and Kinetic Coefficients of 3.1.5 stick-slip, n—a cyclic fluctuation in the magnitudes of
Friction of Plastic Film and Sheeting
friction force and relative velocity between two elements in
D 3108 Test Method for Coefficient of Friction, Yarn to sliding contact, usually associated with a relaxation oscillation
Metal
dependent on elasticity in the tribosystem and on a decrease of
E 8 Test Methods for Tension Testing of Metallic Materials the coefficient of friction with onset of sliding or with increase
E 122 Practice for Choice of Sample Size to Estimate a
of sliding velocity.
Measure of Quality for a Lot or Process 3.1.5.1 Discussion—Classical or true stick-slip, in which
E 177 Practice for Use of the Terms Precision and Bias in
each cycle consists of a stage of actual stick followed by a
ASTM Test Methods stage of overshoot slip, requires that the kinetic coefficient is
E 691 Practice for Conducting an Interlaboratory Study to
lower than the static coefficient. A modified form of relaxation
Determine the Precision of a Test Method
oscillation, with near-harmonic fluctuation in motion, can
G 40 Terminology Relating to Erosion and Wear occur when the kinetic coefficient of friction decreases gradu-
G 115 Guide for Measuring and Reporting Friction Coeffi-
ally with increasing velocity within a certain velocity range. A
cients third type of stick-slip can be due to spatial periodicity of the
G 117 Guide for Calculating and Reporting Measures of
friction coefficient along the path of contact. Random varia-
Precision Using Data from Interlaboratory Wear or Ero- tions in friction force measurement do not constitute stick-slip.
sion Tests
3.1.6 triboelement, n—one of two or more solid bodies
which comprise a sliding, rolling, or abrasive contact, or a
body subjected to impingement or cavitation.
This test method is under the jurisdiction of ASTM Committee G-2 on Wear
3.1.6.1 Discussion—Contacting triboelements may be in
and Erosion and is the direct responsibility of Subcommittee G02.50 on Erosion.
direct contact, or may be separated by an intervening lubricant,
Current edition approved Oct. 10, 1996. Published December 1996.
Annual Book of ASTM Standards, Vol 08.01. oxide, or other film that affects tribological interactions be-
Annual Book of ASTM Standards, Vol 07.01.
tween them.
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 14.02.
Annual Book of ASTM Standards, Vol 03.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
G143–96
3.1.7 tribosystem, n—any system that contains one or more
triboelements, including all mechanical, chemical, and envi-
ronmental factors relevant to tribological behavior.
4. Summary of Test Method
4.1 This test method can be used to measure the friction
characteristics of a flexible web as it slides on a cylindrical
surface. The web conforms to the cylindrical surface in the area
of wrap.
4.2 The test method is conducted on a narrow strip taken
from a web of interest. One end of the strip is draped over a
stationary cylinder and the other end is affixed to a force
measuring device. A mass is applied to the free end of the strip
and the strip is pulled by a mechanism that moves the force
transducer perpendicular to the long axis of the cylindrical
surface. The force encountered in pulling the strip in contact
FIG. 1 Schematic of Capstan Friction Test
with the cylinder (roller) is continuously measured and re-
corded. The static and kinetic coefficients of friction are
calculated from the force measured by the force transducer.
5. Significance and Use
5.1 This test method is intended to simulate the slip of a
flexible web on a roller in a machine or tribosystem that
conveys web materials. Flexible webs such as plastic sheeting,
paper, elastomers, metal foils, and cloth are often transported in
manufacturing processes by combinations of driving and idler
rollers. The friction characteristics of the web/roller interface
often affects the web transport process. If the web/roller
friction is too low, the web can slip on the rollers and be
damaged or damage the roller. High friction on the other hand,
can lead to steering problems and overloading of driving
motors.
5.2 This test method can be used to rank rollers for their
ability to resist slip versus a particular web material (high
friction). Conversely this test method can assess web materials
or web surface coatings such as waxes and lubricants. In this
latter case, the goal may be a low-friction product made from
FIG. 2 Use of Tensile Test Machine to Perform the Capstan
a web (film, magnetic media, paper, and so forth).
Friction Test
5.3 If a tribosystem involves transport of a flexible web on
a roller, this is an appropriate test to use to measure the friction
characteristics of the roller/web couple.
6.2.1 Force transducers shall be accurate within 1 % of the
rated scale of the device and should have overload protection.
6. Apparatus
The friction force during the entire test should be recorded.
6.1 Two possible configurations of the test are shown in
NOTE 1—Caution: Digital filters can alter the force data to the point
Figs. 1 and 2. The essential features of the apparatus are:
where the data are not valid. Analog strip chart recorders have been shown
6.1.1 A force measuring device attached to one member of
to be acceptable recording devices for this test method.
the friction couple.
6.1.2 A stationary cylindrical surface to be used as one 6.3 Cylindrical Surface—The recommended diameter of the
member of the friction couple, test cylinder should be the same diameter as the rollers or
6.1.3 A system to move the flexible strip (web) member of curved surface that is simulated in the friction test. The
the friction couple, and cylinder surface texture and material of construction should be
6.1.4 Masses to be used to tension the free end of the test the same as the tribosystem of interest. If materials are being
strip. evaluated without simulating a particular tribosystem, the test
6.2 Force Measurement—Commercially available or home- roller can be the same as the roller used in the interlaboratory
made strain gage or similar force transducers are acceptable. tests of this test method: 100-mm diameter (100 mm long),
The device should be linear in the force range anticipated in 50-μm thick hard coated (thick hard anodize) 6061-T6 alumi-
testing and the transducer shall be calibrated with known num with a surface roughness of 0.75 to 1 μm Ra (measured
masses or a similar system for each use. parallel to the cylinder’s axis; surface was lathe generated).
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
G143–96
6.4 Sliding Motion—The device shown schematically in 7.1.2 Do not clean the web specimen unless that is part of
Fig. 1 uses a linear motor as the device to pull the test strip. The
the study. If paper or plastic sheets are being tested, they should
cylinder is stationary. Any device with controlled acceleration
be tested with untouched as-manufactured surfaces. Cut the
and velocity is acceptable. A ball screw driven by a variable
web specimen in such a fashion that there is no edge burr on
speed motor is suitable as is the crosshead on a tensile testing
the side that contacts the roller. This is extremely important.
machine. In the latter case, it may be necessary to use a sheave
Ensure that the edges of the strip are parallel and in the desired
with a free-wheeling rolling element bearing to transfer the
orientation with respect to the long axis of the host web. A
motion from a vertical to horizontal plane (see Fig. 2).
useful tool for sample preparation is to affix two single-edged
razor blades to a block of wood spaced at the desired strip
NOTE 2—Some devices rotate the cylinder and hold the web with a
force transducer. This was done in interlaboratory tests and produced the
width. This device can be used to cut samples from thin plastic,
same results as pulling the web over a stationary cylinder.
cloth, and paper webs. The interlaboratory tests were con-
ducted with web strips that were 25 mm in width and 500 mm
6.5 Tensioning Mass—Ordinary masses from balances and
similar laboratory equipment are suitable for tensioning. It is long.
imperative to attach the masses and the friction transducers
7.2 Mounting the Specimen—Affix one end of the web strip
with a device that prevents lateral motion of the test strip.
to the swivel end of the force transducer; drape the strip over
Swivel devices such as the one shown in Fig. 3 allow a straight
the test roller (cylindrical surface), and apply the desired
pull of the test strip. If lateral slip occurs in a particular test, the
tensioning mass. Avoid clamp systems that have significant
results will probably be different from a test in which this
elasticity. If a tension machine is used to produce motion,
unwanted slip does not occur.
flexible steel cable can be used to pull the strip. Ensure that the
6.6 Test Environment—The friction characteristics of some
strip is pulled straight (aligned with the web tension) within6
web/roller couples can be affected by the ambient temperature
1 mm. Markers can be used on the test roller to determine if
and relative humidity. Both friction and temperature at the time
tracking is within the 1-mm limit.
of testing shall be recorded and, if the tribosystem that is to be
7.3 Setting the Sliding Parameters:
simulated involves some special environment, then this should
7.3.1 Velocity—The capstan friction tester allows selection
be simulated. Test samples should be incubated for an adequate
time to reach equilibrium in the intended test environment prior of sliding velocity, sliding distance, and free-end tension on the
to testing. Twenty four hours is a minimum incubation period. strip. It is recommended that values for these parameters be
6.7 Calibration—A suitable system for calibration of the selected to simulate the system of interest. The sliding velocity
force transducer is to mount the transducer vertically and between webs and transport or drive rollers in manufacturing
simply apply a series of known weights on the transducer with
machines is usually in the range from a fraction of a percent of
the force recording device running. Make sure that the output
the web speed to a worst case of 10 % of the web speed. (For
of the force transducer is linearly proportional to the applied
example, if a web conveyance system is being simulated with
force over the range of forces to be measured. Calibrate using
a web speed of 1 m/s, a low-end test velocity may be 5 mm/s
weights that produce force comparable in magnitude to the
and the high-end test velocity 0.1 m/s.) There is a velocity limit
forces anticipated in the friction test.
in this type of test. High speed will cause instability in the
contact of the web with the conforming cylindrical surface.
7. Test Procedure
Users can test the velocity limits of their system, but 0.1 m/s is
7.1 Specimen Preparation:
about the limit of the systems that were used in interlaboratory
7.1.1 Clean the roller surface in a manner that is consistent
testing. A continuous loop test (Test Method D 3108) is more
with the application that is under simulation. Cut virgin strips
appropriate for high sliding velocities.
from the test web as the other friction member. Take care not
7.3.2 Sliding Distance—If the goal of this test method is the
to fingerprint or alter the test surface in handling the web.
static coefficient of friction, the test can be stopped after a few
Convenient sample dimensions are 25 mm wide with a length
millimetres of sliding. If the goal of this test method is both the
of about 500 mm. Practice E 122 or other statistical methods
static and the kinetic coefficients of friction, it is desirable to
can be used to determine the necessary number of test
slide for as long a distance as the test setup will allow. With the
replicates. Three is the minimum.
test setup shown in Fig. 1, the maximum travel on commercial
linear motors is about 0.5 m. The allowable motion on the
pulling device is the limiting factor on sliding distance.
Interlaboratory tests were conducted with a sliding distance of
150 mm. This is the recommended sliding distance for this test.
7.3.3 Test Tension—The tensioning mass affixed to the free
end of the strip specimen can be any magnitude that will
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