ASTM G143-03(2013)
(Test Method)Standard Test Method for Measurement of Web/Roller Friction Characteristics
Standard Test Method for Measurement of Web/Roller Friction Characteristics
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 a web (film, magnetic media, paper, and so forth).
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.
SCOPE
1.1 This test method covers the simulation of a roller/web transport tribosystem and the measurement of 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 web/roller friction information that can be used for process control, design calculations, and for any other function where web/roller friction needs to be known.
1.2 The values stated in SI units are to be regarded as 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: G143 − 03 (Reapproved 2013)
Standard Test Method for
Measurement of Web/Roller Friction Characteristics
This standard is issued under the fixed designation G143; 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 G115 Guide for Measuring and Reporting Friction Coeffi-
cients
1.1 This test method covers the simulation of a roller/web
G117 Guide for Calculating and Reporting Measures of
transport tribosystem and the measurement of the static and
Precision Using Data from Interlaboratory Wear or Ero-
kinetic coefficient of friction of the web/roller couple when
sion Tests
sliding occurs between the two. The objective of this test
G163 Guide for Digital Data Acquisition in Wear and
method is to provide users with web/roller friction information
Friction Measurements
that can be used for process control, design calculations, and
for any other function where web/roller friction needs to be
3. Terminology
known.
3.1 Definitions of Terms Specific to This Standard:
1.2 The values stated in SI units are to be regarded as
3.1.1 blocking, n—unintentional adhesion between plastic
standard. No other units of measurement are included in this
films or between a film and another surface. D883
standard.
3.1.2 coeffıcient of friction, µ, n—in tribology—the dimen-
1.3 This standard does not purport to address all of the
sionlessratioofthefrictionforce(F)betweentwobodiestothe
safety concerns, if any, associated with its use. It is the
normal force (N) pressing these bodies together. G40
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.1.3 friction force, n—the resisting force tangential to the
bility of regulatory limitations prior to use.
interface between two bodies when, under the action of
external force, one body moves or tends to move relative to the
2. Referenced Documents
other. G40
2.1 ASTM Standards:
3.1.4 kinetic coeffıcient of friction, n—the coefficient of
D883 Terminology Relating to Plastics
friction under conditions of macroscopic relative motion be-
D1894 Test Method for Static and Kinetic Coefficients of
tween two bodies. G40
Friction of Plastic Film and Sheeting
3.1.5 stick-slip, n—a cyclic fluctuation in the magnitudes of
D3108 Test Method for Coefficient of Friction,Yarn to Solid
friction force and relative velocity between two elements in
Material
sliding contact, usually associated with a relaxation oscillation
E8 Test Methods for Tension Testing of Metallic Materials
dependent on elasticity in the tribosystem and on a decrease of
E122 Practice for Calculating Sample Size to Estimate,With
the coefficient of friction with onset of sliding or with increase
Specified Precision, the Average for a Characteristic of a
of sliding velocity. G40
Lot or Process
3.1.5.1 Discussion—Classical or true stick-slip, in which
E177 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
E691 Practice for Conducting an Interlaboratory Study to
lower than the static coefficient.Amodified form of relaxation
Determine the Precision of a Test Method
oscillation, with near-harmonic fluctuation in motion, can
G40 Terminology Relating to Wear and Erosion
occur when the kinetic coefficient of friction decreases gradu-
ally with increasing velocity within a certain velocity range.A
1 third type of stick-slip can be due to spatial periodicity of the
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.
friction coefficient along the path of contact. Random varia-
Current edition approved Nov. 15, 2013. Published November 2013. Originally
tions in friction force measurement do not constitute stick-slip.
approved in 1996. Last previous edition approved in 2009 as G143–03(2009). DOI:
10.1520/G0143-03R13.
3.1.6 triboelement, n—one of two or more solid bodies
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
which comprise a sliding, rolling, or abrasive contact, or a
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
body subjected to impingement or cavitation. G40
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.1.6.1 Discussion—Contacting triboelements may be in
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G143 − 03 (2013)
direct contact, or may be separated by an intervening lubricant,
oxide, or other film that affects tribological interactions be-
tween them.
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. G40
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.Thewebconformstothecylindricalsurfaceinthearea
of wrap.
4.2 The test method is conducted on a narrow web or 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
FIG. 1 Schematic of Capstan Friction Test
measuring device.Amass 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
with the stationary cylinder (roller) is continuously measured
and recorded. 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,metalfoils,andclothareoftentransportedin
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
FIG. 2 Use of Tensile Test Machine to Perform the Capstan Fric-
friction). Conversely this test method can assess web materials tion Test
or web surface coatings such as waxes and lubricants. In this
latter case, the goal may be a low-friction product made from
6.2 Force Measurement—Commercially available or home-
a web (film, magnetic media, paper, and so forth).
made strain gage or similar force transducers are acceptable.
5.3 If a tribosystem involves transport of a flexible web on
The device should be linear in the force range anticipated in
a roller, this is an appropriate test to use to measure the friction
testing and the transducer shall be calibrated with known
characteristics of the roller/web couple.
masses or a similar system for each use.
6.2.1 Force transducers shall be accurate within 1 % of the
6. Apparatus
rated scale of the device and should have overload protection.
The friction force during the entire test should be recorded.
6.1 Two possible configurations of the test are shown in
(Warning—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
6.1.1 A force measuring device attached to one member of
been shown to be acceptable recording devices for this test
the friction couple,
method. (See Guide G163 for details on digital data acquisi-
6.1.2 A stationary cylindrical surface to be used as one
tion))
member of the friction couple,
6.1.3 A system to move the flexible strip (web) member of
6.3 Cylindrical Surface—The recommended diameter of the
the friction couple, and test cylinder should be the same diameter as the rollers or
6.1.4 Masses to be used to tension the free end of the test curved surface that is simulated in the friction test. The
strip. cylinder surface texture and material of construction should be
G143 − 03 (2013)
the same as the tribosystem of interest. If materials are being 7. Test Procedure
evaluated without simulating a particular tribosystem, the test
7.1 Specimen Preparation:
roller can be the same as the roller used in the interlaboratory
7.1.1 Clean the roller surface in a manner that is consistent
tests of this test method: 100-mm diameter (100 mm long),
with the application that is under simulation. Cut virgin strips
50-µm thick hard coated (thick hard anodize) 6061-T6 alumi-
from the test web as the other friction member. Take care not
num with a surface roughness of 0.75 to 1 µm Ra (measured
to fingerprint or alter the test surface in handling the web.
parallel to the cylinder’s axis; surface was lathe generated).
Convenient sample dimensions are 25 mm wide with a length
6.4 Sliding Motion—The device shown schematically in
of about 500 mm. Practice E122 or other statistical methods
Fig. 1 uses a linear motor to pull the test strip. The cylinder is
can be used to determine the necessary number of test
stationary. Any device with controlled acceleration and veloc-
replicates. Three is the minimum.
ity is acceptable.Aball screw driven by a variable speed motor
7.1.2 Do not clean the web specimen unless that is part of
is suitable as is the crosshead on a tensile testing machine. In
thestudy.Ifpaperorplasticsheetsarebeingtested,theyshould
the latter case, it may be necessary to use a sheave with a
be tested with untouched as-manufactured surfaces. Cut the
free-wheeling rolling element bearing to transfer the motion
web specimen in such a fashion that there is no edge burr on
from a vertical to horizontal plane (see Fig. 2).
the side that contacts the roller. This is extremely important.
Ensure that the edges of the strip are parallel and in the desired
NOTE 1—Some devices rotate the cylinder and hold the web with a
force transducer. This was done in interlaboratory tests and produced the orientation with respect to the long axis of the host web. A
same results as pulling the web over a stationary cylinder.
useful tool for sample preparation is to affix two single-edged
razor blades to a block of wood spaced at the desired strip
6.5 Tensioning Mass—Ordinary masses from balances and
width.Thisdevicecanbeusedtocutsamplesfromthinplastic,
similar laboratory equipment are suitable for tensioning. It is
cloth, and paper webs. The interlaboratory tests were con-
imperative to attach the masses and the friction transducers
ducted with web strips that were 25 mm in width and 500 mm
with a device that prevents lateral motion of the test strip.
long.
Bridle devices such as the one shown in Fig. 3 allow a straight
pulloftheteststrip.Iflateralslipoccursinaparticulartest,the
7.2 Mounting the Specimen—Affix one end of the web strip
results will probably be different from a test in which this
tothebridleendoftheforcetransducer;drapethestripoverthe
unwanted slip does not occur.
test roller (cylindrical surface), and apply the desired tension-
ing mass.Avoid clamp systems that have significant elasticity.
6.6 Test Environment—The friction characteristics of some
If a tensile-testing machine is used to produce motion, flexible
web/roller couples can be affected by the ambient temperature
steel cable can be used to pull the strip. Ensure that the strip is
andrelativehumidity.Bothfrictionandtemperatureatthetime
pulled straight (aligned with the web tension) within 61 mm.
of testing shall be recorded and, if the tribosystem that is to be
Markers can be used on the test roller to determine if tracking
simulated involves some special environment, then this should
is within the 1-mm limit.
besimulated.Testsamplesshouldbeincubatedforanadequate
timetoreachequilibriumintheintendedtestenvironmentprior
7.3 Setting the Sliding Parameters:
to testing. Twenty four hours is a minimum incubation period.
7.3.1 Velocity—The capstan friction tester allows selection
6.7 Calibration—A suitable system for calibration of the ofslidingvelocity,slidingdistance,andfree-endtensiononthe
force transducer is to mount the transducer vertically and
strip. It is recommended that values for these parameters be
simply apply a series of known weights on the transducer with selected to simulate the system of interest.The sliding velocity
the force recording device running. Make sure that the output
between webs and transport or drive rollers in manufacturing
of the force transducer is linearly proportional to the applied machines is usually in the range from a fraction of a percent of
force over the range of forces to be measured. Calibrate using
the web speed to a worst case of 10 % of the web speed. (For
weights that produce force comparable in magnitude to the example, if a web conveyance system is being simulated with
forces anticipated in the friction test.
a web speed of 1 m/s, a low-end test velocity may be 5 mm/s
andthehigh-endtestvelocity0.1m/s.)Thereisavelocitylimit
in this type of test. High speed will cause instability in the
contact of the web with the conforming cylindrical surface.
Users can test the velocity limits of their system, but 0.1 m/s is
about the limit of the systems that were used in interlaboratory
testing. A continuous loop test (Test Method D3108) is more
appropriate for high sliding velocities.
7.3.2 Sliding Distance—If the goal of this test method is the
static coefficient of friction, the test can be stopped after a few
millimetres of sliding. If the goal of this test method is both the
static and the kinetic coefficients of friction, it is desirable to
slide for as long a distance as the test setup will allow.With the
test setup shown in Fig. 1, the maximum travel on commercial
linear motors is about 0.5 m. The allowable motion on the
FIG. 3 Method for Gripping the Test Strip pulling device is the limiting factor on sliding distance.
G143 − 03 (2013)
Interlaboratory tests were conducted with a sliding distance of
T = force applied to the free end of the web by the hanging
150mm.Thisistherecommendeds
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