ASTM G143-03(2004)
(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
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.
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).
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 the standard. The values given in parentheses are for information only.
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 2004)
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 G 115 Guide for Measuring and Reporting Friction Coeffi-
cients
1.1 This test method covers the simulation of a roller/web
G 117 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
G 163 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 the
3.1.1 blocking, n—unintentional adhesion between plastic
standard. The values given in parentheses are for information
films or between a film and another surface. D883
only.
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-
3.1.3 friction force, n—the resisting force tangential to the
priate safety and health practices and determine the applica-
interface between two bodies when, under the action of
bility of regulatory limitations prior to use.
external force, one body moves or tends to move relative to the
2. Referenced Documents other. G40
3.1.4 kinetic coeffıcient of friction, n—the coefficient of
2.1 ASTM Standards:
friction under conditions of macroscopic relative motion be-
D 883 Terminology Relating to Plastics
tween two bodies. G40
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
Solid Material
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, With
of sliding velocity. G40
a Specified Tolerable Error, the Average for Characteristic
3.1.5.1 Discussion—Classical or true stick-slip, in which
of a Lot or Process
each cycle consists of a stage of actual stick followed by a
E 177 Practice for Use of the Terms Precision and Bias in
stage of overshoot slip, requires that the kinetic coefficient is
ASTM Test Methods
lower than the static coefficient.Amodified form of relaxation
E 691 Practice for Conducting an Interlaboratory Study to
oscillation, with near-harmonic fluctuation in motion, can
Determine the Precision of a Test Method
occur when the kinetic coefficient of friction decreases gradu-
G 40 Terminology Relating to Wear and Erosion
ally with increasing velocity within a certain velocity range.A
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
friction coefficient along the path of contact. Random varia-
and Erosion and is the direct responsibility of Subcommittee G02.50 on Friction.
tions in friction force measurement do not constitute stick-slip.
Current edition approved Nov 1, 2004. Published November 2004. Originally
3.1.6 triboelement, n—one of two or more solid bodies
approved in 1996. Last previous edition approved in 2003 as G 143 – 03.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G143–03 (2004)
3.1.6.1 Discussion—Contacting triboelements may be in
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
friction). Conversely this test method can assess web materials
Friction Test
or web surface coatings such as waxes and lubricants. In this
latter case, the goal may be a low-friction product made from
The device should be linear in the force range anticipated in
a web (film, magnetic media, paper, and so forth).
testing and the transducer shall be calibrated with known
5.3 If a tribosystem involves transport of a flexible web on
masses or a similar system for each use.
a roller, this is an appropriate test to use to measure the friction
6.2.1 Force transducers shall be accurate within 1 % of the
characteristics of the roller/web couple.
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 (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 G 163 for details on digital data acquisi-
6.1.2 A stationary cylindrical surface to be used as one tion))
member of the friction couple, 6.3 Cylindrical Surface—Therecommendeddiameterofthe
6.1.3 A system to move the flexible strip (web) member of test cylinder should be the same diameter as the rollers or
the friction couple, and curved surface that is simulated in the friction test. The
6.1.4 Masses to be used to tension the free end of the test cylinder surface texture and material of construction should be
strip. the same as the tribosystem of interest. If materials are being
6.2 Force Measurement—Commercially available or home- evaluated without simulating a particular tribosystem, the test
made strain gage or similar force transducers are acceptable. roller can be the same as the roller used in the interlaboratory
G143–03 (2004)
tests of this test method: 100-mm diameter (100 mm long), to fingerprint or alter the test surface in handling the web.
50-µm thick hard coated (thick hard anodize) 6061-T6 alumi- Convenient sample dimensions are 25 mm wide with a length
num with a surface roughness of 0.75 to 1 µm Ra (measured of about 500 mm. Practice E 122 or other statistical methods
parallel to the cylinder’s axis; surface was lathe generated). can be used to determine the necessary number of test
6.4 Sliding Motion—The device shown schematically in replicates. Three is the minimum.
Fig. 1 uses a linear motor to pull the test strip. The cylinder is
7.1.2 Do not clean the web specimen unless that is part of
stationary. Any device with controlled acceleration and veloc-
thestudy.Ifpaperorplasticsheetsarebeingtested,theyshould
ity is acceptable.Aball screw driven by a variable speed motor
be tested with untouched as-manufactured surfaces. Cut the
is suitable as is the crosshead on a tensile testing machine. In
web specimen in such a fashion that there is no edge burr on
the latter case, it may be necessary to use a sheave with a
the side that contacts the roller. This is extremely important.
free-wheeling rolling element bearing to transfer the motion
Ensure that the edges of the strip are parallel and in the desired
from a vertical to horizontal plane (see Fig. 2).
orientation with respect to the long axis of the host web. A
useful tool for sample preparation is to affix two single-edged
NOTE 1—Some devices rotate the cylinder and hold the web with a
razor blades to a block of wood spaced at the desired strip
force transducer. This was done in interlaboratory tests and produced the
same results as pulling the web over a stationary cylinder. width.Thisdevicecanbeusedtocutsamplesfromthinplastic,
cloth, and paper webs. The interlaboratory tests were con-
6.5 Tensioning Mass—Ordinary masses from balances and
ducted with web strips that were 25 mm in width and 500 mm
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.
tothebridleendoftheforcetransducer;drapethestripoverthe
Bridle devices such as the one shown in Fig. 3 allow a straight
test roller (cylindrical surface), and apply the desired tension-
pulloftheteststrip.Iflateralslipoccursinaparticulartest,the
ing mass.Avoid clamp systems that have significant elasticity.
results will probably be different from a test in which this
If a tensile-testing machine is used to produce motion, flexible
unwanted slip does not occur.
steel cable can be used to pull the strip. Ensure that the strip is
6.6 Test Environment—The friction characteristics of some
pulled straight (aligned with the web tension) within 61 mm.
web/roller couples can be affected by the ambient temperature
Markers can be used on the test roller to determine if tracking
andrelativehumidity.Bothfrictionandtemperatureatthetime
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
besimulated.Testsamplesshouldbeincubatedforanadequate
7.3.1 Velocity—The capstan friction tester allows selection
timetoreachequilibriumintheintendedtestenvironmentprior ofslidingvelocity,slidingdistance,andfree-endtensiononthe
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
andthehigh-endtestvelocity0.1m/s.)Thereisavelocitylimit
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
about the limit of the systems that were used in interlaboratory
7.1 Specimen Preparation:
7.1.1 Clean the roller surface in a manner that is consistent testing. A continuous loop test (Test Method D 3108) is more
appropriate for high sliding velocities.
with the application that is under simulation. Cut virgin strips
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
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
pulling device is the limiting factor on sliding distance.
Interlaboratory tests were conducted with a sliding distance of
150mm.Thisistherecommendedslidingdistanceforthistest.
7.3.3 Test Tension—The tensioning mass affixed to the free
end of the strip specimen can be any magnitude that will
simulate the system of interest. The practical limit is the
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