Designation:D3702−94(Reapproved2009)
Standard Test Method for
Wear Rate and Coefficient of Friction of Materials in Self-Lubricated Rubbing Contact Using a Thrust Washer Testing Machine1
This standard is issued under thefixed designation D3702;the number immediately following the designation indicates the year of original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
1.Scope
1.1This test method covers the determination of wear rate and coefficient of friction for lf-lubricated materials in rubbing contact by a testing machine2that utilizes a thrust washer specimen configuration.
N OTE1—This machine may also be ud to measure coefficient of friction.
1.2The values in SI units are to be regarded as the standard. In cas where materials,products,or equipment are available only in inch-pound units,SI values in parenthes are for information only.
1.3This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.
2.Terminology
2.1Definitions:
2.1.1coeffıcient of friction,µor f—in tribology—the dimen-sionless ratio of the friction force(F)between two bodies to the normal force(N)pressing the bodies together.
µor f5~F/N!(1) 2.1.1.1Discussion—A distinction is often made between static coefficient of friction and kinetic coefficient of friction.
2.1.2wear—damage to a solid surface,generally involving progressive loss of material,due to relative motion between that surface and a contacting substance or substances.
2.1.3wear rate—the rate of material removal or dimen-sional change due to wear per unit of exposure parameter;for example,quantity of material removed(mass,volume,thick-ness)in unit distance of sliding or unit time.
2.2Definitions of Terms Specific to This Standard:
2.2.1torque—reaction of a tendency to turn due to friction forces between specimens traveling in a circular path.It is the product of a restraining force and the radius at which it acts to balance the frictional torque.
3.Summary of Test Method
3.1The test machine is operated with a test specimen rotating under load against a stationary steel washer.Each test consists of break-in for40h followed by a lected test duration,each at the same s
elected normal load and speed. Load is obtained by application of dead weights to the10:1 lever arm.The contact area is1.29cm2(0.20in.2).The mean rubbing velocity is related to spindle rotational speed:1 rpm=0.0848m/min(0.278ft/min).
3.2The thickness change of the test specimen and torque during test are measured for each test.
3.3Wear rate in centimetres per hour(inches per hour)and coefficient of friction is reported.
4.Significance and U
4.1This test method is ud to determine the equilibrium rate of wear and coefficient of friction of materials in rubbing contact under uful operating conditions,that is,combinations of pressure and velocity that fall below the PV(pres-sure×velocity)limit of the test material.The ur of this test method should determine to his own satisfaction whether the results of this test procedure correlate withfield performance or other bench test machines.If the test conditions are changed, the wear rates may change and the relative value of one material with respect to another may also change.
4.2Test conditions may be lected from Table1.
4.3The precision of wear measurement is relatively inde-pendent of test duration or amount of wear,
but the precision of wear rate(calculation)improves with test duration and amount of wear.It is generally believed that uful wear rate precision
1This test method is under the jurisdiction of ASTM Committee D02on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.L0.05on Solid Lubricants.
Current edition approved Oct.1,2009.Published November2009.Originally
approved in1978.Last previous edition approved in2004as D3702–94(2004).
DOI:10.1520/D3702-94R09.
2An example known to the committee at this time is the Falex Multispecimen
Test Machine,available from Falex Corp.,1020Airpark Drive,Sugar Grove,IL
60554.This manufacturer recommends a maximum test load of808lb(367kg).If
you are aware of alternative suppliers,plea provide this information to ASTM
International Headquarters.Your comments will receive careful consideration at a
meeting of the responsible technical committee,1which you may attend.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959.United States
requires the lection of a test duration sufficient to produce 0.1mm (0.004in.)of wear.Test durations will often be in the 50to 4000-h range.5.Apparatus
5.1Falex Multispecimen Test Machine,Fig.1,shown sche-matically in Fig.2and described in Annex A1.5.2Test Specimen or Rotating Wafer,shown in Fig.3.5.3Stationary Washer,AISI C-1018steel,shown in Fig.4.The surface finish should be 1662µin.AA,the hardness Rc 2065.
5.4Micrometer (Note 4),capable of measuring to the nearest 0.003mm (0.0001in.).
6.Reagents and Materials
6.1Solvent,safe,non-film forming,nonchlorinated.
N OTE 2—Petroleum distillates,formerly ud as solvents,have been eliminated due to possible toxic effects.Each ur should lect a solvent that can meet applicable safety requirements and thoroughly clean machine parts.
6.2Appropriate reagents for cleaning the test specimen as recommended by the manufacturer of the test material.
7.Preparation of Apparatus
7.1Measure the finish of the steel mating surface perpen-dicular to the finishing direction.
7.2Before each test,thoroughly clean the steel washer and both specimen holders using the solvent per 5.1.
N OTE 3—Remove all solvents from the washer before testing.
7.3Clean the test specimen as recommended by the manu-facturer of the test material.
7.3.1Store cleaned test specimens prior to testing in a glass jar.
7.3.2Following the cleaning,do not handle the test speci-mens with bare hands.It is recommended that clean cotton gloves or clean tweezers or tongs be ud.
N OTE 4—Check compatibility of the test specimen cleaning procedure and reagents with the specific material to be tested.
7.4Pret the speed control to provide the desired speed as measured in revolutions per minute using the built-in tachom-eter.Refer to Table 1to convert the specified velocity to revolutions per minute.
7.5Install the test specimen in the upper specimen holder with the bolt and washer provided.Torque the bolt to
TABLE 1Test Conditions A
Rotational
speed,rpm
Rubbing Velocity,ft/min (m/min)Load,lb (kg),to Obtain PV ,psi ×ft/min (kg/cm 2×m/min)at Selected Speeds
PV 11250(26.8)
PV 22500(53.6)PV 35000(107.1)PV 410000(214.3)3610(3.05)25.0(11.3)50.0(22.7)100(45.4)200(90.7)18050(15.2) 5.0(2.3)10.0(4.5)20.0(9.1)40.0(18.1)900
250(76.2)
1.0(0.5)
2.0(0.9) 4.0(1.8)8.0(
3.6)
A
For many applications a wear rate exceeding 1.0×10−5in./h (2.5×10−7m/h)is considered excessive.Typical wear rates for some commonly ud materials at different PV levels are:
Acetal homopolymer at PV 1:5×10−6to 1×10−5in./h (1.3×10−7to 2.5×10−7m/h)Acetal homopolymer at PV 2:
1×10−5to 3×10−5in./h (2.5×10−7to 7.5×10−7m/h)22%PTFE-filled acetal homopolymer at PV 2:3×10−6to 6×10−6in./h (7.5×10−8to 1.5×10−7m/h)Polyamide (Type 6-6)at PV 2:
1×10−5to 5×10−5in./h (2.5×10−7to 1.3×10−6m/h)15%graphite filled polyimide restin at PV 3:
1×10−
5
to 2×10−5in./h (2.5×10
−7to 5×10−7m/h)
FIG.1The Falex Multispecimen Test Machine
2.860.6J ~2565in.·lbf !(2)
7.6Place the steel washer in the lower specimen holder.7.7Balance the load lever arm with the bale rod attached.7.8Mount the test specimen together with its specimen holder in the rotary spindle so that the drive pins of the spindle
are inrted in the drive pin holes of the specimen holder and the specimen holder is free to pivot on the ball at.7.9Determine the dead weight,w ,to be applied to the bale rod as
follows:
FIG.2Thrust Washer Test Specimen
Arrangement
FIG.3Rotating Test
Specimen
W 5
F 10
(3)
where:
F =normal force.
7.10If coefficient of friction is to be determined,check calibration of torque meter and adjust,if required,according to equipment manufacturer’s instructions.
N OTE 5—Calibrate torque meter such that the anticipated test torque is approximately two-thirds of calibration value.
N OTE 6—A chart recorder can be ud to continuously record torque throughout the test.Zero and span the recorder according to the manu-facturer’s instructions.
8.Procedure
8.1With the specimens and bale rod in position,gently apply the appropriate weight to the bale rod.8.2Turn on the machine.
8.3When the prescribed break-in interval duration (40h)has been completed,stop the machine,remove the weights from the bale rod and carefully lower the stationary specimen holder to its lowest position.
8.4Remove the test specimen together with its specimen holder and clean with a lint-free wiper.
8.5Condition the specimens for a minimum of 1h at room temperature prior to measuring thickness.
8.6Measure the thickness of the test specimen together with its specimen holder at four places,90°a
part.Mark the test specimen (inside the raid test surface)so subquent mea-surements can be made at the same places.
8.7Balance the load lever arm with the bale rod attached.8.8Mount the test specimen together with its specimen holder in the rotary spindle so that the drive pins of the spindle are inrted in the drive pin holes of the specimen holder and the specimen holder is free to pivot on the ball at.8.9With the specimens and bale rod in position,gently apply the appropriate weight to the bale rod.
8.10Turn on the machine and chart recorder if torque is to be recorded.
8.11When the prescribed test interval duration has been completed,stop the machine,remove the weights from the bale rod,and carefully lower the stationary specimen holder to its lowest position.
8.12Remove the test specimen together with its specimen holder and clean with a lint-free wiper.
8.13Condition the specimens for a minimum of 1h at room temperature prior to measuring thickness.
8.14Measure the thickness of the test specimen together with its specimen holder at the same four places,90°apart,previously
marked.
FIG.4Stationary Steel Washer
Specimen
9.Calculation
9.1Wear:
9.1.1Record the (four)thickness measurements for the test specimen before and after test,and actual test duration in hours.
9.1.2Calculate the wear rate as follows:
WR 5
~X 1a 1X 1b 1X 1c 1X 1d !2~X 2a 1X 2b 1X 2c 1X 2d !
4T
(4)
where:
WR =wear rate,in./h (m/h),X =thickness,in.,(m),and T =test duration,h.
9.1.3Subscripts 1a ,1b ,1c ,and 1d are the initial four thickness measurements taken 90°apart on the upper rotating specimen.Subscripts 2a ,2b ,2c ,and 2d are the corresponding final thickness measurements.
9.2Coeffıcient of Friction:
9.2.1Calculate the coefficient of friction from the torque values as follows:
f 5T /rW
(5)
where:f =coefficient of friction,
T =specimen torque,N·m (lb·in.),
r =test specimen radius,13.49mm (0.531in.),and W =normal force,kg (lb).10.Precision and Bias
10.1Precision—The precision 3of this test method for wear as determined by the statistical examination of interlaboratory test results is as follows:
10.1.1Repeatability—The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would,in the long run,in the normal and correct operation of the test method exceed the following values only in one ca in twenty.
0.019mm ~0.00075in.!
(6)
10.1.2Reproducibility—The difference between two single and independent results obtained by different operators work-ing in different laboratories on identical test material would,in the long run,exceed the following values only in one ca in twenty.
0.030mm ~0.00118in.!
(7)
10.2The tests on which the precision statement is bad were all conducted at PV 3,with 180rpm ud in round robin 1,2a,and 3,and 720rpm in round robin 2b.Test durations were 100h,except for round robin 1where they ranged from 118to 313h.Wear in 100h round robins averaged 0.00027to 0.00049in.,and in no test did wear exceed 0.0017in.10.3Bias—Since there is no accepted reference material suitable for determining the bias for the procedure for measur-ing wear rate,bias has not been determined.11.Keywords
11.1coefficient of friction;lf-lubricated;torque;wear;wear-rate
ANNEX
(Mandatory Information)
A1.DESCRIPTION OF THE THRUST WASHER TESTING MACHINE (Fig.1)
A1.1Dead weights are attached to a bale rod,and act through a 10:1lever arm to load the stationary (lower)washer axially upward against a rotating (upper)test specimen.The lever arm may be balanced to compensate for the weight of the stationary washer.Optional controlled pneumatic loading sys-tems are available to replace applications of dead weight.A1.2The rotary spindle is driven by a variable-speed dc motor with feed back speed control,controlled by a 10-turn potentiometer,acting through dual-range step pulleys.Typical spindle speed range is 10to 7200rpm.A built-in tachometer
provides speed indication.An elapd time indicator with ret feature to indicate motor running time should be included.A1.3In rotation at motion,torque is indicated throughout the test by a digital indicator.
A1.4Optional features include an assortment of torque measurement devices;apparatus for the application,control,and readout of various test environment conditions;and devices to accommodate alternative test sample configurations.
3
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Rearch Report
RR:D02-1054.
