ASTM G133-22

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Designation: G133 − 05 (Reapproved 2016) G133 − 22
Standard Test Method for
Linearly Reciprocating Ball-on-Flat Sliding Wear
This standard is issued under the fixed designation G133; 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 test method covers laboratory procedures for determining the sliding wear of ceramics, metals, and other candidate
wear-resistant materials using a linear, reciprocating ball-on-flat plane geometry. The direction of the relative motion between
sliding surfaces reverses in a periodic fashion such that the sliding occurs back and forth and in a straight line. The principal
quantities of interest are the wear volumes of the contacting ball and flat specimen materials; however, the coefficient of kinetic
friction may also be measured using the method described. This test method encompasses both unlubricated and lubricated testing
procedures. The scope of this test method does not include testing in corrosive or chemically aggressive environments.environ-
ments or extremes of temperature and humidity.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.after
SI units are provided for information only and are not considered 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 safety, health, and healthenvironmental 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:
E112 Test Methods for Determining Average Grain Size
E1181 Test Methods for Characterizing Duplex Grain Sizes
G40 Terminology Relating to Wear and Erosion
G99 Test Method for Wear Testing with a Pin-on-Disk Apparatus
G115 Guide for Measuring and Reporting Friction Coefficients
G117 Guide for Calculating and Reporting Measures of Precision Using Data from Interlaboratory Wear or Erosion Tests
(Withdrawn 2016)
G118 Guide for Recommended Format of Wear Test Data Suitable for Databases (Withdrawn 2016)
3. Terminology
3.1 Definitions:
This test method is under the jurisdiction of ASTM Committee G02 on Wear and Erosion and is the direct responsibility of Subcommittee G02.40 on Non-Abrasive Wear.
Current edition approved June 1, 2016Nov. 1, 2022. Published June 2016November 2022. Originally approved in 1995. Last previous edition approved in 20102016 as
G133 – 05 (2010).(2016). DOI: 10.1520/G0133-05R16.10.1520/G0133-22.
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’sstandard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
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G133 − 22
3.1.1 Definitions used in this test method are given in Terminology G40. The following definitions of important terms used in this
test method are cited from Terminology G40.
3.1.2 friction force—force, n—the resisting force tangential to the interface between two bodies when, under the action of an
external force, one body moves or tends to move relative to the other.
3.1.3 Hertzian contact pressure—pressure, n—the magnitude of the pressure at any specified location in a Hertzian contact area,
as calculated from Hertz’sHertz’s equations of elastic deformation.
3.1.4 wear—wear, n—damage to a solid surface, generally involving the progressive loss of material due to relative motion
between that surface and a contacting surface or surfaces.
3.1.5 wear rate—rate, n—the rate of material removal or dimensional change due to wear per unit of exposure parameter, for
example, quantity removed (mass, volume, thickness) in unit distance of sliding or unit time.
4. Summary of Test Method
4.1 This test method involves two specimens—a flat specimen and a spherically ended specimen (herein called the “ball”
specimen) which slides specimen, but the terms “pin” and “.spherical tip” are also acceptable and in common use) that slide
against the flat specimen. These specimens move relative to one another in a linear, back and forth sliding motion, motion (“linearly
reciprocating”), under a prescribed set of conditions.
FIG. 1 Reciprocating Test—Schematic Diagram
4.2 In this test method, the load is applied vertically downward through the ball specimen against the horizontally mounted flat
specimen. The normal load, stroke length, frequency and type of oscillation, test temperature, lubricant (if any), test duration, and
atmospheric environment (including relative humidity range) are selected from one of two procedures.
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4.3 Since this test method involves reciprocating sliding where changes in the sliding velocity and direction of motion occur
during the test, constant velocity conditions are not maintained. The manner in which the velocity varies with time is determined
by the design of the mechanism which drives the ball or flat specimen back and forth.
4.4 Dimensional changes for both ball and flat specimens are used to calculate wear volumes and wear rates.
4.5 Friction forces are can also be measured during the test and may be used to assess changes in the contact conditions or the
kinetic friction coefficient as a function of time.
5. Significance and Use
5.1 This test method is designed to simulate the geometry and motions that are experienced in many types of rubbing components
whose normal operation results in periodic reversals in the direction of relative sliding. The wear resulting from this mode of
movement may differ from that experienced by the same materials sliding continuously in only one direction (unidirectional
sliding) sliding, for example, using Test Method G99) even for comparable durations of contact. Test loads and speeds This is
particularly true for liquid-lubricated tests where the reversal of motion means that the entrainment velocity transitions through
zero but also in unlubricated tests in which stress reversal occurs. The normal load(s) and sliding speed(s) to be used during testing
are to be determined by the severity of the proposed application or purpose of the testing. Either of two sets of testing conditions
(designated Procedures A and B) may be used.
6. Apparatus
6.1 General Description—Fig. 1 shows the arrangement for the reciprocating ball-on-flat wear test available on a commercial
machine. The ball is rigidly mounted and has a spherical tip which moves back and forth across the surface of a polished flat
specimen. Use of a spherical tip ball (that is, a “spherical tip”) alleviates the alignment problems associated with flat-ended
ballspins sliding on flat surfaces. Alternate configurations in which the flat moves and the ball specimen is fixed may be used. A
provision is made for applying a uniform normal force (load) to the contact between the ball and the flat. Temperature measurement
and control capability is provided to heat and monitor the flat specimen which may either be immersed in a lubricant bath or tested
without lubricant. The tangential force can be measured continuously during oscillating contact and used to obtain friction
coefficient data.
6.2 Specimen Drive—A drive train, capable of providing smooth, repeatable, reciprocating motion to the ball and overcoming the
frictional resistance of the specimens at maximum load, is required. For example, a Scotch yoke drive mechanism can provide a
smooth, sinusoidal velocity profile for the ball specimen relative to the flat specimen without the need for the motor to stop and
reverse direction periodically. Stepper-type motors may also be used provided that the motion is smooth and uniform.
6.3 Ball and Ball Specimen Holder—The ball specimen may be a fixed bearing ball or any spherically tipped specimen as long
as the sliding contact is equivalent to a ball on a flat plane. If a bearing ball is used, it shall be clamped tightly enough to prevent
slippage during the test. The ball holder should be rigid enough so that the periodic reversal in the sliding direction does not result
in tilting or other misalignment of the contact.
6.4 Flat Specimen Holder—The flat specimen is secured to the base of the machine to prevent slippage or buckling during the test.
A variety of shapes and configurations for the flat specimen are possible. The primary criterion is that the coupon present flat
specimen presents a flat, horizontal surface to the ball specimen.
6.5 Instrumentation:
6.5.1 Friction Force—A tension-compression load cell or similar force-sensing device may be used to measure the friction forces
generated during sliding. Calibration of the friction force (see subsection 7.1.3) in both forward and reverse sliding directions is
required. Since the direction of the friction force changes rapidly during the test, traditional strip-chart-type recorders may be too
slow to follow these changes at high frequencies of reciprocation. A commercial version of this machine is available with a signal
conditioner to rectify, and output the root-mean-square friction force to a strip-chart-recorder or to a computerized data acquisition
Machines of this type are described in A Catalogue of Friction and Wear Devices, American Society of Lubrication Engineers (now STLE) 838 Busse Highway, Park
Ridge, IL, 1973, pp. 50–72.
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system. reciprocation, therefore, modern data acquisition systems capable of sampling frequencies well in excess (an order of
magnitude is suggested) of the reciprocating frequency of the test being conducted are preferred. The method of sensing and
recording friction force during the test shall be described in the testing report.
6.5.2 Test Duration—In this test method, test duration is specified in seconds. To compute the sliding distance in metres or number
of cycles, use the following:
X 5 0.002 3t 3f 3L (1)
or
N 5 t 3f (2)
where:
where:
X = total sliding distance of the ball, m,
N = number of cycles in the test,
t = test time, s,
f = oscillating frequency, Hz (cycles/s), and
L = length of stroke, mm.
A cycle is defined as two stroke lengths (up and back). Electronic Manual, or feedback-controlled, electronic timers can be used
to terminate the test. If a physical, electronic, or software-based, cycle-counter is available, this may be used instead of the timer,
in which case Eq 2 will be used.
6.5.3 Humidity—The wear and friction of many materials is significantly affected by the moisture in the air. It is thereforeis,
therefore, required that the relative humidity (to an accuracy of 63 %) be measured before and during the test. Humidity can vary
with air flow and in different parts of the same room, so the humidity sensor should be located as close to the test specimens as
reasonably possible, in such a way that the air movement conditions are the same for humidity sensor as for the test specimens.
6.5.4 Temperature—The ambient temperature, in degrees Celsius, shall be measured and reported during room temperature tests.
In full immersion, liquid-lubricated tests, the bath temperature shall be measured and reported.measured, with consideration taken
to a uniform temperature distribution being achieved, and reported. For unlubricated tests, use of a thermocouple on the surface
of the specimen, positioned not to impede the reciprocating motion, should be considered.
7. Calibration
7.1 TheThe parts of the apparatus that require calibration are (1) the loading system, (2) the motion drive (speed and stroke
length), and (3) the friction force sensor.
7.1.1 Loading System—The load (normal force) applied to the specimen shall be checked periodically. In machines which apply
the load by a spring/lever arrangement and indicate the load on a dial gage, this can be done by substituting a previously calibrated
compression load cell for the specimen and checking the applied load indicated on the loading dial against the calibrated load cell
output. Statically applied loads shall be kept constant within a maximum deviation of 62.0 % of the test load. For example,
permitted static error of a 25.0-N25.0 N normal force would be 60.5 N. During oscillating tests, the normal force may vary slightly
about the mean value due to the dynamics of the machine. This variation is to be expected.expected and, for unlubricated tests,
it is suggested that sacrificial test specimens are used to conduct a preliminary test in order to assess the magnitude of this variation.
7.1.2 Motion Drive—The oscillating frequency of the moving specimen shall be checked periodically against the drive motor
setting to ensure that the rate of oscillation is known. (Warning—Due to inertial effects, differences in the loading and fixturing
method become more significant as the oscillating frequency of the test is increased, and harmonic frequencies characteristic of
the test machine must be avoided when selecting the oscillating frequency.)
7.1.3 Friction Force Sensor—The friction force sensor shall be calibrated periodically (as advised by the manufacturer, if
available) in both directions of load application. application and with consideration of the temperature(s) at which testing is to be
conducted. Depending on the machine, a fixture whichthat applies a fixed calibrating load in line with the normal point of contact
between the ball and flat should be used.
8. Procedure
8.1 Specimen Preparation—The ball specimen and flat specimen shall be used either in a polished condition, or in a specified
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condition consistent with the application of interest. In a polished condition, the surface should be as free as possible from
preparation artifacts such as grinding-induced cracks, gross grinding marks, and grain pull-out. Surface roughnesses of
0.020.02 μm to 0.05-μm0.05 μm R (arithmetic roughness) are typical.
a
8.2 Clean the specimens using the following procedure:
8.2.1 Wash with a mild liquid laboratory glassware cleaner,
8.2.2 Hot air dry,
8.2.3 Ultrasonically clean in acetone (2 min),
8.2.4 Hot air dry,
8.2.5 Ultrasonically clean in methanol (2 min), and
8.2.6 Hot air dry.
8.2.7 If there is considerable porosity in the specimens, it is necessary that they be baked dry for 4 h at a temperature greater than
150°C150 °C in a clean oven.
NOTE 1—Certain materials could be adversely affected by cleaning in solvents. Similarly, for metal specimens that have significant porosity, such as those
obtained by means of powder metallurgy (sintering) or additive manufacturing processes are likely to be susceptible to considerable oxidation during
baking. Deviations from the prescribed cleaningpreparation procedure are permitted, but they shall be described in the report.
8.3 Clean the specimens after they are secured in place in the test fixture by wiping with acetone and then with
methanol-moistened cotton swabs. It is possible that during mounting, some contamination was inadvertently placed on them, and
this final cleaning will help alleviate the problem. Inspect the ball tipsurface with a hand lens after it is mounted to ensure that there
areis no defectsdamage in the contact area.
8.4 Gently lower the ball specimen upon the flat specimen, and ensure that the reciprocating drive shaft motion is horizontal and
parallel to the surface of the flat specimen. The height of the specimen or mount may require adjustment to ensure that this
condition is fulfilled. Apply the prescribed test load. Confirm that the desired oscillating speed has been set before turning on the
motor.
8.5 Two possible testing procedures, one for unlubricated tests (Procedure A), and one for high-contact stress-lubricated
liquid-lubricated tests at high contact stress and elevated temperature (Procedure B), are given in 8.5.1. The procedure appropriate
for the given materials and test severity should be selected. If neither procedure in 8.5.1 is determined to be suitable, other
conditions may be used, but testing will not be in compliance with this test method. See the reporting requirements in Section 10
for reporting exceptions to Procedures A and B.
8.5.1 The two testing procedures are as follows.
8.5.1.1 Procedure A—Unlubricated wear testing at room temperature.
(1) Pin tip Ball radius, 4.76 mm ( ⁄16 in.),
(2) Normal force, 25.0 N,
(3) Stroke length, 10.0 mm,
(4) Oscillating frequency, 5.0 Hz,
(5) Test duration, 16 min 40 s (sliding distance 100 m),
(6) Ambient temperature, 2222 °C 6 3°C,3 °C,
(7) Relative humidity, 4040 % to 60 %, and
(8) Lubrication, none applied.
8.5.1.2 Procedure B—Lubricated wear testing at elevated temperature.
(1) Pin tip Ball radius, 4.76 mm ( ⁄16 in.),
(2) Normal force, 200.0 N,
(3) Stroke length, 10.0 mm,
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(4) Oscillating frequency, 10.0 Hz,
(5) Test duration, 33 min 20 s (sliding distance 400 m),
(6) Temperature, 150150 °C 6 2°C,2 °C,
(7) Relative humidity, 4040 % to 60 %, and
(8) Lubrication, full immersion under the selected lubricant (see Note 2).
NOTE 2—This procedure requires full-immersion lubrication. If other methods, such a controlled drip feeding system, are used to simulate certain
applications, the provisions of 8.6 will apply.
8.5.2 When heated, liquid-lubricated tests are being conducted, as in Procedure B, apply the lubricant and heat the specimens to
the selected temperature allowing them to equilibrate for not less than 5 min before applying the load and starting the test. Bath
temperature shall be controlled to within a maximum deviation of 62.0°C from the desired temperature. A fresh supply of lubricant
shall be used for each test unless the objective is to evaluate the effects of used lubricants on friction and wear.
8.5.3 Set the timer (or cycle counter), if available, for the selected test duration.
8.5.4 Start the friction (and temperature) recording equipment and initiate the test.
8.5.5 After the prescribed duration, stop the motor. Remove the normal force to recheck the zero point on the friction force
recording system.
8.5.6 Allow specimens to cool, if heated, then remove the test specimens. To measure the wear, it is necessary to clean the
specimens in such a way that the surface features are not altered. For unlubricated tests, debris should be collected or imaged for
analysis, if desired, then a concentrated jet of air may be used to dispel the debris from the worn area of the specimens. For
liquid-lubricated specimens, ultrasonic cleaning in a suitable solvent may be used. Specimens shall be thoroughly dried.
8.5.7 Examine the tip of the ball specimen to ensure that no rolling or other slippage has taken place. Any ball movement within
the holder during the test invalidates the test results. Similarly, any slippage of the flat specimen in its fixture invalidates the test
results.
8.6 Alternative Testing Procedures—To achieve certain simulation conditions, or for other technical reasons, Procedures A and B
may not be suitable for a given reciprocating wear testing project. Modifications to the specific test conditions prescribed in
Procedures A and B may be used for conducting such tests; however, in reporting the results, the specific parameters which are
not in compliance with one of the standard testing procedures shall be specifically noted. A statement such as the following may
then be used: “These tests are not in full compliance with the provisions of Test Method G133, Procedure A, because the normal
force in these tests was 50.0 N, instead of 25.0 N as prescribed by the standard, and the stroke length was 5.0 mm, instead of 10.0
mm as prescribed by the standard. All other provisions of Test Method G133 have been followed.”
9. Measurement and Calculation of Wear
9.1 Depending upon the relative wear of ball and flat specimens, various assumptions about the geometric irregularity of the wear
scars can be made. Fig. 2 shows several possible wear conditions. In Fig. 2(a), the flat material is much more wear-resistant than
the ball material. In Fig. 2(b), the ball material is much more wear-resistant than the flat material. In Fig. 2(c), measurable wear
occurs on both ball and flat materials.
9.2 Wear of the Ball Specimen—Owing to the nature of this type of test, the wear scar on the ball specimen may not always be
circular or flat. Refer to the following which applies.
9.2.1 If the end of the ball appears flat, but not circular, the average of the maximum and minimum dimensions of the scar shall
be computed and this value used as the effective ball scar diameter (D). PinBall scar measurements may be made by removing the
ball specimen holder and placing the wear scar portion under a reflecting microscope. A calibrated ocular or ocular, a
photomicrograph of known magnification magnification, or a calibrated image measurement software may be used to measure scar
dimensions. Due to the typically high reflectivity of the ball surface, the use of an optical, noncontact profilometer may prove
difficult.
9.2.1.1 The wear volume (V ) for a flat ball wear scar of effective diameter D (the case in Fig. 2(a)), is found from the same
p
relationship given in Test Method G99, Appendix X1.1.1:
...