This test method is used to determine the equilibrium rate of wear and coefficient of friction of materials in rubbing contact under useful operating conditions, that is, combinations of pressure and velocity that fall below the PV (pressure × velocity) limit of the test material. The user of this test method should determine to his own satisfaction whether the results of this test procedure correlate with field 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.
Test conditions may be selected from Table 1.
The precision of wear measurement is relatively independent 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 useful wear rate precision requires the selection of a test duration sufficient to produce 0.1 mm (0.004 in.) of wear. Test durations will often be in the 50 to 4000-h range.
TABLE 1 Test ConditionsA
| 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 | |||
|---|---|---|---|---|---|
| PV1 1250 (26.8) | PV2 2500 (53.6) | PV3 5000 (107.1) | PV4 10 000 (214.3) | ||
| 36 | 10 (3.05) | 25.0 (11.3) | 50.0 (22.7) | 100 (45.4) | 200 (90.7) |
| 180 | 50 (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− 5 in./h (2.5 × 10−7 m/h) is considered excessive. Typical wear rates for some commonly used materials at different PV levels are:
| Acetal homopolymer at PV1: | 5 × 10−6 to 1 × 10 −5 in./h (1.3 × 10−7 to 2.5 × 10− 7 m/h) | |
| Acetal homopolymer at PV2: | 1 × 10−5 to 3 × 10 −5 in./h (2.5 × 10−7 to 7.5 × 10− 7 m/h) | |
| 22 % PTFE-filled acetal homopolymer at PV2: | 3 × 10− 6 to 6 × 10−6 in./h (7.5 × 10−8 to 1.5 × 10 −7 m/h) | |
| Polyamide (Type 6-6) at PV2: | 1 × 10−5 to 5 × 10 −5 in./h (2.5 × 10−7 to 1.3 × 10− 6 m/h) | |
| 15 % graphite filled polyimide restin at PV3: | 1 × 10− 5 to 2 × 10−5 in./h (2.5 × 10−7 to 5 × 10 −7 m/h) |
1.1 This test method covers the determination of wear rate and coefficient of friction for self-lubricated materials in rubbing contact by a testing machine that utilizes a thrust washer specimen configuration.
Note 1—This machine may also be used to measure coefficient of friction.
1.2 The values in SI units are to be regarded as the standard. In cases where materials, products, or equipment are available only in inch-pound units, SI values 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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