ASTM D4170 test method for fretting wear protection by lubricating greases
4. Summary of Test Method
4.1 The tester is operated with two ball thrust bearings, lubricated with the test grease, oscillated through an arc of 0.21 rad (12°), at a frequency of 30.0 Hz (1800 cpm), under a load of 2450 N (550 lbf), for 22 h at room temperature (Note 1). Fretting wear is determined by measuring the mass loss of the bearing races.
NOTE 1 - Arc, frequency, and load are factory-set operating conditions and should not be altered. The load spring constant may change over an extended time period. Spring calibration should be checked periodically and, if necessary, a suitable shim should be fabricated to obtain the required load (+/- 3 %) at the assembled length of the spring.
5. Significance and Use
5.1 This test method is used to evaluate the property of lubricating greases to protect oscillating bearings from fretting wear. This method, used for specification purposes, differentiates among greases allowing low, medium, and high amounts of fretting wear under the prescribed test conditions. The test has been used to predict the fretting performance of greases in wheel bearings of passenger cars shipped long distances. Test results do not necessarily correlate with results from other types of service. It is the responsibility of the user to determine whether test results correlate with other types of service.
