d4170--微动磨损.pdf

Designation: D 4170 – 97 Standard Test Method for Fretting Wear Protection by Lubricating Greases1 This standard is issued under the fi xed designation D 4170; 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 1.1 This test method evaluates the fretting wear protection provided by lubricating greases. 1.2 The values stated in SI units are to be regarded as the standard. Other units 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 appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. For specifi c hazard statements, See Note 2, Note 3, and Note 5. 2. Referenced Documents 2.1ASTM Standards: Test Methods for Rating Motor, Diesel, and Aviation Fuels; Motor Fuels (Section I), Reference Materials and Blend- ing Accessories (Annex 2), Reference Fuels (A2.7.3.3), and Table 32 (Specifi cation for n-Heptane Motor Fuel)2 2.2Military Standard:3 MIL-S-22473D Sealing, Locking and Retaining Com- pounds, Single-Component 3. Terminology 3.1 Defi nitions: 3.1.1 fretting wear, n—a form of attritive wear caused by vibratory or oscillatory motion of limited amplitude character- ized by the removal of fi nely-divided particles from the rubbing surfaces.4 3.1.1.1 Discussion—Air can cause immediate local oxida- tion of the wear particles produced by fretting wear. In addition, environmental moisture or humidity can hydrate the oxidation product. In the case of ferrous metals, the oxidized wear debris is abrasive iron oxide (Fe2O3) having the appear- ance of rust, which gives rise to the nearly synonymous terms, fretting corrosion and friction oxidation. A related, but some- what different phenomenon often accompanies fretting wear. False brinelling is localized fretting wear that occurs when the rolling elements of a bearing vibrate or oscillate with small amplitude while pressed against the bearing race. The mecha- nism proceeds in stages: 1) asperities weld, are torn apart, and form wear debris that is subsequently oxidized; 2) due to the small-amplitude motion, the oxidized detritus cannot readily escape, and being abrasive, the oxidized wear debris acceler- ates the wear. As a result, wear depressions are formed in the bearing race. These depressions appear similar to the Brinell depressions obtained with static overloading. Although false brinelling can occur in this test, it is not characterized as such, and instead, it is included in the determination of fretting wear. 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. NOTE1—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 (63 %) at the assembled length of the spring. 5. Signifi cance 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 specifi cation purposes, differenti- ates 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.5Test 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. 6. Apparatus 6.1 Falex Fretting Wear Tester, Model F-1581, 6,7 as pur- chased and illustrated in Figs. 1 and 2. 1This test method is under the jurisdiction of ASTM Committee D-2 on Petroleum Products and Lubricantsand is the direct responsibility of Subcommittee D02.Gon Lubricating Grease. Current edition approved June 10, 1997. Published December 1997. Originally published as D 4170 – 82. Last previous edition D 4170 – 93. 2Annual Book of ASTM Standards, Vol 05.04. 3Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. 4NLGI Lubricating Grease Guide, 3rd edition (to be published). 5Verdura, T. M., “Development of a Standard Test to Evaluate Fretting Protection Quality of Lubricating Grease,” NLGI Spok。