PERFORMANCE CLASSIFICATION OF AUTOMOTIVE GEAR OILS USING THE GEAR SCUFFING SHOCK TEST
Journal Title: Tribologia - Year 2009, Vol 224, Issue 2
Abstract
Nowadays, one of the important current problems of tribology is differentiating between oils of high EP (extreme-pressure) properties. Examples of such oils are automotive gear oils of high performance levels API GL-3 to GL-5. The author presents a new test method intended for differentiating between such oils from the point of view of their API performance level. The method is called “scuffing shock test” and denoted as S-A10/16,6R/120. It concerns gear testing and has been developed in the Gear Research Centre (FZG) at the Technical University of Munich. The shock test is carried out under much severer conditions (reduced face width, double rotational speed, higher initial temperature of the tested oil, reverse sense of rotations) than the most often employed FZG gear scuffing test denoted as A/8,3/90. Unlike the other FZG gear scuffing tests, in which the load is increased in stages from the lowest value, in S-A10/16,6R/120 test the expected failure load is applied to an unused gear flank, hence the name “shock test”. This prevents the test gears from running-in and in turn increases their susceptibility to scuffing. The shock test has been verified using a series of automotive gear oils of the following API performance levels: GL-3, GL-4, GL-4/5, GL-5 and GL-5(LS). For reference, API GL-1 gear oils, showing the poorest performance, were also tested. A test rig denoted as T-12U, designed and manufactured by ITeE-PIB in Radom, was used. It has been shown that the shock test makes it possible to differentiate between automotive gear oils of API GL-3 performance level and oils of higher levels. Although it is impossible to differentiate between automotive gear oils of the highest specifications (GL-4, GL- 4/GL-5, GL-5), one can distinguish between oils belonging to the same performance level. What is particularly important is that none of the tested oil exhibited the failure load stage (being a measure of EP properties of oils tested) higher than 11. This implies that the test conditions in the shock test are severe enough to differentiate between modern automotive gear oils. The presented gear scuffing shock test can be implemented in the R&D laboratories of the petroleum industry, but also in the laboratories of the R&D centres devoted to surface engineering and engineering of advanced materials intended for modern toothed gears.<br/><br/>
Authors and Affiliations
Waldemar Tuszyński
Keywords
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