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Anatomy of an L-37 Hypoid Gear Durability Test Ridging Failure
Technical Paper
2012-01-1669
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
The ASTM D6121 (L-37) is a key hypoid gear lubricant durability test for ASTM D7450-08 (API Category GL-5) and the higher performance level SAE J2360. It is defined as the ‘Standard Test Method for Evaluation of Load-Carrying Capacity of Lubricants Under Conditions of Low Speed and High Torque Used for Final Hypoid Drive Axles’. Pass/fail is determined upon completion of the test by rating the pinion and ring gears for several types of surface distress, including wear, rippling, ridging, pitting, spalling and scoring. Passing the L-37 in addition to the other tests required for API Category GL-5 credentials, as well as the more strenuous SAE J2360 certification, requires in-depth formulating knowledge to appropriately balance the additive chemistry.
This paper describes the results of ASTM D6121 experiments run for the purposes of better understanding gear oil durability. Two gear lubricants, differing only in the antiwear chemistry, were used: gear lubricant A was designed to pass the test, while gear lubricant B was intentionally formulated to fail for gear ridging. In this series of experiments: the cooling demand required to maintain a constant oil temperature was monitored continuously; the oil was sampled every two hours for evaluation of changes in oil chemistry and particulate levels; and surface analysis was performed on end-of-test gears not only from tests run to completion, but also from tests stopped early.
It will be shown that gear ridging is an abrupt process, characterized by a sharp increase in cooling demand, iron content and particulate levels. Protective phosphate films are formed on the gear surfaces in the earliest stages of both passing and failing tests, but in ridging failures the phosphate is replaced by sulfide films not capable of providing adequate gear tooth protection, which then allows ridging.
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Authors
Citation
McFadden, C., Barton, W., Akucewich, E., Blanazs, L. et al., "Anatomy of an L-37 Hypoid Gear Durability Test Ridging Failure," SAE Technical Paper 2012-01-1669, 2012, https://doi.org/10.4271/2012-01-1669.Also In
References
- “Standard Test Method for Evaluation of Load-Carrying Capacity of Lubricants Under Conditions of Low Speed and High Torque Used for Final Hypoid Drive Axles,” ASTM Standard D6121 Oct. 2010
- “Standard Specification for Performance of Rear Axle Gear Lubricants Intended for API Category GL-5 Service,” ASTM Standard D7450 May 2008
- SAE International Surface Vehicle Standard “Lubricating Oil, Gear Multipurpose (Metric) Military Use,” SAE Standard J2360 Nov. 1998
- Shipley, E.E. “Gear Failures: How to Recognize Them, What Causes Them, How to Avoid Them,” Machine Design Dec 7 1967
- “Appearance of Gear Teeth - Terminology of Wear and Failure,” ANSI/AGMA Standard 1010-E95 Dec. 1995
- Jones, M.H. Scott, D. “Industrial Tribology: The Practical Aspects of Friction, Lubrication and Wear,” Elsevier Amsterdam 10: 044455677X 24 25 1991