During their lifetime, gears may undergo starved lubrication operating conditions. Starvation condition has an impact on friction between gears that leads to modify gearbox efficiency. In this paper, lubricant starvation tests on an FZG test rig adapted to this condition are presented.Gears were equipped with embedded thermocouple sensor to measure their operating bulk temperature. An experimental method to isolate test box power loss of FZG machine is proposed. A thermal model of this test rig draws up the power loss distribution into the test box for a nominal condition of lubrication. At last, a numerical method based on experimental results is proposed to estimate gear power loss variation during lubricant starvation.

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This paper investigates the strong coupling between friction power losses and film thickness that prevent from clearly identifying the mechanism of scuffing through classical test procedures. As the film thickness appears of great influence on the phenomena, a new test method is presented, allowing scuffing initiation study with the film thickness as a key parameter. This new test method allows film thickness variation with minimal friction losses and bulk temperature variations. This procedure has been developed with nitrided steels and a synthetic base oil on a twin disks test rig. Even though asperity contact is considered necessary in literature for scuffing, the test result shows that it can be reached in full film lubrication, potentially through the collapse of the oil film. Different test methods allowing triggering scuffing through different parameters are identified, which shows that a variety of parameters is able to influence scuffing.