AGMA 06FTM07-2006 pdf free.Improvement of Standardized Test Methods for Evaluating the Lubricant Influence on Micropitting and Pitting Resistance of Case Carburized Gears.
Micropitting on gears is a surface fatigue damage that is strongly influenced by the conditions of the tribological system consisting of the tooth flank surface and the lubricant. Micropitting is most frequently observed on gear flanks with a high surface hardness and normally starts in flank areas with high negative specific sliding. The damage pattern of micropitting is characterized by a large number of microscopic cracks. Small pits originating from these cracks can result in a removal of surface material and create local flank wear (Fig. 1).
Consequently progressing micropitting can cause increasing changes of the involute profile in form of profile deviations. In this case the dynamical additional forces and the gear noise can increase and the occurrence of pitting may be influenced.
The FVA-FZG micropitting test acc. to [3] is well established as a standard test method for evaluating the micropitting load capacity of gear lubricants. The test provides a quantitative evaluation of the influence of lubricant (especially additives) on the occurrence of micropitting, differentiates oils according to their micropitting load capacity and enables the choice of a lubricant with a sufficient micropitting resistance. The results of the test can be introduced into a micropitting capacity rating method for gears
[6, 10, 11].
The FZG micropitting test consists of a load stage test with incremental increasing of the contact stress followed by an endurance test. In the load stage test the ability of the tribological system to resist micropitting is determined in form of a failure load stage. The endurance test provides additional information on the damage progression after higher numbers of load cycles. This test method provides precise results, but requires relatively high costs and is quite time-consuming. An efficient and consistent short test method to evaluate the lubricant influence on micropitting has been missing so far. Therefore the available FVA-FZG micropitting test was supplemented by a standardized short test method, that is able to classify candidate lubricants analogous to the existing test method.
FZG Micropitting Test GT acc. to FVA 54/7
Fig. 2 shows schematically the test procedure of FZG micropitting test acc. to FVA-information sheet 54/7 [3] (for test conditions see also Fig. 4).AGMA 06FTM07 pdf free download.