The effect of friction on micropitting

Micropitting is a type of surface fatigue damage that occurs in rolling-sliding contacts operating under thin oil film conditions. It caused by stress fluctuations, brought about asperity interactions, which lead to initiation and propagation numerous cracks subsequent loss material. Despite its increasing importance gear bearing reliability, the mechanisms micropitting are poorly understood. This particularly case concerning effects friction on difficult study controlled because it isolate from other influential factors, particular build-up any anti-wear tribofilm effect running-in counterface roughness known strongly affect through influence severity stresses. paper presents new data impact obtained using test methodology. tests were conducted ball-on-disc MTM rig with additional functionality continuously monitor growth during test. Friction was varied custom-made oils containing different concentrations MoDTC. Crucially, isolated introducing MoDTC blend only after period completed ZDDP solution alone. approach eliminates early stages hence ensures same takes place each gives similar pressure history, regardless amount present. Results show has very significant micropitting; for example, extent reduced factor 10 when coefficient 0.1 0.04. Lower results fewer grow at shallower angle than those higher friction. Numerical analysis contact stresses present tested conditions indicates primary mechanism affects near fields: reducing reduces local tensile shear surface, asperity-influenced region, may turn be expected mitigate crack propagation. The presented help designing formulations can extend component lifetimes respect both wear controlling