| Surface contact fatigue, as a lubrication-related gear tooth failure mode, is the main failure mode for heavy duty drive gears. So it is of great importance to study the influence of oil characteristics on the contact fatigue of heavy duty gears.The research focused on the heavy duty drives gears of a specific vehicle. In this paper, empirical method, theoretical method and numerical method were brought on to accurately calculate the Hertzian contact pressure of meshing tooth, respectively. The gear surface morphology of a sampling area at the position engaged in meshing was obtained with the help of White Light Interferometer, and a following simulation of rough-surface-contact was done based on the morphology. Two sets of gear tests was carried on the gear fatigue test rig, the only variation is the gear oil, and test results were collected and analyzed.This paper reached the following conclusions:(1)According to the theoretical results, for involute cylindrical gears whose modulus equals 6mm, the maximum Hertzian Pressure is 1.1 times current design value, and the engaged position is a little below the pitch circle line.(2)According to the simulation results based on the measured roughness, the real Hertzian Pressure is 4~6 times the result based on ideal surface, and the real contact area is 30%~50% of the nominal contact area.(3)According to the gear fatigue test, the base oil did not have a predominant effect on gear tooth surface fatigue. After the run-in period, the EP additive won’t accelerate the progress of micro-pitting, and the friction modifiers in additive package seems to inhibit the expansion of micro-pitting progress. Clear oil result in longer fatigue life.The main innovation of this paper lies in:(1)Prove the prediction of position where micro-pitting originates;(2)Measured roughness was used in the simulation;(3)Design a set of gear tests using DU test-rig to compare two different gear oil. |
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