Predictions of friction and flash temperature in marine gears based on a 3D line contact mixed lubrication model considering measured surface roughness

Wear and scuffing failures often occur in marine transmission gears due to high friction and flash temperature at the interface between the meshing-teeth. In this paper, a numerical solution procedure was developed for the predictions of transient friction and flash temperature in the marine timing gears during one meshing circle based on the 3D line contact mixed lubrication simulation, which had been verified by comparing the flash temperature with those from Blok’s theory. The effect of machined surface roughness on the mixed lubrication characteristics is studied. The obtained results for several typical gear pairs indicate that gear pair 4–6 exhibits the largest friction and the highest interfacial temperature increase due to severe rough surface asperity contacts, while the polished gear surfaces yield the smallest friction and the lowest interfacial temperature. In addition, the influences of the operating conditions and the gear design parameters on the friction-temperature behaviors are discussed. It is observed that the conditions of heavy load and low rotational velocity usually lead to significantly increased friction and temperature. In the meantime, by optimizing the gear design parameters, such as the modulus and the pressure angle, the performance of interfacial friction and temperature can be significantly improved.