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Innovative stiffness and damping models for oil films are developed to account for the impacts in both normal and tangential directions. Given that these models are applied to a gear drive in line contact elastohydrodynamic lubrication (EHL), the combined stiffness is derived from the stiffness of both the oil film and gear tooth while the combined damping is established from the damping of these parts. The effects of three fundamental parameters (contact force, rotation speed, and tooth numbers) of the gear drive in line contact EHL on the combined stiffness and damping are then investigated. The results reveal that the small normal and tangential stiffness of the lubricant can alleviate meshing impact and shear vibration, while the impact and friction heat can be reduced by using an oil film with either a large normal damping or small tangential damping. Given that its amplitude and fluctuation are closely related to shear rate, effective viscosity, entrainment velocity, and curvature radii, the improved combined stiffness and damping can be obtained by rationally matching the geometric and operating parameters. [ABSTRACT FROM AUTHOR]

A new normal stiffness model of the oil film is established by the viscous-elastic fluid between a spur gear drive being equivalent to a massless spring element, and the tangential stiffness model is proposed according to the hypothesis of equal shear stress on laminar element surfaces. Effects of operating parameters (contact force and rotation speed) and geometry parameters (module, tooth number, pressure angle and modification) on the oil film stiffness from the root to the tip are investigated. The results show that the amplitude and fluctuation of the stiffness are closely related to the shear rate, effective viscosity and curvature radii. It is indicated that the rational parameter match is valid in mesh impact reduction and stationarity enhancement. [ABSTRACT FROM AUTHOR]