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.
The models of normal and tangential oil film damping are established by modeling the viscous-elastic fluid as massless damping elements. The central pressure and film thickness distributions, friction coefficient, and maximum temperature rise with or without considering thermal effect indicate the proposed damping models and the solutions to the damping are valid. Thereafter, the thermal effect on oil film damping is discussed and the effects of contact force, rotation speed, and tooth number of spur gears in line contact non-Newtonian transient thermal elastohydrodynamic lubrication (EHL) on the oil film damping are investigated. The results imply that the larger damping in the normal direction is beneficial to meshing impact resistance and vibration reduction, whereas the smaller damping in the tangential direction is very helpful for fluidity enhancement and friction heat inhibition.
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