Abstract:Based on a theoretical model and an experimental methodology for defining the friction torque for lubricated conditions in a modified thrust ball bearing having only three balls, the authors experimentally investigated the influence of the lubricant parameter Λ on friction torque for mixed IVR (isoviscous rigid) and EHL (elastohydrodynamic) lubrication conditions. The experiments were conducted using ball diameters of 3 mm, 3.97 mm and 6.35 mm loaded at 0.125 N, 0.400 N and 0.633 N. Two oils of viscosity 0.08 Pa·s and 0.05 Pa·s were used and rotational speed was varied in the range 60-210 rpm to obtain a lubricant parameter Λ varying between 0.3 and 3.2. The experiments confirmed that the measured friction torque can be explained using hydrodynamic rolling force relationships respecting the transition from an IVR to an EHL lubrication regime.
The behavior of the contact surfaces between the gear teeth has a significant influence on the gear service properties. An analytical research concerning this behavior by considering a non Hertzian model was developed. A mathematical model of the surfaces of the teeth flanks for modified involute spur gears with crowning and relieving was presented. The pressure distribution, displacement and contact surfaces were analyzed, on considering the load, material characteristics and geometry of the contact surfaces and using a numerical method.
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