In this study, the wear depths under different loads, speeds, lubricant temperatures, and surface roughness amplitudes are experimentally determined using a twin-disk rolling contact setup. A point contact wear model combining a contact formulation and Archard's wear equation in an iterative manner is developed to simulate the wear process of the experiments. By matching the measured and predicted wear profiles, the wear coefficients under different operating and surface conditions are determined. It is found that the wear coefficient increases when either the load or the surface roughness amplitude increases and decreases as the lubricant pressure-viscosity coefficient increases. Within the operating ranges considered, it is observed that the lubricant pressure-viscosity coefficient is the most influential parameter on wear, the load has the least impact, and the surface roughness amplitude is in between. Lastly, a regression formula is given for the estimation of Archard's wear coefficient.

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In this study, steady-state mechanical power loss model of an automatic transmission gear train consisting of multiple stages of planetary gear sets is developed. Load dependent (mechanical) power losses at the internal (ring-planet) and external (sun-planet) gear meshes and planet bearing interfaces are included through elastohydrodynamic lubrication (EHL) based power loss formulations. At the end, efficiency of an 8-speed automatic transmission is studied under representative operating conditions to quantify the contribution of various loss mechanisms to the total loss under variable speed, load and temperature conditions. Impact of gear surface roughness amplitudes on the resultant power losses is also described. Keywords

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