Ha-Rok Bae (Committee Member), Ahmet Kahraman (Committee Member), Sheng Li (Advisor), Nikolai Priezjev (Committee Member), Joseph Slater (Committee Member)
Doctor of Philosophy (PhD)
Gears are vital power transmitting mechanical components, in both automotive and aerospace applications, and commonly operate within relatively high rotational speed ranges. Therefore, the dynamic behavior of gears is inevitable and can be quite significant under certain circumstances. The gear dynamics introduces not only noises and vibrations, but also large tooth force amplitudes, and consequently large amplitudes of bending stresses and contact stresses, and high surface temperatures, promoting the failures of tooth bending fatigue, contact fatigue, and scuffing. This study focuses on the mechanism by which the gear dynamic responses affect the flash temperature rise and contact fatigue life using a gear tribo-dynamic formulation. The significance of this work is that it connects the gear dynamics and gear tribology disciplines and shows the importance of dynamic response on the two critical failure modes; scuffing and pitting. A six degree-of-freedom transverse-torsional discrete gear dynamics equation set is coupled with a thermal mixed elastohydrodynamic lubrication formulation to include the interactions between the gear dynamics and the gear tribological behavior. The flash temperature rises are quantified within a wide speed range under the different operating and surface conditions. The results indicate evident deviations of flash temperature rise between quasi-static condition and tribo-dynamic condition especially in the vicinities of the resonances. The interactive model of gear dynamics and gear tribological behavior is bridged through an iterative numerical scheme to determine the surface normal pressure and tangential shear under the tribo-dynamic condition. The resultant multi-axial stress fields (from these surface tractions) on and below the surface are then used to assess the fatigue damage. A comparison between the tribo-dynamic and quasi-static life predictions is performed to demonstrate the important role of the gear tribo-dynamics in the fatigue damage. The impacts of the input torque, surface roughness and lubricant temperature on the gear contact fatigue under the tribo-dynamic condition are also investigated. The results show that the fatigue life under tribo-dynamic conditions show large deviations at the vicinities of the resonances when compared to the quasi-static conditions.
Department or Program
Ph.D. in Engineering
Year Degree Awarded
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