Abstracts Category : Other

On the Thermal and Contact Fatigue Behavior of Gear Contactsunder Tribo-dynamic Condition

by Anusha Anisetti

Gears are vital power transmitting mechanicalcomponents, in both automotive and aerospace applications, andcommonly operate within relatively high rotational speed ranges.Therefore, the dynamic behavior of gears is inevitable and can bequite significant under certain circumstances. The gear dynamicsintroduces not only noises and vibrations, but also large toothforce amplitudes, and consequently large amplitudes of bendingstresses 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 geardynamic responses affect the flash temperature rise and contactfatigue life using a gear tribo-dynamic formulation. Thesignificance of this work is that it connects the gear dynamics andgear tribology disciplines and shows the importance of dynamicresponse on the two critical failure modes; scuffing and pitting. Asix degree-of-freedom transverse-torsional discrete gear dynamicsequation set is coupled with a thermal mixed elastohydrodynamiclubrication formulation to include the interactions between thegear dynamics and the gear tribological behavior. The flashtemperature rises are quantified within a wide speed range underthe different operating and surface conditions. The resultsindicate evident deviations of flash temperature rise betweenquasi-static condition and tribo-dynamic condition especially inthe vicinities of the resonances. The interactive model of geardynamics and gear tribological behavior is bridged through aniterative numerical scheme to determine the surface normal pressureand tangential shear under the tribo-dynamic condition. Theresultant multi-axial stress fields (from these surface tractions)on and below the surface are then used to assess the fatiguedamage. A comparison between the tribo-dynamic and quasi-staticlife predictions is performed to demonstrate the important role ofthe gear tribo-dynamics in the fatigue damage. The impacts of theinput torque, surface roughness and lubricant temperature on thegear contact fatigue under the tribo-dynamic condition are alsoinvestigated. The results show that the fatigue life undertribo-dynamic conditions show large deviations at the vicinities ofthe resonances when compared to the quasi-staticconditions.Advisors/Committee Members: Li, Sheng (Advisor).