Doctor of Philosophy (PhD)


Mechanical Engineering

Document Type



Gears are widely used in industry and hence their performance is of vital importance. Under the typical operating conditions of gears, the lubricant layer formed between the teeth of the pinion and the gear cannot completely separate the surfaces and contact of asperities of the pinion and gear occurs. This case is usually referred to as mixed lubrication problem. In this research the load-sharing concept has been employed to predict the performance of the pinion-gear system. The load-sharing concept is an efficient method to solve the mixed lubrication problem and is capable to predict the thickness of the lubricant film, contribution of the fluid film and asperities in carrying the load, friction coefficient, lubricant temperature, and wear with fairly good accuracy. During the initial stage of contact, a considerable number of plastic contact occurs between asperities resulting in permanent change of surface roughness profile. This period which is called running-in has a significant effect on the steady-state performance of the pinion-gear system. The developed model has the capability to predict the variation of surface roughness and contribution of fluid film as well as asperities in carrying the load during running-in. The steady-state wear of gears is predicted using the thermal desorption model. A test rig is designed and built which is capable to mimic the operating condition of any point on the involute profile of gear. Two motors are used to rotate the rollers to generate the same rolling and sliding speed as the corresponding point of the involute profile of pinion-gear system. A hydraulic system is used to exert the desired load on the rollers and keep them in contact under the applied load. The sensors that are mounted on this test rig monitor the speed of each shaft, applied load, surface temperature, and wear depth. The results of the experiments that are conducted on the fresh rollers as well as broken-in roller are shown to be in good agreement with the predicted running-in behavior and steady-state behavior, respectively.



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Committee Chair

Khonsari, Michael