Doctor of Philosophy (PhD)


Mechanical Engineering

Document Type



The dissertation focuses on the frictional characteristics of journal bearings as represented by the Stribeck curve. The behavior of lift-off speed and the factors that affect it are explored. An equation is proposed for predicting the lift-off speed. The comparison between the experimental results of oil- and grease-lubricated journal bearings with a mixed elastohydrodynamic lubrication model for line contacts is indicative of good agreement in the mixed lubrication regime. Efforts are made to modify the surface profile of bushing by putting dimples on its surface. Experimental results show that with proper dimensions of dimples, the friction performance of journal bearings can be improved, particularly for light oils. The friction hysteresis of oil and grease-lubricated journal bearings undergoing oscillatory motion are investigated under different load, with or without oil, oil type, oil inlet temperature, oscillating frequency, and bushing material. A dynamic friction model for infinitely long journal bearing is also developed that demonstrates the existence of hysteresis loop. Finally, a thermal analysis of oscillatory journal bearings is carried out by finite element method using ANSYS. Simulations are found to be in good agreement with experimental measurement of temperature at four locations along the circumference.



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Committee Chair

Michael M. Khonsari