The research presented in this dissertation has produced an accurate unified tribological model to determine the fluid film and interacting forces between rotor and stator based on a realistic rough surface model. It also provides an overall solution strategy for calculation of forces for rotor-bearing interactions applied in the analysis of nonlinear rotordynamics problems.; Surface roughness is generated computationally and, by using an average flow model, allows effects of surface roughness with different geometries on journal bearing performance to be analyzed. A mathematical model is developed for mixed lubrication and asperity contact in order to evaluate the asperity contacts loading, friction force, real contact area and fraction of journal bearing load capacity by asperity contact.; A mathematical model for boundary lubrication in journal bearings has also been developed to determine the normal and traction contact forces. Stribeck type friction diagrams for different regimes of lubrication are computed and are in a good agreement with published experimental results. The rotordynamics rub phenomena studied is based on a boundary lubrication model and shows routes to chaos. Surface parameter effects, such as roughness and hardness on rotor casing interacting forces are analyzed.; By implementing the developed models for different regimes of lubrication in journal bearings, the transient dynamic analysis of a rotor in fluid film bearings has been studied based on realistically rough surfaces. Dynamical responses of the rotor in the presence of roughness indicates that a decrease of viscosity intensifies the influence of roughness in rotor trajectory and interacting forces. In the mixed lubrication region, short bearings are more influenced by surface roughness variation, compare to the long bearings. However, in the boundary lubrication region, all sizes of bearings are influenced by surface roughness variations.
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