Numerical investigation of non-Newtonian and surface roughness effects on the performance of dynamically loaded journal bearings

This thesis is concerned with the development of computational analysis for the performance of dynamically loaded journal bearings with consideration of lubricant degradation and surface roughness patterns. The governing equation is the averaged Reynolds equation. The numerical approach is based on the finite element mass-conserving algorithm, proposed by Kumar and Booker.; Lubricant degradation concerns non-Newtonian effects on the performance of dynamically loaded journal bearings. A constitutive equation for multi-grade oils that can accommodate different rheological equations while providing reasonable agreement with experimental data has been implemented. Predicted results agree well with values obtained from finite difference cavitation algorithms.; The approach used to analyze various surface roughness patterns is based on the averaged Reynolds equation, proposed by Christensen, and Pair and Cheng, in which flow factors are used to modify the flow due to roughness effects. Three surface roughness patterns were investigated. The surface roughness patterns combined with the non-Newtonian lubricant behavior are incorporated to analyze the performance of journal bearings subjected to dynamic loading.; Three types of finite element grids were utilized in developed for the analysis of dynamically loaded journal bearings. Moreover, the impact of cavitation erosion, element sizes, time steps and numerical methods on the performance of dynamically loaded journal bearings are also investigated.; Computer programs based on the averaged Reynolds equation are developed to implement the various conditions considered. Journal bearings with elliptical contours are numerically considered when operating under very realistic conditions.