Optimization of surface texture shapes in hydrodynamic contacts

[Truncated abstract] The development of an optimization system/method for surface textures in hydrodynamic contacts is of great importance to tribology. Such method, once developed, would replace inefficient techniques that have been used to date in determining the optimum surface texture shapes of mechanical components. Various attempts at finding optimal texture shapes have been made, but most of them have been limited to either numerical or experimental exhaustive searches which are both costly and time consuming. Few works exist that employ numerical optimization techniques; most of them are only applicable to specific cases they were designed for. Thus, there is an urgent need for the development of a new optimization approach that would be versatile and more efficient than previously used methods. This thesis is divided into six parts. The first part contains introduction, thesis objectives, overview and review of, literature; in the second part the numerical methodology is outlined, in the third part a new unified approach is designed to optimize 1D hydrodynamic bearings governed by the Reynolds equation. The approach is based on the theory of optimal parameter selection, control parametrization and nonlinear programming. The method can be used to optimize hydrodynamic bearing texture shapes to obtain maximum load capacity or minimum friction force/coefficient. It has been validated by comparison of obtained results to published data when possible and to the results of performed parametric exhaustive search. The method was tested on a number of cases, including smooth 1D journal and pad bearings, parallel 1D sliders with rectangular and elliptical dimples; bearings lubricated with non- Newtonian fluids and lubricant viscosity changing with temperature were also studied. Cavitation was taken into account by using the Reynolds boundary condition. The approach was proved to yield correct results and thus formed a foundation of our following works.