Traditional tribology is based on the surface with random micro structures due to limitations of manufacturing technology. The modern manufacturing technology now promises to fabricate surfaces with regular micro structures (or asperities). The word asperity refers to a single physical entity on the surface of a material, contributing to a concept called roughness in traditional tribology. Regular asperity surfaces imply that all asperities on the surface of a material have the same shape and size, and a deterministic distribution over the surface. The emergence of regular asperity surfaces will have a transformative impact to the discipline of tribology.<p>
The overall objective of this thesis is to study how the regular asperity would affect the tribological behavior. Specifically, this thesis develops a computational model to demonstrate and characterize the effect of the surface with regular anisotropic asperities (RAA) on the directional friction behavior when the surface is in a fully lubricated state. By directional friction, it is meant that friction force changes its magnitude with the change of the relative motion direction. By anisotropic asperity, it is meant that the geometry of the asperity is not symmetrical along the motion direction.<p>
This thesis presents a detailed development of the computational model by employing computational fluid dynamics (CFD) techniques. In particular, the model takes the Navier-Stokes (NS) equation as a governing equation and the Half-Sommerfeld Condition (HSC) to represent fluid behavior in the cavitation region; as such the model is named NS-HSC for short. Verification of the NS-HSC model is conducted with the information available in literature. A theory is proposed to explain the relationship between directional friction behavior and specific RAA structures. The thesis concludes: (1) the NS-HSC model is more accurate than the existing model in the literature and can be used to predict directional friction behavior and to design RAA surfaces, and (2) the proposed theory is excellent consistent with the NS-HSC model and thus useful to analysis and design of RAA surfaces for directional friction.<p>
The major contributions of this thesis are: (1) the first model in the field of tribology to predict the directional friction behavior for RAA surfaces under a fully lubricated status, (2) the first investigation, in the field of CFD, into combining the NS and HSC for modeling a laminar flow with cavitation, and (3) the first theory in the field of tribology for directional friction on fully lubricated RAA surfaces.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-09032010-165442 |
| Date | 16 September 2010 |
| Creators | Zhang, Zhiming |
| Contributors | Boulfiza, Mohamed, Burton, Richard T., Chen, Daniel, Zhang, Wenjun, Bergstrom, Donald J. |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-09032010-165442/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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