| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === Friction and wear, which are ubiquitous in the field of mechanical engineering, affect the life and performance of machines. An improper design would result in significance waste of material. Friction and wear exist at all contact surfaces and are directly influenced by the surface topology of the contact surfaces. As a consequence, the study of contact behavior between rough surfaces is an important topic.
Compared to traditional statistical surface model, which treats the surface as the collection of randomly distributed asperities, a fractal surface model has the merit of being scale independent. However, the analysis of contact behavior of fractal surfaces cannot be performed without using the results of traditional statistical surface model. Specifically, three basic assumptions are required as listed below: (1) The contact of two rough surfaces are equivalent to the contact of a rigid smooth surface and a rough surface. (2) The contact behavior of a fractal surface is approximately equal to a sinusoidal surface with a specified wave length. (3) The contact of a sinusoidal surface and a rigid flat surface is equivalent to the contact of a spherical asperity with a rigid flat surface.
In this thesis, we examined the above three assumptions using a commercially available FEM package. We studied the contact behavior between (i) ball-ball and ball-flat rigid surface contact pairs; (ii) single-sinusoidal-surface-rigid flat surface and multiple-sinusoidal-surface-rigid flat surface contact pairs; (iii) single-sinusoidal-surface-rigid flat surface and ball-rigid flat surface contact pairs. Due to numerical difficulties, the study of case (ii) doesn’t generate conclusive results. On the basis of (i) and (iii), we proposed conditions under which assumptions (1) and (3) hold.
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