Grain Flow Lubrication: Model for Rough Surfaces and Its Applications

• Main Authors: Hung-Jung Tsai, 蔡宏榮
• Other Authors: Yeau-Ren Jeng
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/95954890217620250523

博士 === 國立中正大學 === 機械系 === 91 === The use of powders has become a topic of significant interest due to their application in powder lubricated bearings at very high temperatures and speeds and in ultra-precision polishing. With the decreasing film thickness of manufacture and the increasing demand for higher precision, the influence of roughness becomes important. The purpose of this thesis is base on grain flow theory and average flow model, establish the generalized average lubrication equation for grain flow with surface roughness effects, and used to analyze the performance of slider bearings and the mechanism of chemical mechanical polishing. The thesis consists two main parts: theory derivation and application. In theory derivation, the generalized average lubrication equation including the interaction between grain flow characteristics and the effects of roughness is derived. This equation is based on Haff’s grain flow theory and the ensemble average flow model with coordinate transformation and the perturbation series approach with Green function technique. The analytical flow factors are expressed in terms of grain flow characteristics ( film particle ratios, grain size coefficient and the collision pattern including elastic and inelastic grain collision) and surface characteristics ( Peklenik number, orientation angle, the standard deviation of the roughness height of each surface and film thickness ratio). In its application, the generalized average lubrication equation for grain flow is applied to slider bearings and Chemical Mechanical Polishing. The performance of rough slider bearings is analyzed using a control volume method. The mean shear stress is derived in terms of shear stress factors. The effects of roughness on load, shear force, mean bearing inflow and side flow were analyzed for different surface characteristics and film particle ratios under various slenderness ratios. Besides, the generalized average lubrication equation is used to analyze slurry flow between wafer and pad and taking into account both grain flow and roughness effects. This improved model predicts slurry flow film thickness and attack angle under a variety of the CMP parameters including applied load, rotation speed, dome height, particle size and pad roughness. Furthermore, the influence of particle size and pad asperity on removal rate are investigated. The results compare well with experimental data in the literature.