Zhang Chaohui

(School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044)

Luo Jianbin  Wen Shizhu

(State of Key Laboratory of Tribology, Tsinghua University, Beijing 100084)

Abstract: The velocity field of thin film lubrication (TFL) lubricated with the ordered molecules is investigated. TFL is essentially a lubrication regime in which the ordered molecules play a dominant role. The orientation of ordered molecules is similar to that of nematic liquid crystal molecules and subsequently a vector, the director, can describe it. The velocity field and molecules’ ordering can be analyzed with the use of theories of nematic liquid crystals, and consequently the properties of lubrication with ordered molecules could be obtained. The differences, however, because the alignments are resulted from the surface forces of the solid walls, express in that the pertinent Leslie coefficients are not prescribed as the nematics are. The discrepancy of TFL from EHL comes from the elasticity of the ordered molecules. The viscosity-to-elasticity ratio can account for it well. The distributions of the director at various viscosity-to-elasticity ratios, as well as the effective viscosity, are presented. The corresponding velocity field is also presented. The research exhibits the feasibility of using the liquid crystals theory in TFL analyzing.

Key words: Thin film lubrication  Ordered molecules  Liquid crystal  Velocity field

CLC No: TH117

国家自然科学基金(90206022)和杰出青年基金(50025515)资助项目. Received 20031109, received in revised form 20040511