A dynamic rheological model for thin-film lubrication

作     者：张向军 黄颖 郭岩宝 田煜 孟永钢 

作者机构：State Key Laboratory of Tribology Tsinghua University 

出 版 物：《Chinese Physics B》 (中国物理B（英文版）)

年 卷 期：2013年第22卷第1期

页      面：426-433页

核心收录：

学科分类：080103[工学-流体力学] 08[工学] 0801[工学-力学（可授工学、理学学位）] 

基　　金：Project sponsored by the National Basic Research Program of China (Grant No. 2012CB934101) the National Natural Science Foundation of China (Grant Nos. 50975154 and 51175282) 

主　　题：rheology viscoelasticity Deborah number thin-film lubrication 

摘      要：In this study, the effects of the non-Newtonian rheological properties of the lubricant in a thin-film lubrication regime between smooth surfaces were investigated. The thin-film lubrication regime typically appears in Stribeck curves with a clearly observable minimum coefficient of friction （COF） and a low-COF region, which is desired for its lower energy dissipation. A dynamic rheology of the lubricant from the hydrodynamic lubrication regime to the thin-film lubrication regime was proposed based on the convected Maxwell constitutive equation. This rheology model includes the increased relaxation time and the yield stress of the confined lubricant thin film, as well as their dependences on the lubricant film thickness. The Deborah number （De number） was adopted to describe the liquid-solid transition of the confined lubricant thin film under shearing. Then a series of Stribeck curves were calculated based on Tichy＇s extended lubrication equations with a perturbation of the De number. The results show that the minimum COF points in the Stribeck curve correspond to a critical De number of 1.0, indicating a liquid-to-solid transition of the confined lubricant film. Furthermore, the two proposed parameters in the dynamic rheological model, namely negative slipping length b （indicating the lubricant interracial effect） and the characteristic relaxation time λ0, were found to determine the minimum COF and the width of the low-COF region, both of which were required to optimize the shape of the Stribeck curve. The developed dynamic theological model interprets the correlation between the rheological and interfacial properties of lubricant and its lubrication behavior in the thin-film regime.