MECHANISM OF GREASE FILM FORMATION IN ELASTOHYDRODYNAMIC POINT CONTACTS

润滑脂已被广泛用作许多机械零件的润滑剂。然而，在应用之前，我们还不能准确地预测润滑脂的润滑性能。这是因为对润滑脂在弹性流体动力润滑(EHL)状态下的行为还没有必要的了解。本研究的目的是利用光学干涉技术，通过对润滑膜的直接观察，阐明点弹流润滑接触中润滑膜的形成机理。试验润滑脂为不含添加剂的二脲基润滑脂，由芳香族、脂环族和脂肪族三种不同的稠化剂组成。结果发现，增稠器的结构对成膜和牵引特性有很大的影响。此外，还提出了新的润滑脂结构模型：芳香族润滑脂的增稠剂分散在基础油中。脂肪族润滑脂是由较稠密的纤维缠绕在一起形成的。I…更宽的空间。脂环脂具有芳香族和脂肪族润滑脂之间的中间纤维结构。得到的其他重要结果概括如下：1.相同浓度的润滑脂的膜总厚度依次变薄，依次为脂环类、芳香族、脂肪族润滑脂。以脂肪族二脲为增稠剂的复合润滑脂的膜厚与仅含脂肪族二脲的润滑脂的膜厚基本相同。相同稠化结构的润滑脂的总膜厚度随着基础油粘度的增加而增加。最大油膜厚度和最小油膜厚度分别由基础油的增稠剂和粘度决定。增稠剂与表面的粘附性导致薄膜整体厚度较厚。增稠剂在表面上的沉积和脱离受表面间的相对滑动控制。附着在表面上的较厚的团块表现为类似固体的材料，例如表面凸起。饥饿状态的发生取决于稠化剂的结构和基础油的粘度。牵引系数的大小顺序为芳香型、无气型、无环型。作为稠化剂之一的复合润滑脂的牵引系数与仅含脂肪族尿基的润滑脂的牵引系数基本相同。横向沟槽和长凸起对润滑脂弹流体膜的影响与对矿物油润滑的弹流体膜的影响基本相同。较少

Greases have been widely used as lubricants for numerous machine elements. Nevertheless, we cannot yet predict lubricating performance of greases accurately in advance of the application. This is because the behavior of greases in elastohydrodynamic lubrication (EHL) regime has not been necessarily understood. The purpose of this study is to elucidate the mechanism of grease film formation in point EHL contacts hased on direct observations of grease films using the optical interferometry technique. As test greases, diurea greases, without additives, constituting of three different kinds of thickeners, i.e., aromatic, alicyclic and aliphatic diurca, were used. As a result, it has found that the thickener structure plays tremendous roles on the film formation and traction characteristics. Furthermore, new models of grease structures have been proposed : The thickener of aromatic grease is dispersed in the base oil. The aliphatic grease is composed of thickener fibers entangled together i … More n wide space. The alicyclic grease has intermediate fiber structures between the aromatic and aliphatic greases. The other important results obtained are summarized as follows :1. The overall film thicknesses of greases having the same thickener content become thinner in the order, alicyclic, aromatic, aliphatic greases.2. The overall film thickness of combined grease containing aliphatic diurea as one of the thickeners is almost the same as that of grease containing only aliphatic diurea.3. The overall film thicknesses of greases constituting of the same thickener structure increase as the base oil viscosity increases.4. The maximum and minimum film thicknesses are mainly determined by the thickener and viscosity of the base oil, respectively.5. The adhesion of thickener to the surfaces brings about thick overall film thickness.6. The deposition and detachment of thickener to and from the surfaces are controlled by the relative sliding between surfaces.7. The thickener lump adhered to the surfaces behaves as a solid-like material such as a surface bump.8. The occurrence of the starved condition depends on the thickener structure and viscosity of the base oil.9. The traction coefficient becomes .smaller in the order, aromatic, ahiphatic, ahicyclic greases.10. The traction coefficient of combined grease containing alipliatic diurca as one of the thickeners is almost the same as that of grease containing only aliphatic diurea.11. The effects of a transversely oriented groove and a long bump on grease EHL films are basically the same as those on EHL films lubricated by mineral oils. Less