| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
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
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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
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