Effects of Bingham-Visco-Elasticity of Greases on Creation and Disappear of Core in Fluid Film Lubrication

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The object of this project is to clarify an effect of Bingham-visco-elasticity of greases on creation and disappear of core in fluid film lubrication, because a grease in used in practice due to easy lubrication system as compared with that by other lubricants such as oil.A rheology equation supposed in this project, which consists of one slider and two nonlinear dashpots and two non-linear springs, is investigated experimentally for the various kinds of commercial grease by using rotational and vibrational rheometer.By introducing yield stress tensor to the above rheology equation and to fluid film lubrication theory, lubrication equations are derived for Cartesian and cylindrical coordinates by considering time dependence on creation and disappear fo core fluid film. These lubrication equations are different types whether core occurs or not, due to Bingham characteristics of greases.On the other hand, by using step squeeze thrust bearings tester with such greases, profiles of core are measured by camera under wedge and squeeze action. Characteristics of Bingham-visco-elasticity of lubricants on the core formations of greases in fluid film lubrication are clarified.