Chapter 6 - Lubrication Flashcards
Friction between moving surfaces are grouped in 3 main categories, what are they?
Sliding friction
Rolling friction
Fluid friction
What are two examples of sliding friction
Journal bearings or pistons sliding in a cylinder
In sliding friction the contact pressure is usually spread over a large area, this means the pressure per square inch is comparatively…
Light
When a spherical or cylindrical body rolls over a surface
Rolling friction
When lubricating oil is applied to two surfaces, what happens
A film of oil is formed, filling up depressions and covering the projections on both surfaces
Sliding that occurs between the layer of oil within the film is called
Fluid friction
What is lubricación
The reduction of fluid to a minimum by the replacement of dry friction with fluid friction
What is the theory of adhesion?
Adhesive forces cause unlike materials to stick together
Ex. Grease to metal, oil to metal
What is the theory of cohesion?
Cohesive forces cause molecules of like materials to stock together
Examples
Grease molecules and oil molecules
Oil forms in layers of…
Globules
The layers of globules roll over each other as long as there is enough…
Oil
Some molecules are attracted and held more strongly to metal than others. This property is called…
Oiliness or lubricity
What is viscosity?
The resistance of flow
The molecules in higher viscosity oils have a hard time…
Sliding past one another
What is the most important property of lubricating oil
Viscosity
