The main purpose of lubrication is to minimize friction and wear between two machine parts which move relatively to each other. This is achieved by building a load-carrying lubricant film between both machine parts.
Friction conditions combined with a lubricant:
• dry friction
• mixed friction
• fluid friction
Dry friction or dry lubrication:
The load is mainly carried by the roughness peaks of both solid objects (see Fig. 11).
Mixed friction or mixed lubrication:
The load is carried by the roughness peaks and the lubricant (see Fig. 12).
Fluid friction or full fluid film lubrication:
The load is fully carried by the lubricant (see Fig. 13).