Correct Answer - Option 3 : hydrodynamic
Concept:
Hydrodynamic Lubrication:
- It is thick film lubrication in which fluid pressure is created by the relative motion between the moving parts.
- As fluid pressure is itself being created, there is no need for a pressurized supply of lubricant.
- In this, surfaces do not contact during the rotation as there is a thick film of the lubricant.
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It can be used with thrust as well as sliding contact bearing.
Hydrostatic lubrication:
- In hydrostatic lubrication, external pressure is supplied to separate two surfaces, while relative velocity between two surfaces is used to generate liquid pressure between two surfaces.
- Hydrostatic lubrication is generally costlier compared to hydrodynamic lubrication.
Boundary Lubrication:
- With the lower relative velocity of the moving surfaces, adequate pressure cannot be developed to support the load by the oil film. At this point of time, boundary lubrication will exist. This will occur especially during starting and stopping of an engine.
- As the speed increases, sufficient film pressure is developed, and the load is supported by the oil film and this will shift to the hydrodynamic lubrication.
Mixed/ Partial Lubrication:
- Mixed lubrication, in which part of the interface pressure is carried by asperity contact and part by the pressurized lubricant film in the surface valleys is the preferred lubrication regime in many production metal forming operations.
- Mixed lubrication provides the opportunity to suppress or reduce surface roughening without the high levels of friction and potential for lubrication breakdown associated with operating in the boundary regime.
