Design of bearings

1. Journal Bearings

2. Bearing
•Bearing is a machine element that supports
•Another moving machine element i.e. journal or shaft.
• Bearing permits relative motion between members
•while carrying the load.

3. Classification of bearings
(1) Sliding contact bearings
• sliding takes place along the surfaces of contact between the moving element
and the fixed element
(2) Rolling contact bearings
• the steel balls or rollers, are interposed between the moving and fixed
elements.

4. Thin Film/ Boundary Lubrication
• Condition of lubrication
• Where lubricant film is
relatively thin
• There is partial metal to
metal contact.

5. Thick Film lubrication
• Condition of lubrication
• Where two surfaces of bearing in relative
motion
• Completely separated by a film or fluid

6. Hydrodynamic
lubrication

7. Hydrodynamic lubrication
•System of lubrication in which
•Load supporting fluid film
•Is created by
•Shape and relative motion of sliding surfaces.

8. Hydrostatic lubrication • Load supporting fluid film,
• separating two surfaces
• created by an external
source like pump.
• Externally pressurized
bearing.

9. HYDRODYNAMIC LUBRICATION

10. Raimondi Boyd Method
• In Raimondi Boyd Method, performance of hydrodynamic lubrication is
expressed in terms of dimensionless parameters.
•
• Result of their work is available in form
• of charts and tables.

11. Raimondi Boyd Method

12. Raimondi Boyd Method – Minimum oil film thickness
• Surface finish of journal and bearing is
governed by value of minimum oil film
thickness selected by designer.
• There is a lower limit for minimum oil film
thickness, below which metal to metal
contact occurs and hydrodynamic film
breaks.
•This lower limit is :

13. Raimondi Boyd Method – Sommerfeld Number

14. Raimondi Boyd Method – Frictional Power

15. Raimondi Boyd Method – Flow Variable

16. Raimondi Boyd Method – Temperature Rise

17. Raimondi Boyd Method – Temperature Rise

18. Raimondi Boyd Method – Temperature Rise