NOTE: ALL NOTATION ACCORDING TO FIGURE
Concept:
Initially when jouranal is at rest , bearing load keeps the journal to make contact with inner part of the housing.
When journal starts rotation at low speed condition in anticlockwise direction as shown in figure . The friction force between journal and bushing will be in opposite direction of movement so orientatian of jouranal to bush have inclined angle of friction
**by this designer can determine the minimum oil film thickness location**
If bearing works at low speed for long time metal to metal contact will present for long time so bearing will fail after some revolution that is why not preffered at low speed condition.
When shaft rotates at high speed, lubricant oil will get some velocity and finally converging to diverging zone is developed and lubricant zone is start to move in this zone. due to this positive wedge pressure profile is generated which bear the load .
When lubricant move A-B-C in converging zone velocity of lubricant increases and pressure of lubricant decreases
When moving from D-E-A in diverging zone velocity of lubricant decreases and pressur of lubricant increases due to this positive pressure profile is generated .
If the load is too large or Shaft rotation is low or Viscosity of lubricant is low , then wedge like shape will not form( i.e no converging diverging zone is formed) and finnally metal to metal contact will occur
0 comments:
Post a Comment