Creep is a common form of damage of rolling bearings. We need to distinguish the damage of bearing according to the specific damage of bearing and then determine how to deal with the bearing.
What is bearing creep?
Bearing creep refers to the relative sliding between mating surfaces of bearings when there is clearance.Creep with the surface showed a mirror bright or dark, sometimes with the damage caused by wear.
The creep of rolling bearings can be divided into inner ring creep and outer ring creep.
Creep of inner ring of rolling bearing means that the inner ring of the bearing is fixed with the axle through interference fit to prevent the inner ring slipping relative to the axle.However, once the proper magnitude of interference cannot be maintained, there will be a gap between the inner ring and the axle's mating surface, and the inner ring will slip relative to the axle. This phenomenon is called inner ring creep.
The creep of the outer ring of rolling bearing refers to the phenomenon that the outer ring rotates slowly relative to the bearing pedestal during the use of rolling bearing, which is called the creep of the outer ring.The creep of the outer ring will cause the wear of the bearing pedestal or outer ring and wear particles to enter the bearing, which will cause the bearing to be defective.
Influencing factors of inner ring creep of rolling bearing:
In the initial stage of inner ring creep, no sharp temperature rise was found in the bearing, and there was no direct relationship between bearing temperature rise and inner ring creep speed.At the same time, when the creep velocity of the inner ring increases to the rotating state, the wear of the matching surface of the shaft inner ring will be intensified.It is clear that the temperature of the bearing will rise due to the internal damage of the bearing, the aging of the lubrication state and the non-coincidence of the center line of the bearing when the bearing rotates in this state.
Although the bearing temperature will not rise rapidly in the initial stage of inner ring creep, with the development of creep, when the inner ring reaches the state of rotation, the data may burn out.Therefore, to prevent creep, it is very important to keep proper interference between bearing inner ring and shaft.At the same time, to prevent the bearing heat damage, the bearing temperature monitoring system with high reliability is also very important.
Factors influencing creep:
1. Temperature. As the temperature rises, the steady creep rate increases.
2. Stress, steady creep rate increases with the increase of stress,
3. Influence of microstructure, creep is a performance index sensitive to microstructure.The porosity and grain size of glass have the same effect on creep property.
Influencing factors of creep of outer ring of rolling bearing:
1. Influence of fit clearance
The creep moment calculation results of the fit clearance in the range of -30um-+30 m are shown in FIG. 1. When the fit clearance decreases, the bat moment decreases and creep becomes difficult.
2. Influence of the number of rolling objects
The influence of the number of rolling objects is shown in FIG. 2. The creep moment decreases with the increase of the number of rolling objects.This is because the load of the rolling body decreases with the increase of the number of rolling bodies, which reduces the local deformation of the outer ring.
3. Influence of outer ring wall thickness
Considering that the rigidity of the outer ring is improved to suppress the creep, the influence of the thickness of the outer ring wall (as compared with the diameter of the rolling body) is shown in FIG. 3. As the thickness of the outer ring wall increases, the creep moment decreases and the creep becomes difficult
The creep of bearing can be divided into three stages over time:
1. In initial or transitional creep, the strain increases with time, but the increasing speed gradually slows down;
2. For steady state creep or steady state creep, the strain increases uniformly with time, which is a long stage.
3. Creep is accelerated, and strain increases with time to the rupture point.The greater the stress is, the shorter the total creep time is.The less the stress, the longer the total creep time.
But every material has a minimum stress below which it will not rupture for any length of time, or creep for an infinite length of time. This stress is called the long-term strength of the material.
