Bearing steel under the combined effect of complex factors, the bearing is destroyed after a considerable period of operation.
ISUTAMI believes that there are two main forms of destruction:
One is contact fatigue failure. Under the action of high contact stress, after repeated stress cycles, pits are generated in the local area of the working surface, so that the noise increases when the bearing works, the vibration is enhanced, the temperature rises, and the wear is intensified. The bearing does not work properly.
The other is wear and tear caused by relative activities. The normal form of failure of rolling bearings is usually fatigue spalling.
Fatigue failure of bearing steel includes two processes of generation and development of fatigue cracks.
The initial fatigue crack is generated at a certain depth from the surface, which is exactly the same as the depth of the maximum shear stress. For bearings of normal size, the maximum shear stress should occur somewhere between 0.35 and 0.55 mm of the contact surface, depending on the load.
The metal in this area first undergoes plastic deformation under the action of maximum shear stress. If the contact stress is greater than the contact fatigue limit of the material, as the number of stress cycles increases, the plastic deformation has been continuously plastically deformed, and fatigue cracking cannot be performed here due to plastic deformation.
Under normal conditions, the microcracks are at an angle of approximately 45° on the surface. The fatigue spalling crack on the contact track of the rolling bearing gradually expands under the action of repeated stress, and usually develops along the inner structure and the composition of the material and the uneven distribution of the stress until it extends to the surface, and breaks from the root of the crack to form fatigue spalling.