Main forms and causes of failure of rolling bearings
Rolling bearings in the running process may be due to various reasons causing damage, such as improper assembly, lubrication, moisture and foreign material intrusion, corrosion and overload can lead to premature bearing damage. Even after the installation, lubrication and use of maintenance are normal, after a period of operation, the bearing will appear fatigue spalling and wear and can not work. In short, rolling bearing fault reason is very complex. The main failure forms of rolling bearings and the reasons are as follows.
1 fatigue spalling
Rolling bearings in the inner and outer rolling and rolling surfaces are subjected to load and relative rolling, due to the role of alternating load, first in the surface of a certain depth (maximum shear stress) to form a crack, and then extended to the surface of the contact surface to make the surface spalling, and finally developed to large spalling, this phenomenon is fatigue spalling. Fatigue spalling can cause impact load, vibration and noise in the running. Usually, fatigue spalling is often the main reason for the failure of rolling bearings, the general said that the bearing life is the fatigue life of bearing, bearing life test is fatigue test. Test procedure, in the rolling or rolling body appear on the area of 0.5mm2 of the fatigue spalling pit that bearing life end. The fatigue life of rolling bearings is very large. The maximum service life and the lowest life span of the same batch of bearings are the highest. The importance of fault monitoring of rolling bearing is explained from another point of view.
Due to the intrusion of dust, foreign body, raceway and rolling body relative motion will cause surface wear and lubrication will aggravate the wear, the wear results the bearing clearance increases and surface roughness is increased, reducing the running accuracy of bearing and thus reduce the motion accuracy of the machine, vibration and noise also increases. For precision mechanical bearings, it is often the amount of wear that limits the life of the bearing.
In addition, there is a micro vibration wear. In the case that the bearing is not rotated, due to the action of the vibration, the rolling element and the rolling contact surface have small, repeated relative sliding and wear.
3 plastic deformation
When the axial subjected to impact load or static load, or because of the additional load caused by thermal deformation, or have very high hardness of foreign intrusion when will in the raceway surface form dents or scratches. This will cause the bearing in the running process to produce violent vibration and noise. Once there is an indentation, the impact load caused by indentation will further cause the surface to be peeled off.
Corrosion is one of the most serious problems of rolling bearings, high precision bearings may be due to the loss of accuracy caused by surface rust and can not continue to work. Water or acid, alkaline material directly into the human will cause bearing corrosion. When the bearing to stop working, the bearing temperature dropped to the dew point, the air in the water condensation into the water droplets attached on the surface of the bearing can also cause corrosion. In addition, when the current through the bearing internal, current may through the raceway and rolling body at the contact point, a thin film of oil caused by electric spark generated electrical erosion. On the surface the formation of washboard is uneven.
High load may cause the bearing part fracture. Grinding, heat treatment and assembly will cause the residual stress, the thermal stress will cause the bearing part fracture. In addition, the assembly method, improper assembly process, may also cause the bearing ring rib and roller chamfer off block.
In poor lubrication, high speed and heavy load case work and heat due to friction, bearing parts can be in a very short period of time to reach a high temperature, resulting in surface burns and gluing. The so-called glue is a part of the surface of the metal on the surface of the metal adhesion to another part of the surface phenomenon.
7 cage damage
Due to the improper assembly or use may cause the holder to deformation, increase the friction between it and the rolling body, and even some of the rolling body stuck can not roll, but also may cause the cage and the inner and outer ring friction, etc.. This damage will further make the vibration, noise and heat increased, resulting in bearing damage.