What are the damage classifications for rolling bearings?

Rolling bearing damage classification

1、Fatigue spalling Fatigue spalling is the work surface of the bearing due to rolling fatigue caused by scale-like spalling.

Rolling bearing work, rolling body and inner ring (or outer ring) by the load is not constant, but with the operation of the bearing week after week to change. This load for the alternating load; and because the rolling body and the inner ring (or outer ring) contact area is very small, making contact stress is very large, in the higher speed, in the huge alternating contact stress repeatedly under the action, the metal will occur fatigue. At first, in the stress concentration of the part of the visible tiny crack, due to the role of lubricant and metal corrosion, so that the crack gradually expanded, when expanded to a certain extent, the surface layer of metal will produce spalling, the formation of small print pits, similar to pockmark, we in the demolition inspection bearing, will often find the inner or outer ring and rolling body surface pockmark and a piece of metal spalling, which is the phenomenon of metal fatigue spalling.

Rolling bearing fatigue spalling if the bearing after a long period of operation, should be regarded as natural damage, if the use of bearings in the middle or early occurrence, should be regarded as non-natural spalling, at this time, should identify the reasons for spalling.

2、Non-natural spalling Non-natural spalling is caused by human factors occurring in the bearing use of the middle or early spalling.

The main reason for unnatural spalling is due to improper selection of bearing type or due to improper installation.

(1) due to improper selection of bearing type caused by spalling in the case of large axial load selection of deep groove ball bearings, it may occur early spalling. Flaking mainly occurs in the raceway, it makes the rolling body of the rolling track to the direction of the loading ball mouth, or even roll over the loading ball mouth, and finally make the raceway occurred serious flaking damage. Prevent this kind of damage measures is according to the bearing working conditions reasonable selection of bearings.

(2) due to improper installation caused by the spalling

(1) installation, shaft and shell of the shoulder to fit the surface is not vertical, or due to shaft bending, so that the inner and outer ring skew each other, will cause the rolling surface contact stress is too large, resulting in spalling.

(2) The outer ring is installed in the oval or conical seat hole. When the rolling body through the irregular raceway, will increase the contact stress, resulting in the raceway and rolling body early spalling.

(3) cylindrical roller bearings in the installation, due to the installation of skew and knocking when the force is too large or outer ring roller suffered injury.

(4) when the deep groove ball bearing in the shaft interference installation, if the pressure is added by the outer ring and steel ball transfer, it is inevitable in the raceway contact with the steel ball place caused by craters. These pits is the source of spalling, rapid development, will soon make the bearing scrap. Therefore, in order to overload the installation of the inner or outer ring, can only be installed on the inner or outer ring end face force.

(5) In addition, bearing installation is too tight, too loose or improperly adjusted, will also cause the early bearing stripping.

3, wear rolling bearing work, rolling body and the main movement between the raceway is rolling, rarely sliding. Therefore, under normal circumstances, the wear of bearing parts is not serious. But when the impurity invasion or poor lubrication, wear will be sharply accelerated.

(I) impurity intrusion mixed in the lubricant impurity particles (sand, dirt, etc.) into the bearing, will occur in the raceway and rolling body abrasive wear. In this case, no flaking of the metal can be seen, only uneven scratches on the working surface. Due to abrasive wear, the clearance between the inner or outer ring and the rolling body increases significantly, the raceway loses its lustre, and uneven scratches appear.

(2) Insufficient or degraded lubricating oil Insufficient or degraded lubricating oil, bearing lubrication is not guaranteed, in this case, it will lead to serious consequences. As the heat generated in the work of the bearing cannot be taken away by the lubricating oil, the bearing will lose its original mechanical properties due to overheating and the hardness will be greatly reduced, so the wear will be extremely rapid and the normal work of the bearing will be destroyed.

(3) improper use It should be pointed out that the violent wear of the bearing is mainly caused by improper use. Therefore, in the use of bearings should ensure the reliability of the installation of the bearing seal device, the working condition of the bearing and lubrication condition of the system monitoring, to ensure that the bearing in a good state of lubrication work.

4, rupture rolling bearing rupture there are two cases, one is fatigue caused by rupture, the other is improperly installed caused by rupture.

(1) fatigue caused by rolling bearing parts subjected to great alternating load. Due to the bearing material defects or other reasons, resulting in a part of the bearing stress concentration, when the stress is greater than the strength limit, the place will occur tiny crack. The continuous effect of the alternating load and the oil wedge of the lubricant, resulting in the crack constantly expanding, when the crack expands to a certain extent will occur rupture.

(2) caused by the more common cause of bearing rupture is the cause of human. Such as disassembly hard knocking and hard particles of impurities intrusion bearing internal, etc., may cause the inner and outer ring and keep frame rupture. Tapered roller bearing gap adjustment is too tight, usually in the tapered roller of the large end of the rupture; gap adjustment is too large, usually in the tapered roller of the small end of the rupture.

5, corrosion in the bearing parts surface formation of dark black spots and ulceration is the phenomenon of corrosion. Corrosion of the main reasons are:

(1) moisture or water into the bearing inside.

(2) the use of poor nature of the lubricant can also cause corrosion.

(3) there is a kind of corrosion called contact corrosion, it mainly occurs in the inner and outer ring and not rotate the rolling body of the contact surface.

6, other damage In addition to the above-mentioned kinds of damage, there are other damage.

(1) spark melt such as current through the bearing, in the raceway and rolling body contact point, the current through a very thin oil film and cause sparks, resulting in local surface melt, so that the raceway on the pit scar. These small pits due to wear and tear gradually expand, until the whole bearing damage.

(2) sliding, oxidation, grinding when the bearing does not rotate by the nearby punching machine, air compressor vibration or transport in the protection measures are not good, in the rolling body and the inner or outer ring of the question produced relatively repeated tiny sliding, so that some small particles from the surface off. These small particles once oxidation can become abrasive, accelerate the contact surface wear. Make bearing noise increases, affecting the normal work of the equipment.

(3) unreasonable design in the design of the structure of the unreasonable cause bearing damage; such as in the bearing seat with positioning screws fastened outer ring or in the bearing on the grinding groove caused by local stress concentration, so that the raceway fracture.

(4) keep frame damage keep frame due to wear, broken and broken, etc. make the bearing can not be used.

(5) residual magnetic adsorption Due to the residual magnetism caused by the adsorption of metal debris, and the bearing is damaged.