What are the damage classifications of rolling bearings?

1. Fatigue spalling fatigue spalling is the flaky spalling of the working surface of the bearing caused by rolling fatigue.
When the rolling bearing works, the load on the rolling body and the inner ring (or outer ring) is not constant, but changes with the running of the bearing. This kind of load is alternating load; And because the contact area between the rolling body and the inner ring (or outer ring) is very small, the contact stress is very large. Under the action of the huge alternating contact stress many times at a high speed, fatigue will occur in the metal. At the beginning, small cracks are visible in the stress concentration parts, due to the role of lubricating oil and metal corrosion, so that cracks gradually expand, when expanded to a certain extent, the surface metal will produce spalling, forming a small imprint pit, similar to pitting, we in the dismantling of bearings, will often find the inner or outer ring and rolling body surface pitting and a piece of metal spalling, This is the phenomenon of metal fatigue flaking.
If the fatigue spalling of the rolling bearing occurs after the bearing runs for a long time, it should be regarded as natural damage. If it occurs in the middle or early stage of the bearing's use, it should be regarded as unnatural spalling. At this time, the cause of spalling should be identified.
2. Unnatural peeling is the peeling of bearings caused by human factors in the middle or early stage of use.
The main cause of unnatural spalling is due to improper bearing type selection or improper installation.
(1) Because of the spalling caused by the improper selection of bearing type, early spalling may occur when deep groove ball bearings are selected under the condition of large axial load. Spalling mainly occurs in the raceway, which makes the rolling track of the rolling body move to the direction of the ball loading port, or even roll over the ball loading port, and finally causes serious spalling damage to the raceway. The measure to prevent this damage is to choose bearings reasonably according to the working conditions of bearings.
(2) spalling caused by improper installation
1) When installing, the shoulder of the shaft and the shell are not perpendicular to the surface, or because the shaft is bent, the inner and outer rings are skewed to each other, which will cause excessive contact stress on the rolling surface, leading to spalling.
2) The outer ring is installed in the oval or conical seat hole. When the rolling body passes through the irregular raceway, the contact stress will be increased, resulting in early spalling of the raceway and rolling body.
3) Cylindrical roller bearings are injured during installation due to skew installation and excessive force when knocking on the inner or outer ring.
4) When the deep groove ball bearing is installed on the shaft interference, if the added pressure is transmitted through the outer ring and the steel ball, it will inevitably cause pits at the place where the raceway contacts the steel ball. These pits are the source of peeling, rapid development, will soon make the bearing scrap. Therefore, when the inner or outer ring is installed with interference, only the inner or outer ring end face can be installed.
5) In addition, too tight, too loose or improperly adjusted bearings will also cause early spalling of bearings.
3, wear rolling bearing work, the main movement between the rolling body and raceway is rolling, rarely sliding. Therefore, under normal circumstances, the wear of bearing parts is not serious. But when impurities invade or lubrication is poor, wear will accelerate dramatically.
(I) The intrusion of impurity particles (sand, dirt, etc.) mixed in the lubricating oil into the bearing, abrasive wear will occur on the raceway and rolling body. In this case, no peeling of metal is visible, just 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 luster, and uneven scratches appear.
(2) Insufficient lubricating oil or deterioration When insufficient lubricating oil or lubricating oil deterioration, bearing lubrication can not be guaranteed, in this case, it will lead to serious consequences. Because the heat generated in the work of bearings can not be taken away through the lubricating oil, the bearings will lose their original mechanical properties due to overheating, and the hardness is greatly reduced, so the wear is extremely rapid, destroying the normal work of bearings.
(3) improper use should point out that the intense wear of bearings is mainly caused by improper use. Therefore, the reliability of the installation of the bearing seal device should be ensured in the use of bearings, and the working condition and lubrication condition of bearings should be systematically monitored to ensure that bearings work in good lubrication condition.
4. There are two kinds of rupture of rolling bearing, one is the rupture caused by fatigue, the other is the rupture caused by improper installation.
(1) Rolling bearing parts caused by fatigue bear great alternating load. Because of the material defect of the bearing or other reasons, the stress concentration occurs in a certain part of the bearing. When the stress is greater than the strength limit, a small crack will occur there. The continuous action of alternating load and the wedge action of lubricating oil cause the crack to expand continuously, and when the crack expands to a certain extent, it will crack.
(2) Man-made causes of bearing breakage are more common. Such as hard knock and hard particle impurities invade the bearing inside when disassembling and assembling, may cause the inner and outer rings and cages to crack. Taper roller bearing clearance adjustment is too tight, usually in the big end of the taper roller rupture; The clearance adjustment is too large, usually at the small end of the conical roller rupture.