Common failure modes and countermeasures of rolling bearings
1. One-sided extreme position peeling of the channel
The one-side extreme position spalling of the channel is mainly manifested by a severe spalling band at the interface between the channel and the rib. The cause is that the bearing is not installed properly or there is a sudden axial overload during operation.
The countermeasures taken are to ensure that the bearing is installed in place or that the free-side bearing outer ring fits into a clearance fit, so that the bearing is compensated when the bearing is overloaded. If it is not possible to ensure that the installation is in place, you can increase the oil film thickness of the lubricant (improve the viscosity of the lubricant), or reduce the load on the bearing to reduce the direct contact of the bearing.
2. The channel peels off in a symmetrical position in the circumferential direction
The symmetrical position spalling shows that the inner ring is spalled around the inner ring, and the outer ring is peeled off in a circumferentially symmetric position (ie, the short axis direction of the ellipse), mainly because the outer hole ellipse is too large or the two halves are separated from the outer hole structure. It is particularly evident in camshaft bearings for motorcycles. When the bearing is pressed into the outer shell hole of the elliptical ellipse or the two halves are fastened, the outer ring of the bearing is elliptical, and the clearance in the short axis direction is significantly reduced or even negative. Under the action of the load, the inner ring rotates to produce circumferential peeling marks, and the outer ring only produces peeling marks at the symmetrical position in the short axis direction. This is the main reason for the early failure of the bearing. After testing the failure of the bearing, the roundness of the outer diameter of the bearing has changed from 0.8um to 27um. This value is much larger than the radial clearance value. Therefore, it can be confirmed that the bearing is working under severe deformation and negative play, and it is easy to form abnormal sharp wear and peeling at the early stage.
The countermeasures taken are to improve the machining accuracy of the outer casing hole or to use the two-half separation structure of the outer casing hole as much as possible.
3. The raceway is peeling off
The inclined spalling belt on the bearing working surface indicates that the bearing is working under the inclined state. When the inclination angle reaches or exceeds the critical state, it is easy to form abnormal sharp wear and peeling at an early stage. The cause is mainly due to poor installation, shaft deflection, low precision of the journal and housing bore.
Take measures to ensure the quality of the bearing installation and improve the axial runout accuracy of the shoulders and shoulders, or increase the viscosity of the lubricant to obtain a thicker lubricant film.
4. Ferrule break
Fracture failure of the ferrule is relatively rare, usually caused by sudden overload. The causes are more complicated, such as bearing raw material defects (bubble shrinkage), forging defects (overburning), heat treatment defects (overheating), processing defects (local burns or surface microcracks), host defects (poor installation, poor lubrication, transient Overload) and so on. It is possible to break the ferrule by overload shock load or severe vibration.
The countermeasures taken are to avoid overload shock loads, select appropriate interference, improve installation accuracy, improve operating conditions and enhance quality control during bearing manufacturing.
5. Cage breakage
Cage breakage is an accidental abnormal failure mode. There are five main reasons for this:
a. Abnormal load on the cage. If the installation is not in place, the inclination, the interference is too large, etc., the play is reduced, the friction heat is increased, the surface is softened, and the abnormal peeling occurs prematurely. As the exfoliation expands, the exfoliation of foreign matter enters the pocket of the cage, causing the cage to stall and generate additional loads, which exacerbates the wear of the cage, and the deterioration of the circulation may cause the cage to break.
b. Poor lubrication mainly means that the bearing is running in a lean state, which is easy to form adhesive wear, which deteriorates the working surface condition. The tearing material generated by adhesive wear easily enters the cage, causing abnormal load on the cage, which may cause the cage to break.
c. The intrusion of foreign objects is a common mode of failure of the cage. Due to the intrusion of foreign hard foreign objects, the wear of the cage is increased and an abnormal additional load is generated, which may also cause the cage to break.
d. Creep is also one of the causes of cage breakage. The sliding phenomenon of the creeping multi-finger ferrule, when the interference of the mating surface is insufficient, the load point moves in the peripheral direction due to the sliding, and the ferrule is displaced from the axis or the outer casing in the circumferential direction. Once the creep is generated, the mating surface is significantly worn, and the wear powder may enter the inside of the bearing, forming an abnormal wear--the process of the flake peeling-cage wear and the additional load, which may cause the cage to break.
e. Retainer material defects (such as cracks, large foreign metal inclusions, shrinkage cavities, air bubbles) and riveting defects (nails, studs or two-half cage joint surface voids, severe riveting) may cause retention The frame is broken.
Take countermeasures to strictly control the manufacturing process.
6. Card injury
The card-injury is a surface damage caused by a combination of minute burns in a portion of the sliding surface damage. Linear scratches on the surface of the slideway and the circumferential surface of the rolling surface. A pendulum-like flaw on the end face of the roller and a jam on the collar face near the end face of the roller. The main causes of the card injury are: excessive load, excessive preload, poor lubrication, foreign matter biting, inclination of the inner ring outer ring, shaft deflection, shaft and bearing box accuracy.
It can be solved by properly pre-pressing, improving the lubricant and lubrication method, and improving the accuracy of the shaft and bearing housing.
Wear failure refers to the failure of the relative sliding friction between the surfaces resulting in the continuous wear of the metal on the working surface. The main factors causing wear and tear are lubricant failure or lack of lubricant. The lubrication method is not correct. There are abrasive grains entering the bearing and the load is too large. The solution can be enhanced by improving the lubricant or improving the lubrication method.
The so-called abrasion is a surface damage which occurs on the raceway surface and the rolling surface with a summary of minute burns caused by rolling slip and oil film thermal cracking. Produces a rough surface with adhesion. The main causes of abrasions are high-speed light load, rapid acceleration and deceleration, improper lubricant, and water intrusion.
Solution: Improve preload, improve bearing clearance, use oil film lubricant, improve lubrication method, and improve sealing device.
When a small metal powder or foreign matter is bitten, a dent formed on the raceway surface or the rotating surface or a shock due to the installation causes a concave surface (Brinell hardness indentation) at a pitch interval of the rolling elements. The main factors causing the indentation are: foreign matter such as metal powder biting, excessive impact load during assembly or transportation.
Solution: Improve the sealing device, filter the lubricant, improve the assembly and use methods.
The raceways, rolling elements, and cages rapidly heat up during rotation until discoloration, softening, welding, and breakage. The causes of burns are poor lubrication, excessive load (pre-pressure is too large), excessive speed, too small clearance, intrusion of water and foreign matter, poor precision of the shaft and bearing housing, and large deflection of the shaft.
It can be solved by improving the lubricant and lubrication method, correcting the choice of bearings, researching the fit, bearing clearance and preload, improving the sealing device, checking the accuracy of the shaft and bearing housing or improving the installation method.
11. Current corrosion
The so-called electric erosion means that when a current flows in the rotating contact portion of the bearing ring and the rolling element, a spark is emitted through the thin lubricating oil film, and local melting and unevenness appear on the surface. The main cause of galvanic corrosion is the potential difference between the outer ring and the inner ring and the action of static electricity.
Solution: When setting the circuit, the current does not pass through the bearing, the bearing is insulated, and the static ground.
12. Rusty corrosion
The rust and corrosion of the bearings have raceways, pit rust on the surface of the rolling elements, and overall rust and corrosion. The rust and corrosion of the bearing will cause the pit rust on the surface of the ferrule and the rolling element, the pit-like rust and the same crater rust, full rust and corrosion. There are many reasons for the failure of rolling bearing rust corrosion, mainly: intrusion of water, corrosive substances (lacquer, gas, etc.), improper lubricant, water droplets due to condensation of water vapor, stop at high temperature and humidity, transportation process The rust prevention is poor, the storage state is not suitable, and the use is not suitable.
The solutions are: improving the sealing device, studying the lubrication method, anti-rust measures when stopping, improving the storage method, and paying attention when using it.
Reprinted from the network