1. Peeling off at the extreme position on one side of the channel
The spalling at the extreme position of one side of the channel is mainly manifested in the severe spalling ring at the junction of the channel and the rib. The cause is that the bearing is not installed in place or there is a sudden axial overload during operation.
The countermeasures taken are to ensure that the bearing is installed in place or to change the outer ring fit of the free side bearing to a clearance fit, so that the bearing can be compensated when the bearing is overloaded. If it cannot be ensured that the installation is in place, you can increase the oil film thickness of the lubricant (increase 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 peeling shows that the inner ring is peeling off around the circumference, while the outer ring is peeling off in a circumferential symmetrical position (that is, the short axis direction of the ellipse). The main reason is that the ellipse of the shell hole is too large or the two-half separated shell hole structure. This is particularly evident in motorcycle camshaft bearings. When the bearing is pressed into a housing hole with a larger ellipse or the two halves of the separate housing are tightened, an ellipse is formed in the outer ring of the bearing, and the clearance in the short axis direction is significantly reduced or even negative. Under the action of load, the inner ring of the bearing will rotate and produce circumferential peeling marks, while the outer ring will only produce peeling marks at a symmetrical position in the short axis direction. This is the main reason for the early failure of the bearing. The inspection of the failed parts of the bearing shows that the outer diameter roundness of the bearing has changed from 0.8um controlled by the original process to 27um. This value is much larger than the radial clearance value. Therefore, it can be determined that the bearing is operating under severe deformation and negative clearance, and it is easy to cause abnormal and rapid wear and peeling on the working surface in the early stage.
The countermeasures taken are to improve the processing accuracy of the housing hole or to avoid using the two-half separation structure of the housing hole as much as possible.
3. The raceway is tilted and peeled off
The appearance of an inclined peeling ring on the working surface of the bearing indicates that the bearing is working in an inclined state. When the inclination angle reaches or exceeds the critical state, abnormal and rapid wear and peeling may occur early. The main reasons are poor installation, deflection of the shaft, low accuracy of the journal and housing hole, etc.
Countermeasures are taken to ensure the bearing installation quality and improve the axial runout accuracy of the shaft shoulder and hole shoulder, or to increase the viscosity of the lubricating oil to obtain a thicker lubricating oil film.
4. The ferrule is broken
Ring breakage failure is relatively rare and is usually caused by sudden overload. The causes are complex, 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, instantaneous overload), etc. Excessive impact load or severe vibration may cause the ferrule to break.
The countermeasures taken are to avoid overload impact loads, select appropriate interference, improve installation accuracy, improve usage conditions and strengthen quality control in the bearing manufacturing process.
5. The cage is broken
Cage fracture is an occasional abnormal failure mode. The main reasons are as follows:
a. Abnormal load on the cage. If the installation is not in place, tilted, or the interference is too large, it will easily lead to reduced clearance, aggravated friction and heat generation, surface softening, and premature and abnormal peeling. As the spalling expands, the spalled foreign matter enters the pockets of the cage, causing the cage to run blocked and generate additional loads, aggravating the wear of the cage. Such worsening circulation may cause the cage to break.
b. Poor lubrication mainly means that the bearing is running in an oil-lean state, which is prone to adhesive wear, deteriorating the condition of the working surface, and the tears caused by adhesive wear are easy to enter the cage, causing the cage to generate abnormal loads and possibly causing the cage to break.
c. The intrusion of foreign matter is a common mode of cage fracture failure. Due to the intrusion of foreign hard foreign matter, the wear of the cage is aggravated and abnormal additional loads are generated, which may also cause the cage to break.
d. Creep phenomenon is also one of the causes of cage fracture. The so-called creep refers to the sliding phenomenon of ferrules. When the interference of the mating surface is insufficient, the load point moves in the peripheral direction due to sliding, causing the ferrule to deviate in the circumferential direction relative to the shaft or housing. Once creep occurs, the mating surface will wear significantly, and wear powder may enter the inside of the bearing, causing abnormal wear - raceway peeling - cage wear and additional load, which may even cause the cage to break.
e. Cage material defects (such as cracks, large foreign metal inclusions, shrinkage holes, air bubbles) and riveting defects (missing nails, pad nails or gaps between the two cage halves, serious riveting damage) may cause the retaining The frame breaks.
The countermeasure is to strictly control the manufacturing process.
6. stuck injury
The so-called seizure is the surface damage caused by the aggregation of micro burns on the part where the damage occurred on the sliding surface. Linear scars on the circumference of the slideway surface and rolling surface. Cycloidal scars on the end faces of the rollers, seizures on the collar surfaces near the end faces of the rollers. The main causes of jamming include: excessive load, excessive preload, poor lubrication, bite-in of foreign matter, tilt of the inner and outer rings, deflection of the shaft, poor accuracy of the shaft and bearing box, etc.
It can be solved by proper preloading, improving lubricant and lubrication method, and improving the precision of shaft and bearing housing.
7. Wear and tear
Abrasion failure refers to the failure caused by the relative sliding friction between the surfaces that leads to the continuous wear of the metal on the working surface. The main factors causing wear failure are lubricant failure or lack of lubricant, wrong lubrication method, abrasive particles entering the bearing, excessive load, etc. The solution can be to improve the lubricant or improve the lubrication method, strengthen the sealing mechanism, etc.
8. Abrasions
The so-called scuffing refers to the surface damage that occurs on the raceway surface and rolling surface due to the accumulation of micro burns caused by rolling slippage and thermal cracking of the oil film. Produces a rough surface with stickiness. The main causes of scratches are high-speed light load, rapid acceleration and deceleration, improper lubricant, water intrusion, etc.
Solution: improve preload, improve bearing clearance, use lubricant with good oil film property, improve lubrication method, improve sealing device, etc.
9. Indentation
When small metal powder or foreign matter bites into the rolling element, dents are produced on the raceway surface or rotating surface, or concave surfaces (Brnell hardness indentations) are formed on the spacing intervals of the rolling elements due to impact during installation. The main factors that cause indentation are: metal powder and other foreign matter biting, excessive impact load during assembly or transportation, etc.
Solution: improve the sealing device, filter lubricating oil, improve assembly and use methods, etc.
10. Burns
Raceways, rolling elements and cages heat up rapidly during rotation until they become discolored, softened, welded and damaged. The causes of burns include poor lubrication, excessive load (excessive preload), excessive rotation speed, too small clearance, intrusion of water and foreign matter, poor accuracy of the shaft and bearing box, large shaft deflection, etc.
It can be solved by improving lubricants and lubrication methods, correcting bearing selection, studying fit, bearing clearance and preload, improving sealing devices, checking the accuracy of shafts and bearing boxes, or improving installation methods.
11. Galvanic corrosion
The so-called electric corrosion means that when electric current flows in the contact part of the rotating bearing ring and the rolling element, sparks are 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 effect of static electricity.
Solution: When setting the circuit, the current does not pass through the bearing, the bearing is insulated, and the static is grounded.
12. Rust and corrosion
Bearing rust and corrosion include pit rust on the surface of raceways and rolling elements, and comprehensive rust and corrosion. Rust and corrosion of bearings will cause pit rust on the surface of rings and rolling elements, pear-shaped rust and pit rust with the same spacing between rolling elements, and overall rust and corrosion. There are many reasons for the rust, corrosion and failure of rolling bearings. The main reasons are: intrusion of water and corrosive substances (paint, gas, etc.), inappropriate lubricants, water droplets attached due to condensation of water vapor, stalling when high temperature and humidity, transportation process Poor rust prevention, inappropriate storage conditions, inappropriate use, etc.
The solutions include: improving sealing devices, studying lubrication methods, anti-rust measures when stopping, improving storage methods, and paying attention when using them.
In addition to the above common failure modes, there are many failure modes of rolling bearings in actual operation, which await our further analysis and research. To sum up, it can be seen from the common failure mechanisms and failure modes of bearings that although rolling bearings are precise and reliable structural foundations, improper use can also cause early failure.
Generally speaking, if the bearings are used correctly, they can be used until their fatigue life. Early failure of bearings is mostly caused by factors such as the manufacturing accuracy of the host's mating parts, installation quality, usage conditions, lubrication effect, intrusion of external foreign matter, thermal impact, and sudden failure of the host.
Therefore, the correct and reasonable use of bearings is a systematic project. In the process of bearing structure design, manufacturing and installation, taking corresponding measures for the links that cause early failure can effectively improve the service life of bearings and main engines.