NTN bearing fault and damage inspection attention

1. Rolling surface metal peeling
Both the NTN bearing body and the inner and outer ring raceways are subjected to periodic pulsating loads, resulting in cyclically varying contact stresses. When the number of stress cycles reaches a certain value, fatigue peeling occurs on the working surface of the body or the inner and outer ring raceways. If the load on the NTN bearing is too large, this fatigue will be exacerbated. In addition, the NTN bearing is not properly installed, the shaft is bent, and the raceway is peeled off.
Fatigue spalling of the NTN bearing raceway reduces the accuracy of the shaft and causes vibration and noise in the mechanism.
2.NTN bearing burns
The burned NTN bearing has a tempering color on the raceway and body. The causes of burns are generally insufficient lubrication, the quality of the lubricant does not meet the requirements or deterioration, and the NTN bearing assembly is too tight.
3. Plastic deformation
Uneven pits appear on the contact surface between the raceway and the roller of the NTN bearing, indicating that the NTN bearing is plastically deformed. The reason is that the NTN bearing under the action of large static load or impact load, the local stress of the working surface exceeds the yield limit of the material, which generally occurs on the NTN bearing with low speed rotation.
4.NTN bearing race crack
The cause of the crack in the NTN bearing race may be that the NTN bearing is too tight, the NTN bearing is loose in the foreign or inner ring, the NTN bearing is deformed, and the surface of the NTN bearing is poorly machined.

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6 features of sliding bearing damage

As the world's top bearing imported bearings, such as NSK bearing applications are very extensive. In every industry, the characteristics of its damage are also different. Today we look at the damage characteristics of the engine sliding bearing.
(1) Mechanical damage
The mechanical damage of the sliding bearing means that the alloy surface of the bearing bush has different degrees of groove marks. In severe cases, metal peeling occurs on the contact surface and a large area of ​​random scratches occurs; in general, the contact surface damage and ablation phenomenon exist simultaneously. The main cause of mechanical damage to the bearing is that it is difficult to form an oil film on the bearing surface or the oil film is seriously damaged.
(2), bearing cave erosion
Under the repeated action of the sliding bearing in the cylinder pressure impact load, the surface layer is plastically deformed and hardened by hardening, and the local deformation loss ability is gradually formed, and the grain is gradually formed and expanded continuously. Then, as the wear debris falls off, a hole is formed in the loaded surface layer. . Generally, when cavitation occurs in the bearing bush, the pit first appears, and then the pit gradually expands and causes cracking at the interface of the alloy layer, and the crack spreads in the parallel direction of the interface until peeling off. The main reason for the cavitation of the sliding bearing is that the oil flow is strongly disturbed due to the sudden change of the cross section of the structural elements such as the oil groove and the oil hole, and bubbles are formed in the vacuum region where the oil flow is disordered, and then the bubble collapses due to the pressure rise. eclipse. Cavitation is generally found in the high load area of ​​the bearing, such as the lower bearing of the main bearing of the crankshaft.
(3), fatigue pitting
Bearing fatigue pitting refers to the overheating of the bearing and the excessive bearing clearance due to over-loading of the engine, resulting in fatigue damage, fatigue pitting or fatigue shedding in the middle of the bearing. Most of this damage is caused by overload, excessive bearing clearance, or unclean lubricating oil and foreign matter mixed in the interior. Therefore, when using, care should be taken to avoid overloading the bearing. Do not operate at too low or too high speed; adjust the engine to a steady state when idling; ensure normal bearing clearance and prevent engine speed from being too high or too low; check and adjust cooling The working condition of the system ensures that the working temperature of the engine is suitable.

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