Five considerations in bearing operation
In severe cases, metal peeling occurs on the touch surface and a large area of messy scratches; in general, mechanical damage of the bearing means that the alloy surface of the bearing bush exhibits a different level of groove marks. The first cause of the mechanical damage of the bearing caused by the touch surface damage and the ablation surface is that the bearing surface is difficult to form an oil film or the oil film is severely damaged.
2. Bearing cavitation
The surface layer is plastically deformed and hardened by cold work, and the sliding bearing is subjected to the repeated effect of the cylinder pressure shock load. Part of the loss of deformation ability, and gradually form the pattern and continue to expand, and then followed by the falling of the grinding debris, the surface layer of the loaded surface constitutes a hole. Usually, when the bearing is cavitation, the pit is firstly formed, and then the pit is gradually enlarged and causes cracking at the interface of the alloy layer, and the crack expands in the parallel direction of the interface until the drop stops. The primary cause of the cavitation of the sliding bearing is that the oil flow is fiercely disordered due to the cross-section of the layout elements such as the oil groove and the oil hole. The vacuum zone of the oil loss adjusts to form a bubble, and then the bubble collapses due to the pressure rise. Cavitation is usually found in the high load area of the bearing, such as the lower bearing of the main bearing of the crankshaft.
3. Weak pitting
Because the engine is overloaded, the bearing is weak and pitting. The bearing operation is overheated and the bearing clearance is too large, which constitutes fatigue damage in the middle of the bearing, fatigue and pitting may be exhausted. Most of this damage is caused by overload, excessive bearing clearance, and perhaps the smooth oil is not clean and the inside is mixed with foreign matter. Therefore, the application should focus on avoiding overloading of bearings. Do not operate at too low or too high speed; adjust the engine to a stable condition when idling; ensure normal bearing clearance, avoid excessive or too low engine speed; view and adjust cooling The operation of the system ensures that the operating temperature of the engine is suitable.
4. Bearing alloy corrosion
The chemical impurities (acid oxides, etc.) in the smooth oil oxidize the bearing alloy to form an acidic substance, and the bearing alloy corrosion is usually a smooth oil impure. This causes the bearing alloy to partially fall, forming irregular small holes or small pits. The primary cause of corrosion of bearing alloys is the improper selection of smooth oil, poor corrosion resistance of bearing materials, and perhaps rough engine operation and high temperature.
5. Bearing melting
The part is high temperature, and there is a small convex metal surface straight touch between the journal and the bearing conflicting pair. In the case of lack of smoothness and poor cooling, the bearing alloy is blackened or partially melted. This problem is often caused by the cooperation of the journal and the bearing too tight; the lack of smooth oil pressure also makes the bearing burned.
Reprinted from the network