1、 Mechanical damage
In severe cases, metal peeling and large-area messy scratches occur on the touch surface; Under normal circumstances, mechanical damage of bearing refers to that the alloy surface of bearing bush presents groove marks at different levels. The primary reason of bearing mechanical damage is that the bearing surface is difficult to form oil film or the oil film is severely damaged.
2、 Bearing cavitation
The surface layer has plastic deformation and cold work hardening, and the sliding bearing is under the repeated effect of cylinder pressure impact load. Part of the loss of deformation ability gradually forms a pattern and expands, and then with the falling of wear debris, the loaded surface layer forms a cavity. Usually, when the bearing bush has pitting corrosion, it first presents pits, and then the pits gradually expand and lead to the cracking of the alloy layer interface. The cracks expand along the parallel direction of the interface until the falling stops. The primary reason for the cavitation of sliding bearing is that the sudden change of the cross section of layout elements such as oil groove and oil hole leads to the intense imbalance of oil flow. The vacuum area of oil flow imbalance forms bubbles, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of the bearing, such as the lower bearing shell of the crankshaft main bearing.
3、 Fatigue pitting
Because the engine is overloaded, bearing fatigue and pitting refers to. The bearing operation is overheated and the bearing gap is too large, which constitutes fatigue damage, fatigue pitting corrosion or fatigue falling in the middle of the bearing. This kind of damage is mostly caused by overload, too large bearing gap, maybe the smooth oil is not clean and there are foreign matters in it. Therefore, when using, we should pay attention to avoid bearing overload operation, and do not operate at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure normal bearing clearance and avoid too high or too low engine speed; Check and adjust the operation of the cooling system to ensure 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 acidic substances. The corrosion area of the bearing alloy is usually the impure smooth oil. Cause the alloy part of the bearing to fall, forming irregular small cracks or pits. The main reasons for bearing alloy corrosion are improper selection of smooth oil, poor corrosion resistance of bearing materials, rough engine operation and high temperature.
5、 Bearing melting
The component is at high temperature, and there is a small raised metal surface between the journal and the bearing pair. In case of lack of smoothness and poor cooling, the bearing alloy will be blackened or partially melted. This problem is often caused by too tight cooperation between journal and bearing; The lack of smooth oil pressure also simply burns the bearings.
In severe cases, metal peeling and large-area messy scratches occur on the touch surface; Under normal circumstances, mechanical damage of bearing refers to that the alloy surface of bearing bush presents groove marks at different levels. The primary reason of bearing mechanical damage is that the bearing surface is difficult to form oil film or the oil film is severely damaged.
2、 Bearing cavitation
The surface layer has plastic deformation and cold work hardening, and the sliding bearing is under the repeated effect of cylinder pressure impact load. Part of the loss of deformation ability gradually forms a pattern and expands, and then with the falling of wear debris, the loaded surface layer forms a cavity. Usually, when the bearing bush has pitting corrosion, it first presents pits, and then the pits gradually expand and lead to the cracking of the alloy layer interface. The cracks expand along the parallel direction of the interface until the falling stops. The primary reason for the cavitation of sliding bearing is that the sudden change of the cross section of layout elements such as oil groove and oil hole leads to the intense imbalance of oil flow. The vacuum area of oil flow imbalance forms bubbles, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of the bearing, such as the lower bearing shell of the crankshaft main bearing.
3、 Fatigue pitting
Because the engine is overloaded, bearing fatigue and pitting refers to. The bearing operation is overheated and the bearing gap is too large, which constitutes fatigue damage, fatigue pitting corrosion or fatigue falling in the middle of the bearing. This kind of damage is mostly caused by overload, too large bearing gap, maybe the smooth oil is not clean and there are foreign matters in it. Therefore, when using, we should pay attention to avoid bearing overload operation, and do not operate at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure normal bearing clearance and avoid too high or too low engine speed; Check and adjust the operation of the cooling system to ensure 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 acidic substances. The corrosion area of the bearing alloy is usually the impure smooth oil. Cause the alloy part of the bearing to fall, forming irregular small cracks or pits. The main reasons for bearing alloy corrosion are improper selection of smooth oil, poor corrosion resistance of bearing materials, rough engine operation and high temperature.
5、 Bearing melting
The component is at high temperature, and there is a small raised metal surface between the journal and the bearing pair. In case of lack of smoothness and poor cooling, the bearing alloy will be blackened or partially melted. This problem is often caused by too tight cooperation between journal and bearing; The lack of smooth oil pressure also simply burns the bearings.
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