The main causes of mechanical scars of the bearing bush are: the bearing surface processing is poor, there are residual knife marks and sharp burr, the bearing alloy surface scratches when running, forming a scar; Because the lubricating oil is not pure, the impurity particles or metal chips enter the bearing gap with the lubricating oil, and will also scratch the bearing bush alloy surface to form residual scars; It is also possible that a hard foreign body is embedded on the surface of the alloy, which gradually causes the local alloy to fall off and forms spot-like scars.

In order to reduce or avoid the mechanical scars caused by the above reasons, the following preventive measures should be taken: after the surface construction of the bearing bush is completed, the grinding work should be carried out. Attention should be paid to the grinding direction to be consistent with the running direction of the shaft; Sometimes the edge of the journal oil hole is coarse, and it will scratch the bearing bush. Therefore, we should pay attention to dressing the oil hole to make it smooth; In addition, the key is to ensure that there is a clean lubricating oil, which should do two aspects of work, one in another lubricating oil, no foreign body mixed; Secondly, we should ensure that the lubricating oil filter works well, so we should clean the oil filter regularly, replace the filter element and replace the new oil regularly.

(l) Fatigue damage in the middle of the bearing bush. The cause of this damage is mostly caused by overload and bearing clearance is too large, so when using, we should pay attention to: avoid bearing overload work, do not run at too low or too high speed; The idle speed of the engine should be adjusted to a stable state without hitting the phenomenon; Ensure normal bearing clearance.

(2) Fatigue shedding. There are two reasons for this damage: one is the same as above, due to overload and bearing clearance is too large; The second is caused by overheating of bearings. To avoid fatigue shedding, ensure that the bearing clearance is normal; Prevent engine speed is too high or too low; Check and adjust the operation of the cooling system to ensure that the engine operating temperature is suitable.

(3) Other fatigue pitting. Mostly because the lubricating oil is not clean, mixed with foreign bodies and caused. Preventive measures are the same as those for mechanical scars.

Corrosion is generally caused by impure lubricating oil and chemical impurities (acidic oxides, etc.) invading into the bearing bush alloy. Oxide production is mainly the result of high temperature oxidation of the oil. When the oil temperature is lower than 150℃, the corrosion is relatively slow. In order to prevent bearing bush corrosion, the temperature of lubricating oil and cooling water should be paid attention to when using, and the engine should not work at high temperature.

Cavitation is caused by the change of lubricating oil flow rate caused by the change of rotational speed, and bubbles are produced in the oil. The pressure generated when the bubbles burst continuously impacts the alloy surface, leading to the surface damage of the alloy. This phenomenon is particularly acute at high speed and large loads.

The following four points should be paid attention to to prevent cavitation: the amount of lubricating oil should be sufficient; Oil pressure shall not be too low; When the viscosity of lubricating oil is found to decline, the lubricating oil should be replaced in time; If the water in the lubricating oil exceeds 4%, cavitation damage will be aggravated, so it is necessary to avoid the water mixed with the lubricating oil. If there is water mixed with the oil, the cause should be identified, eliminated in time, and the lubricating oil should be replaced.

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