2019年8月28日星期三

Engine sliding SKF bearing damage features

Core Tip: As the world's top bearing SKF bearings, the application is 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
As the world's top bearing SKF bearings, the application is 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.

(4), bearing alloy corrosion

The bearing alloy corrosion is generally the area where the lubricating oil is not pure. The chemical impurities (acid oxides, etc.) in the lubricating oil cause the bearing alloy to oxidize to form an acidic substance, causing the bearing alloy to partially fall off and form irregular micro holes or small concaves. pit. The main reason for the corrosion of the bearing alloy is improper selection of lubricating oil, poor corrosion resistance of the bearing material, or rough engine operation and high temperature.
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Preparation for lathe SKF bearing installation

Core Tip: It is often the case that some friends use improper methods when installing SKF bearings, resulting in damage to SKF bearings during installation. Today, I will tell you about the lathe SKF bearing before installation.
It is often the case that some friends use improper methods when installing SKF bearings, resulting in damage to the SKF bearings during installation. Today I will tell you about the preparations for the installation of the SKF bearing on the lathe. I hope everyone has to help.

For the correct installation method of SKF bearings, please refer to the article "Introduction to the installation method of SKF bearings".

1. Selection and requirements for the installation site

The installation site should be at a distance from the lathe, grinder and other mechanical equipment. The site should be cleaned and kept dry and clean to prevent iron filings, sand, dust and moisture from entering the bearing.

2. Check the bearing model and prepare the installation tool

Verify that the bearing type and size meet the installation requirements, and select the appropriate assembly method according to the structural characteristics of the bearing and the various components that match it, and prepare the tools and gauges for installation. Commonly used installation tools include hand hammers, copper rods, sleeves, special pads, screw-mosquito fixtures, presses, etc., with vernier calipers, micrometers, dial gauges, etc.

3. Verify the bearing assembly surface

The surface of the bearing assembly and the surface of the part with which it is fitted, if there is a bump, rust layer, wear debris, sand, dust and dirt, one bearing is difficult to install, resulting in incorrect assembly position; second, these attachments form abrasive, easy Abrasive damage to the working surface of the bearing, affecting the quality of the assembly. Therefore, the surface of the journal, the surface of the housing hole, the end surface of the shoulder, and the mating surfaces of the connecting parts such as bushings, washers, end caps, etc., should be carefully inspected before installation. If there is a rust layer, it can be finely smashed, and the fine sand cloth is used to illuminate, and at the same time, the attachment surface of the bearing assembly and the attached parts thereof are also removed.
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