Causes and solutions of fatigue damage of the hott

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Causes and solutions of bearing fatigue damage:

1. Analysis of bearing fatigue damage phenomenon:

1. The length of the period during which the first material fatigue phenomenon of the bearing occurs from the beginning of use is related to the speed of the bearing, the size of the load, and the degree of lubrication cleanliness

2. Fatigue is the result of the periodic occurrence of shear stress under the load surface. After a period of time, these shear stresses will cause small cracks, and then gradually extend to the surface. When the rolling parts pass through these cracks, some cracks will fall off, forming the so-called "peeling phenomenon". Then as the peeling continues to expand, the bearing will be damaged and unusable

3. The above is the description of bearing fatigue, which initially occurred below the surface. Although the initial peeling is usually very slight, with the increase of stress and the increase of cracks, the peeling area spreads. Although the overall level of plastic materials used in China's automobile manufacturing industry has not reached the world's leading level, the bad situation usually remains for a long time, The obvious visible stage is when the noise and vibration increase

4. At the initial stage of damage, the bicycle bearing may only be difficult to feel when rotating, but later it is found that there is a pitting feeling when rotating. Once there is a pitting feeling, the bearing is not unusable, but there is greater wear and more serious damage to the beads, shaft bowl and shaft stop every time. Because the bicycle is a low-speed high extreme pressure type of bearing, even if the surface peeling phenomenon is serious, It's not unusable, but it consumes your power silently, and your feeling may just be that the car doesn't know why it's not easy to ride

5. Therefore, before the bearing is completely damaged, it provides users with enough time to find out. Don't ignore the existence of this friction, which will reduce the speed of riding, and make the consumption of physical strength for long distance greater and slower

if the roughness of the surface is fine, and the lubricating oil film has an appropriate thickness, the probability of surface stress generation is quite low, which is why it is necessary to properly select the appropriate oil for lubrication. However, if the pressure load exceeds the Pu value of the oil film (fatigue (4) check whether the fuse on the machine socket burns out the limit value of labor load, such as too high speed, too high pressure impact), The fatigue of the material will come sooner or later

II. Causes of bearing damage and solutions:

1. Causes of bearing damage in advance - (improper lubrication)

although "maintenance free" rubber sealed bearings can be installed, 36% of bearings that fail in advance are still caused by incorrect application of grease technology

any bearing with improper lubrication will inevitably fail in advance. Because the bearing is the part in the flower drum where the glue is not easy to assemble and disassemble, and the incorrect grease is used congenital, and the grease is not replaced in the later use, or it is not replaced in time after the grease is carbonized, deteriorated and polluted, then it is difficult for your flower drum to have a long enough life and good lubrication

for bicycles, we now encounter small-scale bearings that are mostly deep groove balls, such as 609600060016200, which are used in industry for the stator and rotor of small-scale motors, and such small-scale motors are usually pre loaded with low viscosity, high lubricity broad-spectrum grease

in the past, we used to buy and use a large number of expensive greases. For example, we used to buy SKF lgmt-2 synthetic lithium grease, which is a small motor lubricant with low torque and low friction. It was also used in most small SKF Peilin. At that time, the price was still very expensive. The packaging price of 200g was as high as more than 60 yuan, but the viscosity of such oil was only 110. For high load and extreme pressure, The ability of reciprocating motion is poor. According to the use of the bicycle shaft, this should be a kind of low speed, high extreme pressure (because a large amount of pressure is only concentrated on a few small pears, and greater pressure will be generated during impact jumping), so we later chose SKF lgep-2 to form lithium base grease. Although this kind of grease is also expensive (155 yuan), its viscosity reaches 200, high load, high water resistance, high rust resistance, and high grade 6 earthquake resistance, Although it is not as good as lgmt-2 in terms of low torque friction index, it is completely suitable for the front and rear middle axles of bicycles and the first bowl group of bicycles (today we use lgep-2 lubrication in the repair of some old flower drums, such as RM40)

2. The reason why the bearing was damaged in advance - (improper assembly)

another reason for the damage of up to 16% is that the improper assembly and the wrong or violent loading method have made those Peilin have already suffered from the percussion injury on the surface of the smooth bell bowl when loading

in order to make Peilin clamp the shaft axis tightly and prevent the shaft sleeve friction phenomenon (this phenomenon will instantly produce high temperature on the high-speed rotating machinery, causing the lubricating oil to burn dry and even cause the heat rise to jam, resulting in shutdown), so the inner bell and outer bowl of the bearing (also known as the bearing box in industry) use a kind of "interference" phenomenon, which means that the shaft is larger than the inner bell, or the outer bowl is larger than the load, This interference requires a lot of force to install, and such installation requires a lot of force to knock Peilin, which will cause damage to Peilin in the process of knocking. Therefore, large bearings in industry usually adopt heating, hydraulic jacking and other methods

bicycles use rubber 2. Standard 220V power supply and power supply system sealed deep groove ball bearings. Such bearings are most afraid of percussion (needle roller Peilin and big Peilin have a slightly stronger resistance to percussion), and heating loading method cannot be used. However, because the interference of bicycle Peilin is very small, even if Qinghao Peilin flower drum can be put into Peilin by hand, it is relatively safe to use rubber hammer for percussion, However, the jacking backing material needs a very flat surface, and static pressing, such as vise pressing, is the best way

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