The installation and adjustment of low-noise bearings can also follow the grouping method of long-life bearings, so that the matching interference is relatively uniform, the bearing clearance is also consistent, and it is hoped that the interference will take a smaller value within the possible range to ensure The deformation of the bearing race is small, so that the noise caused by the passage of the rolling elements becomes small.
The clearance has a great relationship to noise. The ideal state is that the clearance value is just zero when the bearing is in the highest temperature state of operation. The method for judging the excessive clearance is that the static state causes the shaft to be axially displaced, and the reciprocating amplitude thereof is large, and large and heavy turbid noise is emitted during operation.
If an annoying and screaming sound is heard during operation, the pre-tightening of the bearing is too large, and the bearing has a large pre-interference, and the pre-tightening degree should be slightly relaxed. If the clearance is too large, the two bearing rings can be slightly offset in the axial direction: the clearance is reduced, the axial rigidity is increased, and the bearing noise can be reduced.
When the rolling element enters the no-load zone, it will slip or make a left and right sway, which will increase the noise and cause wear, while the small clearance and large axial stiffness can eliminate this phenomenon. However, the play should not be too small to avoid excessive temperature and shortened life.
Sometimes due to the large operating temperature range of the main engine, or the large dispersion of the shaft and the seat hole, it is impossible to obtain a proper clearance at a time. In this case, the outer ring of the bearing can be elastically pressurized. Tight method.
2018年11月30日星期五
2018年11月28日星期三
What are the characteristics and uses of roller bearings?
The rolling elements of the roller bearings are radial rolling bearings of cylindrical rollers. Cylindrical rollers and raceways are line contact bearings. Load capacity, mainly bear radial load. The rolling element has little friction with the ferrule rib and is suitable for high speed rotation. According to the ferrule with or without ribs, there are single row bearings such as NU, NJ, NUP, N, NF, and double row bearings of NNU and NN. The bearing is a structure in which the inner ring and the outer ring are separable. Cylindrical roller bearings with no ribs on the inner or outer ring, the inner and outer rings can move relative to the axial direction, so they can be used as free end bearings. A cylindrical roller bearing with a single rib on one side of the inner and outer rings and a single rib on the other side can withstand a certain degree of axial load in one direction. Steel stamping cages or copper alloy cages are generally used. However, some use polyamide shaped cages.
What are the characteristics and uses of roller bearings?
1: The roller and the raceway are in line contact or repaired line contact, and have a large radial load capacity, which is suitable for those subjected to heavy load and impact load.
2: The friction coefficient is small, suitable for those high speeds, and the limit speed is close to the deep groove ball bearing.
3: N-type and NU-type can move axially, can adapt to the change of the relative position of the shaft and the shell caused by thermal expansion or installation error, and can be used as a free end support.
4: The machining requirements for the shaft or the seat hole are relatively high, and the relative deflection of the outer ring axis after the bearing is installed must be strictly controlled to avoid contact stress concentration.
5: The inner ring or the outer ring can be separated to facilitate the installation and disassembly of the bearing.
The main uses are: large and medium-sized motors, rolling stock, machine tool spindles, internal combustion engines, generators, gas turbines, gearboxes, rolling mills, vibrating screens, and lifting and transporting machinery.
Both ball bearings and roller bearings are rolling bearings. The simplest one is that the rolling elements are balls, which are steel balls. The other rolling element is a steel column.
http://www.bearingkingdom.com/roller-bearings/
What are the characteristics and uses of roller bearings?
1: The roller and the raceway are in line contact or repaired line contact, and have a large radial load capacity, which is suitable for those subjected to heavy load and impact load.
2: The friction coefficient is small, suitable for those high speeds, and the limit speed is close to the deep groove ball bearing.
3: N-type and NU-type can move axially, can adapt to the change of the relative position of the shaft and the shell caused by thermal expansion or installation error, and can be used as a free end support.
4: The machining requirements for the shaft or the seat hole are relatively high, and the relative deflection of the outer ring axis after the bearing is installed must be strictly controlled to avoid contact stress concentration.
5: The inner ring or the outer ring can be separated to facilitate the installation and disassembly of the bearing.
The main uses are: large and medium-sized motors, rolling stock, machine tool spindles, internal combustion engines, generators, gas turbines, gearboxes, rolling mills, vibrating screens, and lifting and transporting machinery.
Both ball bearings and roller bearings are rolling bearings. The simplest one is that the rolling elements are balls, which are steel balls. The other rolling element is a steel column.
http://www.bearingkingdom.com/roller-bearings/
2018年11月26日星期一
Magnetic Particle Inspection and Failure Analysis of Common Defects in Bearings
Magnetic Particle Inspection and Failure Analysis of Common Defects in Bearings
Due to the irregularity of the cutting, burrs, flashing, etc., it is easy to form a fold on the surface, which is characterized by a coarse folding, an irregular shape, and easy to appear on the surface of the part.
It is best to use fluorescent magnetic powder for flaw detection to make the defect display clearer and more intuitive. The forged folded magnetic marks are generally linear, grooved and scaly in shape at an angle to the surface.
The defect cross section was made into a metallographic sample and observed under a microscope. The defect tail was blunt, smooth on both sides, and there was obvious oxidation. As shown in Fig. 2, no foreign matter such as material inclusions were found in the defect. After cold metal corrosion, metallographic samples were observed, the defects and their sides were severely decarburized and oxidized. The surface morphology of the defect delamination was observed, and the plastic deformation marks were obvious, and there was no tear-like fracture morphology. After the microhardness test and metallographic observation, there are different degrees of carburization and hardening on the surface of the defect layer. In summary, it shows that the defect should exist before the heat treatment quenching, and communicate with the outside world to determine that the defect is forged folding.
The forging heating temperature is too high, the holding time is too long to produce overheating, and in the severe case, the grain boundary is oxidized or even melted. In the microscopic observation, not only the surface layer of the metal layer is oxidized and cracked, but also the sharp corners are formed. Moreover, in the region where the internal component of the metal is segregated, the grain boundary begins to melt, and in severe cases, a sharp-angled cavern is formed. The over-fired material is forged in such a defect state, subjected to forging, punching, and grinding of the weight, where the defect is torn and a larger defect is formed. Forging severely over-fired surface forms such as orange peel with fine cracks and thick scales.
Fluorescent magnetic powder should be used for flaw detection to make the defect display clearer. The pitting hole is caused by the forging burn defect.
The metallographic specimens taken along the defect section were observed under the microscope. It can be seen that the pores are distributed on the surface and the subsurface. The localities are sharp-angled, different in size, deep in the bottom, and there are fine cracks on the edges. Some areas have appeared. The grain boundary oxidation phenomenon, the pore morphology is shown in Figure 4. Another fracture hole was observed along the defect hole, and the fracture surface was observed. The fracture was a stone-like fracture, and a large number of holes and fine cracks were distributed thereon.
Due to the irregularity of the cutting, burrs, flashing, etc., it is easy to form a fold on the surface, which is characterized by a coarse folding, an irregular shape, and easy to appear on the surface of the part.
It is best to use fluorescent magnetic powder for flaw detection to make the defect display clearer and more intuitive. The forged folded magnetic marks are generally linear, grooved and scaly in shape at an angle to the surface.
The defect cross section was made into a metallographic sample and observed under a microscope. The defect tail was blunt, smooth on both sides, and there was obvious oxidation. As shown in Fig. 2, no foreign matter such as material inclusions were found in the defect. After cold metal corrosion, metallographic samples were observed, the defects and their sides were severely decarburized and oxidized. The surface morphology of the defect delamination was observed, and the plastic deformation marks were obvious, and there was no tear-like fracture morphology. After the microhardness test and metallographic observation, there are different degrees of carburization and hardening on the surface of the defect layer. In summary, it shows that the defect should exist before the heat treatment quenching, and communicate with the outside world to determine that the defect is forged folding.
The forging heating temperature is too high, the holding time is too long to produce overheating, and in the severe case, the grain boundary is oxidized or even melted. In the microscopic observation, not only the surface layer of the metal layer is oxidized and cracked, but also the sharp corners are formed. Moreover, in the region where the internal component of the metal is segregated, the grain boundary begins to melt, and in severe cases, a sharp-angled cavern is formed. The over-fired material is forged in such a defect state, subjected to forging, punching, and grinding of the weight, where the defect is torn and a larger defect is formed. Forging severely over-fired surface forms such as orange peel with fine cracks and thick scales.
Fluorescent magnetic powder should be used for flaw detection to make the defect display clearer. The pitting hole is caused by the forging burn defect.
The metallographic specimens taken along the defect section were observed under the microscope. It can be seen that the pores are distributed on the surface and the subsurface. The localities are sharp-angled, different in size, deep in the bottom, and there are fine cracks on the edges. Some areas have appeared. The grain boundary oxidation phenomenon, the pore morphology is shown in Figure 4. Another fracture hole was observed along the defect hole, and the fracture surface was observed. The fracture was a stone-like fracture, and a large number of holes and fine cracks were distributed thereon.
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