How to use FAG bearings to improve shaft support rigidity

The FAG bearing pre-tightening method can be used to improve the bearing rigidity. The ball bearing or the tapered roller bearing can adopt the axial pre-tightening method, and the short cylindrical roller bearing can adopt the radial pre-tightening method, which can significantly improve the rigidity of the shaft bearing. At the same time, the bearing clearance is eliminated or a small negative clearance is obtained. However, under the condition that the rotation speed is not too high and the temperature rise is not large, it is better to adjust to a small negative clearance state. When preloading is applied, the deformation should be continuously measured. Note that in the low value stage of deformation, the deformation is nonlinear with the increase of the preloading load; in the high value stage, the deformation is linear with the increase of the load.

Once the deformation-load has a linear relationship, the pre-tensioning load is stopped immediately, and a constant stiffness is obtained. Thereafter, there is a fixed relationship between the axial stiffness and the radial stiffness of the bearing, independent of the applied load.

The above-mentioned deformation amount can be measured by, for example, abutting the dial gauge against an appropriate end portion of the bearing end face or the shaft, and observing the change of the reading with the preload load. The pre-tightening method has its disadvantages, such as increasing the friction torque of the FAG bearing, increasing the temperature rise, shortening the life, etc., so it is necessary to comprehensively consider the trade-offs and gain the appropriate pre-tightening amount.

The configuration of the bearing arrangement of the bearing has a great influence on the bearing rigidity. Generally speaking, for the ball thrust bearing and the roller bearing of the centripetal thrust type, it is preferable to adopt the large end face of the outer ring when paired (ie, the pressure line is formed). The configuration of the pressure cone tip outwards is such that the FAG bearing has a large ability to resist the overturning moment, and the amount of preload that is adjusted when the temperature changes is less changed.

Multi-bearing support is adopted. Under the condition that the axial position allows, two or more bearings are used as radial support for each fulcrum, which can improve the support rigidity. For example, in the recent spindle parts of machine tools, a plurality of sets of radial thrust bearings mounted axially preloaded as shaft supports of the same fulcrum are widely used.

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Turntable bearing maintenance precautions

1. When cleaning and removing the slewing bearing, first take a look at the appearance with photography. Also, verify the amount of lubricant remaining and sample the lubricant before cleaning the bearings.

a. The cleaning of the bearing is carried out by rough washing and fine washing, and a metal mesh frame can be placed on the bottom of the used container.

b. When rough washing, remove the grease or adhesive with a brush or the like in the oil. At this time, if the bearing is rotated in the oil, be careful that the rolling surface will be damaged by foreign matter or the like.

c. When washing finely, slowly rotate the bearing in the oil and carry out it carefully. The cleaning agent generally used is a neutral non-aqueous diesel oil or kerosene, and a warm alkali liquid or the like is sometimes used as needed. Regardless of which cleaning agent is used, it is often filtered and kept clean. Immediately after cleaning, apply anti-rust oil or anti-rust grease to the bearing.

2, inspection and judgment

In order to judge whether the removed bearing can be reused, it is important to check its dimensional accuracy, rotation accuracy, internal clearance, mating surface, raceway surface, cage and seal. Regarding the inspection result, it can be judged by a person who is using a conventional bearing or a proficient bearing.

The criteria for judgment vary depending on mechanical properties and importance, inspection period, and the like.

Bearings must not be reused if they are damaged and must be replaced.

a, the fracture and defects of the bearing components.

b. Peeling of the rolling surface of the raceway surface.
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Bearing material and structure for slurry pump

When the shaft rotates, the low temperature liquid outside the bearing is sucked into the bearing by the screw action and the pressure difference between the two ends of the bearing. After the bearing is lubricated and cooled, it flows into the teeth which are just disengaged to form a spiral with sufficient lubrication and fast heat dissipation. Self-priming low pressure lubrication system. The advantage of this lubrication method is that the lubricating fluid entering the bearing is all low-temperature medium, and the viscous lubricating fluid is easy to form a dynamic pressure oil film with strong bearing capacity. A large amount of lubricating fluid circulation continuously removes the heat of the bearing and provides good lubrication and cooling for the bearing. Since there is sufficient liquid to fill the root of the gear that has just been disengaged, the self-priming performance of the gear pump is greatly improved, and the suction phenomenon is avoided, which not only improves the volumetric efficiency, but also reduces cavitation and reduces noise. The design institute uses the sliding bearing to be immersed in the medium and forced lubrication through special holes. This technology has been successfully applied in gear pumps in the fields of vinyl, polyester, rubber, resin and fertilizer.

The material of the bearing is usually made of tool steel and is surface hardened to improve its resistance to gluing. If the conveying medium contains abrasive particles, a very hard bearing material such as ceramics should be used. In recent years, GS-1 polytetrafluoroethylene steel composites have been considered as ideal sliding bearing materials.

It is composed of a cold-rolled steel sheet (base), a sintered spherical porous bronze powder or a copper mesh (intermediate layer), and a polytetrafluoroethylene (surface layer) three-layer material, which combines the advantages of metal and polytetrafluoroethylene plastic. Based on this material, the Institute developed a SF-type three-layer composite self-lubricating material with better performance. It replaced the bronze powder layer with a bronze wire mesh, and the plastic formula of the surface layer was carefully selected. The bearing material has the advantages of fatigue resistance, high bearing capacity, small friction coefficient and long service life, and is a novel bearing material for improving the technical performance of the gear pump.
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Factors affecting the service life of rolling bearings

The performance of rolling bearings has a major impact on the performance of mechanical systems. However, there are many factors affecting the fatigue life of rolling bearings, such as working temperature, impact load, reliability, materials, operating conditions, limit speed, surface roughness, inclusions, indentation, lubrication. State, radial clearance, deflection, fatigue crack induced stress, tangential friction, residual stress and hoop stress, surface treatment, etc. These factors affect each other, combined with the non-repetition of fatigue life test, the influencing factors are still difficult to be accurate Quantitative description.

Rolling bearing fatigue life The classic L-P theory is based on the assumption that the fatigue failure of a rolling contact originates from the depth at which the orthogonal shear stress is greatest at the contact area. However, with the development of the bearing manufacturing process, the fatigue failure mode originating from the surface appears more frequently than the subsurface fatigue failure mode. There are three mechanisms for crack initiation: crack initiation from the surface, crack initiation from the near surface, and crack initiation in the material matrix.

The puncture life originating from the surface and the spalling life of the subsurface origin are competing failure modes, which are predicted as a function of the film thickness ratio, the root mean square value of the slope of the rough peak, and the traction coefficient in the rough contact of the boundary lubrication.

With the development of high-speed railway and aviation industry, there are more and more requirements for high reliability of bearings, and the temperature of bearing application environment changes greatly. It is necessary to study the coupling between reliability and temperature. Rolling bearing materials are still in development. It is necessary to explore the relationship between the surface integrity of the parts and the surface fatigue pitting. On the microscopic scale, the effects of surface integrity and lubrication effects on the fatigue pitting point are revealed. On the other hand, combined with the load characteristics and the dynamic response of the material to study the spalling failure, analyze the dynamic response of the bearing material to the external load, study the coupling relationship between fatigue performance and material properties, and obtain the relationship between the dynamic response of the material and the surface fatigue spalling.

For other factors affecting bearing fatigue life, such as lubricants and additives, surface roughness, hoop stress and interfacial slip, etc., comprehensive research is also needed, such as the establishment of databases and R&D software packages for automated analysis of lubricants and bearing materials. With choice, this is also one of the future directions.

Analysis of the factors affecting the rolling failure of the bearing helps to better understand the mechanism of bearing fatigue failure. On the one hand, it can avoid the factors that reduce the bearing life and improve the fatigue life of the bearing; on the other hand, it can provide some guidance for the development of fatigue life theory, in order to improve the accuracy of bearing fatigue life prediction.
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