Bearings are commonly used parts in various machines, equipment, instruments and meters, and are widely used in industrial and agricultural production and national defense construction. No matter in the fields of automobile, light textile, ship, radar, motor, rolling stock, or mining, metallurgy, petrochemical, agriculture, household appliances, IT, etc., wherever there is rotary motion, bearings are inseparable.
The good or bad performance of bearings also determines the working condition of instruments, meters and equipment, especially the technical level and quality of rolling bearings, which directly affects the working performance, service life and various economic indicators of the working host. As the bearing failure, mainly occurs in its work surface and near the surface layer, fatigue crack sprouting and expansion is also mostly concentrated in the work surface and surface layer.
With the continuous development of modern industry, the number and scale of bearings and their derivatives are so large. Bearings are mainly divided into rolling bearings and sliding bearings, and the specific classification mainly includes radial bearings, thrust bearings, liquid-lubricated bearings, incomplete liquid-lubricated bearings, non-lubricated bearings, spherical ball bearings, spherical roller bearings, tapered roller bearings, double-row deep groove ball bearings, thrust ball bearings, deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, needle roller bearings and so on.
According to statistics, there are more than 3000 bearing parts in a modern aircraft. Deep groove ball bearing as a rolling bearing in the most common type of structure, the basic type by the outer ring, inner ring, ball and cage composition, mainly used to bear pure radial load, but also can simultaneously withstand radial load and axial load.
Fatigue damage will occur in rolling bearings under repeated loads, and about 80% of structural strength damage in modern industry is caused by fatigue damage. If the bearings are well lubricated, properly installed, no axis deflection, no pollution particles and impurities, and moderate load, the bearing damage is only caused by fatigue of the material. Bearing damage occurs mainly on the contact surface and near contact surface layer, and the fatigue crack generation and expansion are mostly concentrated in this area. Once the bearing damage occurs, the noise and vibration deteriorate sharply, resulting in the bearing not working properly, and the corresponding rolling bearing life means the bearing fatigue life.
In order to avoid fatigue damage, for many years people have been committed to bearing materials, design, manufacturing and lubrication technology research, required in the geometry and size of the case, improve the comprehensive performance of the bearing work surface, especially the contact fatigue resistance. Many factors affect bearing fatigue life, clearance, boundary lubrication, contact surface deformation, materials, mechanical processing methods and heat treatment process methods, the environment and the impact of temperature.
High temperature can have a significant impact on the normal operation of the bearing. For bearings, high temperature will lead to a rapid reduction in clearance and a rapid increase in contact stress, so the phenomenon of frictional heat generation will also be very serious.
At present, it is generally believed that the bearing fatigue failure is mainly divided into two kinds: (1) the most important one is most of the bearing parts appear peeling small pits (pitting), the depth and in the rolling direction measured contact surface width is the same order of magnitude. After the formation of pitting, under the load, the metal particles edge of the chipped mouth, and pitting along the rolling direction with the trend of continuous expansion, the result of the bearing can not be used.