Rolling bearing load and life

The total number of revolutions before contact fatigue wear or the total number of working hours at a certain speed in any component of the rolling bearing is called the bearing life of the rolling bearing. The life of the same batch of bearings is running under the same conditions. Can be several times or even tens of times. 90% of the same batch of bearings is called the rated life L when the total number of revolutions (or working hours) that can be reached or exceeded before fatigue spalling. The load that can be withstood at a rated life of 1 million rpm is the rated dynamic load C. When the sum of the plastic deformation of the contact between the rolling element and the raceway with the largest load reaches one ten thousandth of the rolling element diameter, the load that can be withstood is the rated static load C0. The greater the rated load, the stronger the load capacity of the bearing. The rated load of the radial bearing is a pure radial load, and the rated load of the thrust bearing is a pure axial load. The actual load condition of the bearing is often different from the rated load and must be converted into equivalent load. Under the action of the equivalent dynamic load P, the life of the bearing is the same as the life under the actual load condition. Under the action of the equivalent static load P0, the total plastic deformation at the contact of the rolling element and the raceway with the largest load is the same as that under the actual load condition. The relationship between the rated life of the bearing, the rated dynamic load and the equivalent dynamic load is the formula ε is the life index: ball bearing ε=3, roller bearing ε=10/3. When selecting a bearing, the repair or overhaul period of the machine is usually taken as the expected life of the bearing. For example, the equipment that is not used frequently is 500 to 2000 hours; the machine that is used continuously for 8 hours per day is 20,000 to 30,000 hours; the machine that continuously uses 24 hours per day is 4 to 100,000 hours. In fact, only a few bearings are damaged when the life expectancy is reached.

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Failure classification of imported bearings

Related content of imported bearings) Abrasive wear refers to the wear of external hard particles or hard foreign matter or metal surface between the working surface of the imported bearing bearing and the relative movement of the contact surface, often causing plowing on the bearing working surface. Grooved bruises. Hard particles or foreign matter may come from inside the host or from other adjacent parts of the host system and be fed into the bearing by the lubricating medium. Adhesive wear refers to uneven friction of the friction surface due to microscopic protrusions or foreign matter on the friction surface. When the lubrication condition is seriously deteriorated, local friction occurs due to local friction, which may cause local deformation of the friction surface and friction micro-welding phenomenon. When the surface metal may be partially melted, the force on the contact surface tears the local friction weld from the substrate to increase the plastic deformation. This adhesive-tear-adhesive cycle constitutes adhesive wear. In general, slight adhesive wear is called abrasion, and severe adhesive wear is called bite.

The main cause of fracture failure of imported bearing bearings is the two major factors of defects and overload. When the applied load exceeds the material strength limit and the part is broken, it is called overload fracture. The main reason for the overload is the sudden failure of the host or improper installation. Defects such as microcracks, shrinkage cavities, air bubbles, large foreign objects, overheated tissue and localized burns of the bearing parts also cause breakage at the defects during impact overload or severe vibration, called defect fracture. It should be pointed out that in the manufacturing process, in the process of re-inspection of raw materials, quality control of forging and heat treatment, and process control, the above defects can be correctly analyzed by instruments, and control must be strengthened in the future. However, in general, most of the bearing fracture failures that occur are overload failures.

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