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Basic Rated Dynamic Load And Rated Life Of NACHI Precision Bearings
Oct 22, 2018

NACHI precision bearings have the following requirements: large load capacity, small friction, smooth rotation, quiet, high precision, rigidity, etc. These functions must be kept at the same time. These functions are called bearing durability (grease life, sound life, fatigue life, etc.) that is, life in a broad sense. However, durability will affect its sustainability due to various damage and deterioration. In addition, there are other damages such as cracking, bite sticking and so on will also affect the bearing life, but these damages should be distinguished from the bearing life. The causes of these damages, in addition to bearing selection errors, but also include bearing peripheral design and the use and installation of bearings and other factors.

On the other hand, the repeated stress caused by load will cause damage to the bearing material itself due to rolling fatigue. Even if the bearing is used correctly, it will eventually reach the bearing life in a narrow sense. Generally speaking, once there are signs of metal fatigue, it can be immediately judged that the bearing can not continue to use, by this time the life of the bearing will be at an end. The life of a bearing can be expressed by the total number of rotations from the beginning of the bearing operation or by the total running time of the bearing at a given speed. Even under the same load condition, the life of the bearing varies according to the size and type of the bearing used. When bearing is selected, bearing life should be recalculated. Bearing fatigue life (narrow sense life) Originally each bearing has its own differences, usually described by a set of identical bearings under the same conditions of the operation of statistical results. Therefore, when choosing bearings, the calculated life of bearings can not be understood as the average life of all bearings, only can be understood as the expected life of most of the NACHI bearings can be reached before it is more practical.

Therefore, we define the rated life and the basic rated load Cr or Ca as follows. Basic rated life A group of identical bearings operate under the same conditions, 90% of which can rotate the total number of revolutions without material damage due to rolling fatigue. Basic rated dynamic load (Cr or Ca) can reach bearing life of 1 million revolutions in the direction and size of the same bearing load. The basic rated life of the bearing is calculated according to formula 2.1 and 2.2. (Formula 2.1) (Formula 2.2) L: Basic Rating Life (Rotation) Lh: Basic Rating Life (Hour) C: Basic Rating Dynamic Load (N) (when the radial bearing is Cr, when the thrust bearing is Ca) P: Bearing Load (equivalent dynamic load) (N) (when the radial load is Pr, when the thrust bearing is Pa) p: 3 (ball bearing) 10/3 (roller bearing) N: Speed: min - 1) The basic rated dynamic loads of radial ball bearings are calculated by multiplying the rated dynamic loads of single row bearings by the following coefficients. The 2 columns are matched with 3 columns, 4 sets and 1.62 2.16 2.64.