The calculation method of rated life is determined based on ordinary bearing steel and general working conditions, and the life reliability is 90%. Taking into account the influence of materials and use conditions and the requirements of high reliability, the International Organization for Standardization has revised the rated life formula by adding reliability coefficients, material coefficients and use condition coefficients.

    The rated life of needle roller bearings refers to the number of operations (106 revolutions) that 90% of the bearings in a batch of bearings can reach or exceed before fatigue spalling or the number of operating hours at a certain speed.

    For the basic rating life of ball bearings:

    　　L10=(Cr/Pr)3 (million revolutions)

    　　In actual calculations, the service life (hours) of the bearing is generally expressed by working hours, which is:

    　　Lh=(Cr/Pr)3/(60n)*106 (hours)

    　　 where Cr: is the basic radial dynamic load rating (KN), which refers to the imaginary constant radial load that a set of rolling bearings can withstand, and the basic rating life under this load is one million revolutions.

    　　Pr: is the radial equivalent dynamic load (KN), which refers to the radial equivalent variable load of the various external loads actually received by the bearing.

    　　For the basic rating life of roller bearings:

    　　L10=(Cr/Pr)10/3 (million revolutions)

    　　 Express the life of the bearing by working hours (hours):

    　　Lh=(Cr/Pr)10/3/(60n)*106 (hours)

    The steps for calculating the life of needle roller bearings are:

      1. According to the technical parameters of the main engine and the structure of the supporting part, the type and size of the bearing are initially selected, and the load acting on the bearing is calculated;

      2. Calculate the equivalent dynamic load;

    　　3. Calculate the life of the bearing according to the bearing rating life formula;

    　　4. Check the rated static load and limit speed.