滚动轴承寿命计算（Rolling bearing life calculation）Rolling bearing life calculation
I. rated life and rated dynamic load
1, bearing life
Under certain loads, the number of revolutions or hours experienced by the bearing before pitting occurs is known as the bearing life.
Because of the difference in manufacturing accuracy and material uniformity, even the same material, the same size of the same batch of bearings, under the same operating conditions, the life expectancy is not the same. If statistics, the life span is 1 units, the longest relative life is 4 units, the shortest is 0.1-0.2 units, the longest and the shortest life expectancy is 20-40 times.
To determine the standard of bearing life, the bearing life is related to reliability.
2. Rated life
The same specifications (models, materials, processes) of a number of bearings in the same working conditions, 90% of the bearings do not produce pitting corrosion, the experience of revolutions or hours, known as the bearing life rating.
3 、 basic dynamic load rating
In order to compare the carrying capacity of bearings against pitting corrosion, it is stipulated that the maximum life load of the bearings is the basic rated dynamic load when the rated life of the bearings is one million RPM (106), expressed in C.
That is, bearing in the rated dynamic load C, this kind of bearing work one million turns (106) without pitting corrosion, the reliability of failure is 90%, and the larger the C, the higher the carrying capacity.
For the basic rated dynamic load
(1) radial bearings are pure radial loads
(2) thrust ball bearings refer to purely axial loads
(3) radial thrust bearings refer to radial components which produce pure radial displacement
Two. Calculation formula of bearing life:
Luoyang bearing factory takes 208 bearings as the object, carries on the massive experimental research, has established the load and the life digital relations and the curve.
In style:
reaction in the shaft
When the L10-- bearing load is P, it has the basic rated life (106 RPM)
C-- basic rated dynamic load N
Epsilon index
For ball bearings: epsilon =3
For roller bearings: epsilon =10/3
P-- equivalent dynamic load (N)
The loads in the actual conditions on the bearing: A, R, into the load under the experimental conditions is called equivalent dynamic load, the load bearing element in terms of this change, experimental research, with 106 units into the bearing life more convenient (counter), but in the production in real life as for this hour, to be converted
L10 * 106=Lh * 60N
therefore
The calculation of rolling bearing life is divided into:
1, the known bearing type, load and shaft speed, calculated Lh;
2, known load, speed and life expectancy, calculated C, select the bearing type.
Usually, the intermediate repair or overhaul limits of the machine are designed for the design life of the bearing.
Lh'=5000 is generally adopted, and the temperature coefficient ft shall be introduced for the bearings under high temperature
Ct=ftC
T = 120125150200300
FT 10.95, 0.90, 0.80, 0.60
The upper two forms become:
For centripetal bearings
For thrust bearings
Three. Calculation of equivalent dynamic load P
In practical production, the working conditions of bearings are varied. For this reason, the load under actual working conditions should be converted to the equivalent load of the same experimental load as the imaginary life.
For N0OOO, NU0OOO, NJ0OOO and NA0000, only radial load is applied: Pr = Rfp
For 51000 and 52000, only axial load is applied: Pa=Afp
For other types of bearings, 2OOOO, lOO00, 20OOO, 60000, 70000, 30000, 29000
Pr=fp (XR+YA)
In style:
R-- bearings actually carry radial loads
A-- bearings actually carry axial loads
X-- radial load factor
Y-- axial load factor
Fp-- load factor, considering the changes of load and stress, machine inertia and so on
Four. Axial load calculation of radial thrust bearing
1. pressure center
The outer ring is the intersection of the reaction line and the axis line
For thrust bearings
Formula: Dm = 0.5 (D, ten, d)
For a longer span shaft, for simplified calculation, it is assumed that the center of pressure is at the center of the bearing width.
2. axial load calculation
First introduced: bearings, bearing 13-13, b), uranium bearing reverse mounting drawing 13-13a)

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