Needle Roller Bearings - Ntn-snr.com

Calculation of Bearing Loads
NTN
3.3 Mean load
The loads acting on bearings used in ordinary
machines fluctuate mostly depending on the
predetermined operation cycle or work plan. In such a
case, the mean load Fm converted so the same lifetime is
assigned to the bearings is used as the bearing load.
(3) Load fluctuating in nearly linear form
The mean load Fm can be determined approximately by
formula (3.14).
Fmin2Fmax
Fm
3
(3.14)
(1) Stepped fluctuating load
Where bearing loads F1 , F2 ....... Fn act on and the
rotational speed and running time are n1, n2.......nn and
t1, t2....... tn respectively, the mean load Fm of these
loads can be expressed in formula (3.12).
F
Fmax
Fm
Fi p ni ti 1p
Fm (3.12)
ni ti
Fmin
where:
p103
p3
for roller bearing
for ball bearing
Fig. 3.10 Load fluctuating in linear form
t
F
F1
F2
Fm
(4) Sinusoidal fluctuating load
The mean load Fm, can be determined approximately by
formulas (3.15), (3.16).
case of (a) Fm0.75Fmax (3.15)
case of (b) Fm0.65Fmax (3.16)
Fn
n1 t1
n2t2
nn tn
Fig. 3.8 Stepped fluctuating load
F
Fmax
(2) Consecutive series load
Where load is load cycle "to" and it can be expressed in
the function F(t) of time t, the mean load can be
expressed in formula (3.13).
1 t0 p
Fm Ftp dt
(3.13)
t0 0
F
Fm
a
t
Fmax
F
Fm
F(t)
Fm
b
t
0 to 2to t
Fig. 3.11 Sinusoidal fluctuating load
Fig. 3.9 Load fluctuating as a time function
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