Page 346 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
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n = 1200 r min −1 at room temperature. The external axial load acting on the gear is
F = 1000 N. Assume the load factor is f = 1.2. For designs (a) and (b), calculate
a p
the life of bearings and the ratio of bearing lives in the two designs.
e A/R ≤ e A/R > e S
0.37 X = 1, Y = 0 X = 0.4, Y = 1.6 R/2Y

(a) (b)
Figure P11.2 Illustration for Calculation Question 2.

3 A shaft is supported by a pair of 7212C bearings with the basic dynamic load rat-
ing of C = 61.0 kN, as shown in Figure P11.3. The radial loads on the bearings are
R = 640 N and R = 1965 N and the external axial load is F = 230 N. The rotational
a
2
1
speed of the shaft is 960 rpm. The bearings work at a stable loading condition and
normal temperature. Determine the life of the bearings.
Figure P11.3 Illustration for Calculation Question 3.

4 A deep-groove ball bearing 6310 with a dynamic load rating of C = 61.8 kN supports
a shaft that rotates at 1000 rpm. A uniform radial load spectrum of 3000 N, 5000 N
and 7000 N operates for 50%, 30% and 20% of the time, respectively. Estimate the life
of the bearing for a reliability of 97%.

Design Problems

1 A pair of deep-groove ball bearings carry stable radial loads of R = 5000 N and
1
R = 6000 N and an axial load of F = 2300 N, as indicated in Figure P11.4. The 60 mm
a
2
∘
diameter shaft supporting the bearings operates at a speed of 800 rpm below 100 C.
The design life is 20 000 hours. Select proper bearings for the application.
Figure P11.4 Illustration for Design Problem 1.