13_ch 11 Mechanical Design budynas_SM_ch11 - 3 3(10 6 = 8...

Chapter 11
301
We can calculate ( C
10
)
m
by similar triangles.
log( C
10
)
m
− log 18
log 43 . 2 − log 1
=
log 39 . 6 − log 18
log 13 . 8 − log 1
log( C
10
)
m
=
log 43 . 2
log 13 . 8
log
39 . 6
18
+ log 18
( C
10
)
m
= 55 . 8 kN
The usefulness of this plot is evident. The improvement is 43 . 2 / 13 . 8 = 3 . 13 fold in life.
This result is also available by ( L
10
)
m
/ ( L
10
)
1
as 360 / 115 or 3.13 fold, but the plot shows
the improvement is for all loading. Thus, the manufacturer’s assertion that there is at least
a 3-fold increase in life has been demonstrated by the sample data given. Ans.
11-18 Express Eq. (11-1) as
F
a
1
L
1
= C
a
10
L
10
= K
For a ball bearing, a = 3 and for a 02-30 mm angular contact bearing, C
10
= 20 . 3 kN.
K = (20