Application of Probability to Mechanical Design
81
Stress relief by grooves or tapering
Figure 2.20 Various assemblies of collars shrunk on a shaft.
EXAMPLE.
Table 2.10
where
Straight shaft of steel with surface rolling find Cv~f
~f= 1+~= 1.5
kfmi,d = 1 +.~(1 --3Cry)= 1 +0.5(1 -310.21)=
kfmax ~ 1 +~(1 + 3Cry) = 1 +0.5(1 + 3[0.2]) =
Since 1 variable is used as a card sort and the range is six standard deviations
6~f = kfmax - kmin
1.8- 1.2 0.6
~f
6 --6
Cvkj
~f 0.1 × 100 = 6.67%
(2.75)
7. Internal Structure, kg
For the purposes of this book the only internal structural aspects of fatigue
behavior of materials of interest are inclusions that act as stress concentrators and (probably related to inclusions) directional effects giving rise
to different fatigue properties in the longitudinal and transverse directions of
fabricated materials. By longitudinal is meant the axis of rolling direction in
sheet, for example. More will be said about this later in the design application examples where it is pointed out that the transverse fatigue properties
of many steels, for example, are distinctly lower than the longitudinal
fatigue properties. Here much data is required. Generally kg= 1, C~
undefined, ~g = 0.