Application of Probability to Mechanical Design
97
(~’r
0 -o
m
~ult
O" m
Figure 2.35 Fatigue curve construction.
4. Fatigue curves with the established method of using a factor of
safety
(3-4) - ductile materials
(5-6) - brittle materials
with a R(0.99) can also be drawn on or-am curve Fi g. 2. 15 with
many designs checked this way.
The conditions 1,2, 3 are ideal for computer or handwritten solutions, when
the a’r/a’,, , design line is known. Note in Fig. 2.35
O" r
-- = zero
thus ayt or autt is the intersection on the am line
O" m
a’r _ infinite
so 8e is the intersection on the or line
O’rn
The equations for a one dimensional overlap calculation can be used by
setting the pf
1
1
Pf =~-~g or 10
~
for a one sided distribution curve.
Pf = 9.8659 x 10
-1°
for z = -6 standard deviations
1
109
97
(~’r
0 -o
m
~ult
O" m
Figure 2.35 Fatigue curve construction.
4. Fatigue curves with the established method of using a factor of
safety
(3-4) - ductile materials
(5-6) - brittle materials
with a R(0.99) can also be drawn on or-am curve Fi g. 2. 15 with
many designs checked this way.
The conditions 1,2, 3 are ideal for computer or handwritten solutions, when
the a’r/a’,, , design line is known. Note in Fig. 2.35
O" r
-- = zero
thus ayt or autt is the intersection on the am line
O" m
a’r _ infinite
so 8e is the intersection on the or line
O’rn
The equations for a one dimensional overlap calculation can be used by
setting the pf
1
1
Pf =~-~g or 10
~
for a one sided distribution curve.
Pf = 9.8659 x 10
-1°
for z = -6 standard deviations
1
109