COSMOS: Complete Online Solutions Manual Organization System
Chapter 9, Solution 91.
π
Ix =
From Problem 9.79:
8
π
Iy =
2
a4
1 4
a
2
I xy =
Problem 9.67:
a4
The Mohr’s circle is defined by the diameter XY, where
1
π
X a4, a4
8
2
Now
I ave =
1
1π
π 5
I x + I y = a 4 + a 4 = π a 4 = 0.98175a 4
2
2 8
2 16
(
)
2
and
R=
1
π
Y a4 , − a4
2
2
and
Ix − I y
2
+ I xy =
2
2
1 π 4 π 4
1 4
a − a + a
2
2
2 8
= 0.77264a 4
The Mohr’s circle is then drawn as shown.
tan 2θ m = −
=−
2I xy
Ix − I y
π
8
1
2 a4
2
a4 −
π
2
a4
= 0.84883
or
2θ m = 40.326°
continued
2 COSMOS: Complete Online Solutions Manual Organization System
Then
α = 90° − 40.326°
= 49.674°
β = 180° − ( 40.326° + 60° )
= 79.674°
(a)
I x′ = I ave − R cos α = 0.98175a 4 − 0.77264a 4 cos 49.674°
or I x′ = 0.482a 4
I y′ = I ave + R cos α = 0.98175a 4 + 0.77264a 4 cos 49.674°
or I y′ = 1.482a 4
I x′y′ = − R sin α = −0.77264a 4 sin 49.674°
or I x′y′ = −0.589a 4
(b)
I x′ = I ave + R cos β = 0.98175a 4 + 0.77264a 4 cos 79.674°
or I x′ = 1.120a 4
I y′ = I ave − R cos β = 0.98175a 4 − 0.77264a 4 cos 79.674°
or I y′ = 0.843a 4
I x′y′ = R sin β = 0.77264a 4 sin 79.674°
or I x′y′ = 0.760a 4
COSMOS Chapter 9 Solution 91
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