Exam II
•
this Friday 2pm (March 28)
•
In classroom
DCC 324
!!!
•
Covers Chapters 46 (L9L15)
•
1 page crib sheet double sided (no
workedout problems)
•
4 problems
•
Sample exam posted on blackboard
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•
Estimate stress graphically using Mohr’s circle
•
For a known state of plane stress
 plot center (
σ
ave
)

plot point X (
σ
x
,
τ
xy
)
 plot point Y (
σ
y
,
τ
xy
)
 connect X and Y through C
2
2
2
2
x
y
x
y
ave
xy
R
σ
σ
σ
σ
σ
τ
+
−
⎛
⎞
=
=
+
⎜
⎟
⎝
⎠
•
The principal stresses are obtained at
A
and
B
.
max,min
2
tan 2
ave
xy
p
x
y
R
σ
σ
τ
θ
σ
σ
=
±
=
−
Mohr’s Circle for Plane Stress
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•
The three circles represent the
normal and shearing stresses for
rotation around each principal axis.
min
max
max
2
1
σ
σ
τ
−
=
•
Radius of the largest circle yields the
maximum shearing stress.
Mohr’s Circle for ThreeDimensional Analysis of Stress