102810
Name:
EAS4200C Aircraft Structures I
2
nd
INTERM EXAM
You may use only one 8.5x11” formula page and no calculators. Note that
you must give the
equations that you use (with letters) before you substitute numbers into them
. Please sign a
pledge that you have not violated any of the university honesty provisions with regards to this exam.
_____________________
1.
(40%) The cross section below is a square of size h with four stringer areas as
shown. It is acted on by a moment M
y
of absolute magnitude M that compresses the
top stringers and a moment M
z
of absolute magnitude 2M that compresses the left
stringers.
a.
Define the signs of the moments.
The equation for the stresses is
y
z
xx
y
z
M
M
z
y
I
I
. Since M
y
causes negative
stresses for positive z it is negative, and since M
z
causes negative stresses for
negative y’s it is positive.
b.
The centroid is at a distance h/3 from the right flange, and the moments of inertia
are I
y
=1.5Ah
2
, I
z
=(4/3)Ah
2
. Find the equation of the neutral axis and draw it on the
figure.
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 Fall '09
 Kim
 Materials Science, Force, Yield surface

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