AAE 352
Homework #7
Due: October 31, 2011
Problem 1
Cut a strip of paper four inches wide.
With a knife or scissors cut a center crack (slit) of
length 2
a
= 1.5 inches in the top half.
In the bottom half cut two edge cracks with
a
= 0.60
inches.
Based on calculations of stress intensity factors, predict where the paper strip will fail
if the strip is loaded in uniaxial tension.
Show your work.
Then, confirm your answers by
rolling the two ends of the paper around pencils and pulling until it fails.
Tape your broken
“test specimen” onto a sheet of paper and turn it in with your assignment.
Problem 2
Consider a part made from 7075T651 aluminum with properties: yield strength
σ
Y
=
505 MPa, ultimate strength
σ
u
= 570 MPa, and plane strain fracture toughness (in US
Customary units) is
K
Ic
= 26
in
ksi
. The part has dimensions of 10 mm thickness
and 100 mm total width as shown, and will be loaded by static tensile loads
P
as
shown.
a)
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 Fall '08
 Chen
 Tensile strength, Fracture mechanics, central crack

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