ch01-03 stress & strain & properties

01 Solutions 46060 5/6/10 2:43 PM Page 50
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•1–73. Member B is subjected to a compressive force of
3
800 lb. If A and B are both made of wood and are thick,
1
determine to the nearest
4 in. 8 in.
the smallest dimension h of
the horizontal segment so that it does not fail in shear. The
average shear stress for the segment is t allow = 300 psi.
B 800 lb
t allow = 300 = 307.7
( 3 2 ) h
h = 2.74 in.
A
h
13
12
5
Use h = 2 3 4 in.
Ans.
1–74. The lever is attached to the shaft A using a key that
has a width d and length of 25 mm. If the shaft is fixed and
a vertical force of 200 N is applied perpendicular to the
handle, determine the dimension d if the allowable shear
stress for the key is t allow = 35 MPa.
a
A
d
a
20 mm
500 mm
a + ©M A = 0; F a - a (20) - 200(500) = 0
200 N
F a - a = 5000 N
t allow = F a - a
A a - a
; 35(10 6 ) =
5000
d(0.025)
d = 0.00571 m = 5.71 mm
Ans.
1–75. The joint is fastened together using two bolts.
Determine the required diameter of the bolts if the failure
shear stress for the bolts is t fail = 350 MPa. Use a factor of
safety for shear of F.S. = 2.5.
30 mm
80 kN
30 mm
350(10 6 )
2.5
= 140(10 5 )
t allow = 140(10 6 ) = 20(103 )
p
4 d2
d = 0.0135 m = 13.5 mm
40 kN
40 kN
Ans.
50