Mechanics of materials test(1)
四技自控 二乙
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1. Knowing that P = 9 kN and the system is in equilibrium.
(a) The average normal stress in the middle point of bar AB is  AB =
(b) The smallest allowable diameter of the pin at B (i.e. dB =
the pin is not exceed 120 MPa.
(c) The corresponding average bearing stress  bAB =
(d) The corresponding average bearing stress  bB =
MPa.
mm) if the average shearing stresses in
MPa in member AB at B.
MPa in each of the support brackets at B.
(e) If the diameter of cord AC is 10 mm, determine the normal stress  AC =
MPa in the cord.
12 mm
16 mm
12 mm
P
75
0m
m
A
50 mm
40
B
C
750 mm
2. A 1/2 in. diameter steel rod AB is fitted to a round hole near end C of the wooden member CD. For the
loading shown, determine
(a) the maximum average normal stress  =
psi in the wood
(b) the distance b =
in. for which the average shearing stress is 90 psi on the surface indicated by
the dashed line.
(c) the average bearing stress  b =
psi on the wood.
1000 lb
3/4 in
500 lb
D
A
3 in
500 lb
B
C
b
3. Two solid cylindrical rods AB and BC are welded together at B and located as shown.
(a) Knowing that the diameter of rods AB and BC are d AB  1.25 in and d BC  0.75 in , respectively.
The average normal stress in the section AB is  AB =
 BC =
psi and in the section BC is
psi.
(b) Knowing that the normal stress must not exceed 25 ksi in either rod, determine the smallest allowable
in. and d BC =
values of the diameter d AB =
in.
30 in
A
12 kips
25 in
B
C
10 kips
4. The two portions of member AB are glued together along a plane forming an angle  with the horizontal and
subjected to maximum applied force P = 10 kN.
(a) Knowing that   30  , determine the normal stress   =
 =
MPa and shear stresses
MPa in the glued splice.
(b) If the ultimate stress for the glued joint is 20 MPa, determined the factor of safety n =
in the
design.
(c) Knowing that the ultimate stress for the glued joint is 17 Mpa in tension and 9 Mpa in shear, determine the
range of values of  (i.e.
least 3.0.
 
) for which the factor of safety of the member is at
P
A
section
30 mm

B
50 mm
5. The bar is supported by the pin. If the allowable tensile stress for the bar is ( t ) allow  21 ksi , and the
allowable shear stress for the pin is  allow  12 ksi . Assume the hole in the bar has the same diameter as the
pin. Take t = 1/4 in. and w = 2 in.
(a) Determine the diameter d =
(b) What is the maximum load P =
(c) the corresponding bearing stress  b =
in. of the pin for which the load P will be a maximum.
lb and
psi on the bar.