23

MECHANICS OF MATERIALS PROBLEMS CURTISS-WRIGHT ENGINEERING
Course B-4 Seely: Arts. 38-39;41 CADETTES 15D-A-122

15D-1 Fig. 15D-1 shows the cross-section of a wing spar. Determine the
unit shearing stress one inch from the top of the beam if the external
shear is 200 lb.

15D-2. A hollow steel tube is used as a beam 8 ft. long. It is simply
supported at points 2 ft. from each end and carries a downward
load of 2,000 lb. at each end. It also carries a uniform load
of 500 lb./ft. between the supports. The OD is 2 in. and the
thickness is 1/4 in. Determine the maximum vertical shearing
unit stress in the beam.

15D-3. The cross-section of a solid spruce spar is shown in Fig. 15D-3.
The spar is 14 ft. long and is cantilevered to the fuselage of
the airplane. The modulus of rupture for spruce may be taken as
8,000 p.s.i.
(a) Determine the maximum uniformly distributed load which can be
applied to the wing spar with a load factor of 4 if the modulus
of rupture governs the design.
(b) Determine the maximwn longitudinal unit shearing stress in
the wing spar due to the design load obtained in part (a).

[images]
Fig. 15D-1

Fig. 15D-3