Page 349 - Aircraft Stuctures for Engineering Student

330 Open and closed, thin-walled beams

-
1
2
v 3
1.5 mm 200 mm - - t
-
2mm -
5 4
6 6

Fig. 9.48 Idealization of a wing section.
plane the direct stress at any point in the actual wing section is directly proportional
to its distance from the horizontal axis of symmetry. Further, the distribution of
direct stress in all the panels will be linear so that either of Eqs (9.70) or (9.71) may
be used. We note that, in addition to contributions from adjacent panels, the boom
areas include the existing spar flanges. Hence

2.0 x 600 ( ;;l)
or
6
B1 = 300 + 3.0x400(2-l)+ 6 2+-
which gives

B1(= B6) = 1050mm2
Also

i.e.
)
M

)
+
B2 = 2 x 300 + 2.0 x 600 ( 2M) 2.5 x 300 (2-1)+ 1.5 x 600 ( K
2+-
2+-
6
6 6
from which
B2(= Bs) = 1791.7~
2
Finally
i.e. 1.5 x 600 (
B3 = 300 + k%) + 2.0 x 200
6 2+- (2 - 1)
so that
B3(= B4) = 891.7mm 2