Page 401 - Aircraft Stuctures for Engineering Student

382 Stress analysis of aircraft components

Fig. 10.16 Idealized section of a multicell wing.

Example 10.6
The wing section shown in Fig. 10.17 has been idealized such that the booms carry all
the direct stresses. If the wing section is subjected to a bending moment of 300 kNm
applied in a vertical plane, calculate the direct stresses in the booms.

Boom areas: B1 = B6 = 2580mm2, B2 = B5 = 3880mm2, B3 = B4 = 3230mm2

We note that the distribution of the boom areas is symmetrical about the horizontal
x axis. Hence, in Eq. (9.6), Ixy = 0. Further, Mx = 300kNm and My = 0 so that
Eq. (9.6) reduces to

MXY
a, = -
IXX
in which

IxX = 2(2580 x 1652 + 3880 x 2302 + 3230 x 2002) = 809 x 106mm4

Hence

The solution is now completed in Table 10.4 in which positive direct stresses are
tensile and negative direct stresses compressive.

Fig. 10.17 Wing section of Example 10.6.