Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

614 CHAPTER 22 Wings

Ans. σ 1 =−190.7N/mm^2 σ 2 =−181.7N/mm^2 σ 3 =−172.8N/mm^2

σ 4 =−163.8N/mm^2 σ 5 =140N/mm^2 σ 6 =164.8N/mm^2

σ 7 =189.6N/mm^2 σ 8 =214.4N/mm^2.

P.22.2 Figure P.22.2 shows the cross section of a two-cell torque box. If the shear stress in any wall must not
exceed140N/mm^2 ,findthemaximumtorquewhichcanbeappliedtothebox.
Ifthistorquewereappliedatoneendandresistedattheotherendofsuchaboxofspan2500mm,findthetwist
indegreesofoneendrelativetotheotherandthetorsionalrigidityofthebox.TheshearmodulusG=26600N/mm^2
forallwalls.Dataareasfollows:

Shadedareas: A 34 =6450mm^2 ,A 16 =7750mm^2

Walllengths: s 34 =250mm,s 16 =300mm

Wallthickness: t 12 =1.63mm,t 34 =0.56mm

t 23 =t 45 =t 56 =0.92mm

t 61 =2.03mm

t 25 =2.54mm

Ans. T=102417Nm,θ=1.46◦,GJ= 10 × 1012 Nmm^2 /rad.

Fig. P.22.2

P.22.3 Determinethetorsionalstiffnessofthefour-cellwingsectionshowninFig.P.22.3.Dataareasfollows:

Wall 12 23 34
78 67 56 45◦ 45 i 36 27 18
Peripherallength(mm) 762 812 812 1525 356 406 356 254
Thickness(mm) 0.915 0.915 0.915 0.711 1.220 1.625 1.220 0.915

Cellareas(mm^2 ) AI= 161500 AII= 291000
AIII= 291000 AIV= 226000
Ans. 522.5× 106 GNmm^2 /rad.