Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

19.2 Idealization of a Panel 539

Fig.19.3

Idealization of a panel.

Similarly,

B 2 =

tDb

6

(

2 +

σ 1

σ 2

)

(19.2)

InEqs.(19.1)and(19.2),theratioofσ 1 toσ 2 ,ifnotknown,mayfrequentlybeassumed.
ThedirectstressdistributioninFig.19.3(a)iscausedbyacombinationofaxialloadandbending
moment.Foraxialloadonlyσ 1 /σ 2 =1andB 1 =B 2 =tDb/2;forapurebendingmoment,σ 1 /σ 2 =− 1
andB 1 =B 2 =tDb/6.Thus,differentidealizationsofthesamestructurearerequiredfordifferentloading
conditions.

Example 19.1
Partofawingsectionisintheformofthetwo-cellboxshowninFig.19.4(a),inwhichtheverticalspars
are connected to the wing skin through angle sections, all having a cross-sectional area of 300mm^2.
Idealizethesectionintoanarrangementofdirectstress-carryingboomsandshear-stress-only-carrying
panelssuitableforresistingbendingmomentsinaverticalplane.Positiontheboomsatthespar/skin
junctions.

Fig.19.4

Idealization of a wing section.