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Rectangular wing: chord = 0.5 m, span = 4 m, TOGW = 5,000 N, n max = 4 Wing area = 2 sq m, AR = b/c =8 Calculate total lift force (approx. normal force) on each wing: =15,000 N (Ultimate load on each wing) Distribute L w along wing span using strips of equal width Use 3 strips for this example problem Chord for elliptical wing Example - SF, BM, Torsion Calculation ) 2 / 5 . 1 * * ( n W L w = AE/ME350 Jha Loads-13 y-station Wing chord, c Elliptical c(y) Average chord 0 0.5 0.637 0.569 0.66 0.5 0.601 0.550 1.33 0.5 0.475 0.488 2 0.5 0 0.250 2 2 2 4 2 4(2) 2 ( ) 1 1 0.637 1 (4) 4 2 S y y y c y b b π = - = - = -

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Distribute lift force on each strip using Schrenk’s approximation Calculate strip area = (Average of geometric and elliptical chord)*width = Average chord*0.667 Calculate “factor” for lift distribution: L w = (factor)*(sum of strip areas) 15,000 N = (factor)*(0.965 sq m) factor = 15,544 N/sq m
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Unformatted text preview: AE/ME350 Jha Loads-14 Example - SF, BM, Torsion Calculation Strip Strip area Lift on each strip 1 0.373 5798 N 2 0.346 5378 N 3 0.246 3824 N Estimate shear force and bending moment SF at any y-station = sum of lift force outboard of y-station BM at any y-station = sum of (lift force * distance) outboard of y-station For calculating distance, assume lift acting through the center of strip width Calculate torque about 15% c using wing center of pressure at 25% c (good approximation at subsonic speeds); sum torque values from tip to root AE/ME350 Jha Loads-15 Example - SF, BM, Torsion Calculation y-station Shear Force, N Bending Moment, N-m 0 15000 13676 (6361+5381+1934) 0.667 9202 5620 (3826+1794) 1.33 3824 1275 2 0 0 Strip Torque, N-m 1 750 (460.1+289) 2 460.1 (191.2+268.9) 3 191.2...
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