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T P j tTerm Project
Design & Analysis of a Minimum Weight Wing
AE 462 Aerospace Structures DesignAE 462 Aerospace Structures DesignDepartment of Aerospace Engineering, METU
Odeh Dababneh, 132180‐1Coşkun ÖZAŞÇILAR 102876‐0Coşkun ÖZAŞÇILAR, 102876 0
18 June 2009
Project Definition
The properties of the designp p g
Half wing structure for a single engine utility aircraft
Straight and unswept wing = RectangularStraight and unswept wing = Rectangular
NACA 2412 Wing
Chord : 1.524 m (5 ft)
Semi span: 4.572 m (15 ft)
Aircraft Maximum Takeoff Weight: 1460 kg
Aircraft Minimum Operating Weight: 861 kg
Dive Speed: 270 mile per hour
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 2
Design Requirements
Minimum weight designMinimum weight design
FAR Part 23 Appendix AFAR Part 23 Appendix A
f b l & d dManufacturability & standard size
Factor of Safety = 1.5
Divergence Speed > Dive Speed
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 3
Loading @ A
3000035000
Spanwise Shear Force Distribution
50001000015000200002500030000
Spanwise Bending Moment Distribution0
5000
0 0.2 0.4 0.6 0.8 1 1.2Unit Span (m)
40000500006000070000
Spanwise Bending Moment Distribution
Spanwise Pitching Moment Distribution(N.m)0
100002000030000
0 0 2 0 4 0 6 0 8 1 1 2
-800-600-400-200
00 0.2 0.4 0.6 0.8 1 1.2
p g ( ) 0 0.2 0.4 0.6 0.8 1 1.2Unit Span (m)
-1600-1400-1200-1000
Unit Span (m)
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 4
Loading @ D
250003000035000
Spanwise Shear Flow Distribution
500010000150002000025000
VZ (N
)
6000070000
Spanwise Bending Moment Distribution
00.000 0.200 0.400 0.600 0.800 1.000 1.200
Unit Span (m)
2000030000400005000060000
S i Pit hi M t
01000020000
0.000 0.200 0.400 0.600 0.800 1.000 1.200Unit Span (m)
-2000
-1000
00.000 0.200 0.400 0.600 0.800 1.000 1.200
Spanwise Pitching Moment
-5000
-4000
-3000
Unit Span (m)
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 5
Unit Span (m)
Selection of Analysis Tool
Analysis tool = MATLAB 2006aAnalysis tool = MATLAB 2006a
The tool must be well known by all the project partners.
The tool must be capable of mathematical operations.
The tool must be capable of programming through an algorithm.p p g g g g
The tool must be capable of presenting charts and graphs.
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 6
The Flowchart ‐ I
STARTB
Input: General wing geometry, flight parameters, factor of safety
C l l t E t l L d (ESDU)
Calculate: Inertial and geometrical parameters
Calculate: External Load (ESDU)
Calculate: Internal Load
Calculate: Axial stress and Shear FlowsRe‐Sizing
Check: Axial
C
Initial sizing (geometry and material)
Check: Axial Strength and Shear Stress
FAILED
Calculate: Critical buckling stressesFAILED
Assume: Shear center = aerodynamic center
FAILEDA
Check: Buckling Condition
OKA Condition
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 7
The Flowchart ‐ II
A
Calculate: Margin of Safety (MoS)Calculate: Divergence speed
Calculate: Margin of Safety (MoS)
Check: Minimum positive
MoS
>> 0+
Comparing weights for points A & D, decide the most critical divergence
speed: at A or D?:
≈ 0+
Calculate: Shear Center @ each section
FINISHB
Check:Shear Center Location
Δ > 1%
Carry the loads to shear centers
Calculate: Minimum Weight
Δ < 1%
CCalculate: Sectional GJ and S/C‐A/C
distance at 75% wing span
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 8
Selection of Material
Aluminum 2024‐T3
• High strength Aluminum and excellent fatigue resistance.
• Advantage on structures and parts where good strength‐to‐weight ratio is desired.
MATERIAL PROPERTIES
Ulti t T il St th 483 MPUltimate Tensile Strength 483 MPa
Tensile Yield Strength 345 MPa
Modulus of Elasticity 73,1 GPay
Shear Modulus 28 GPa
Shear Strength 283 MPa
Density 2780 kg/m3
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 9
Spar Caps and Stiffners: Location & Areas
X3X2
X1
X4
Unsymmetric Bending Formula Best Location for Minimum Spar & Stiffner Area
12 % ≤ X1 ≤ 20 % of Chord X1 = 20
55 % ≤ X2 ≤ 70 % of Chord X2 = 55
X1 X2
X3 X4
X1 ≤ X3 ≤ X2 X3 = 32
X1 ≤ X4 ≤ X2 X4 = 31Iterate the locations, keep all else constant...
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 10
Skin, Web & Rib Thicknesses
Skin 1Skin 2
Spar Web 1 Spar Web 2
Skin 3
Shear Flows Max Shear Stress Minimum Thickness Check Buckling Minimum Thickness
Skin Thicknesses
Web Thicknesses
All Thicknesses
For Buckling
Iterate the thicknesses, keep all else constant...
Rib thicknesses are determined here...
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 11
Margin Of Safety
FLANGES
Root
Tip
WEB & SKINS
Root
Tip
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 12
Shear Center
Manual iteration for the shear center location:
Shear Center = Aerodynamic Center = 25 % chord
Shear Center = 42 % chordRe‐calculate all
Assume
Shear Center 42 % chord
Shear Center = 44 % chord
Re calculate all
Re‐calculate all
Shear Center = 44 % chordRe‐calculate all
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 13
Note on Weight Optimization
Component PercentageComponent Percentage
Skins 60%
Spar Caps & Stiffners 20 %
Spar Webs 10 %
Ribs 10 %
TOTAL 100 %
Weight reduction on SKINS is more effective
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 14
Manufacturability & Standards
Aluminum 2024 T3
48" x 144" 0.012" 0.016" 0.020" 0.025" 0.032" 0.040" 0.050"
1219mm x 144mm 0.30mm 0.4mm 0.5mm 0.63mm 0.81mm 1.016mm 1.27mm
48" x 144" 0.063" 0.071" 0.080" 0.090" 0.100" 0.125" 0.160"
1219mm x 144mm 1.60mm 1.8mm 2.03mm 2.28mm 2.54mm 3.17mm 4.06mm
Al 2024 T3 Angles (L – Profile)
Dimensions (inch) Areas (mm^2)
1/2 X 1/2 X 1/16 38
5/8 X 5/8 X 1/16 48
3/4 X 3/4 X 1/16 58
7/8 X 7/8 X 1/8 131
1 X 1 X 1/16 78
1 X 1 X 1/8 151
1 X 1‐1/2 X 1/8 232
1‐1/2 X 1‐1/2X1/16 118
1‐1/2 X 1‐1/2X1/8 232
2 X 2 X 1/8 312
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 15
3‐1/2 X 3‐1/2X1/4 1.089
Result: Cross Sections, Spacings & Thicknesses
AREAS (mm^2)
Spar Cap 1 Spar Cap 2 Spar Cap 3 Spar Cap 4 Stiffner 1 Stiffner 2
ROOT 520 360 315 375 520 400
TIP 38 38 38 38 38 38
ROOT TIP
Station 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Percent 0 3 6 9 13 17 22 27 34 41 48 55 65 85 100
Y (m) 0 0.046 0.091 0.137 0.198 0.259 0.335 0.411 0.518 0.624 0.731 0.838 0.991 1.295 1.524
THICKNESS(mm)
Skin 1 Skin 2 Skin 3 Spar Web 1 Spar Web 2 Rib 1 Rib 2
ROOT 1.6 1.6 2.03 1.6 1.6 1.2 1.6
TIP 0.63 0.81 0.81 0.63 0.63 0.3 0.3
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 16
Result: Weight
C tA D
Componentkg % kg %
Skins 29.267 56.5 30.708 57.7
Spar Caps & Stiffners 10.998 21.2 11.023 20.7
Spar Webs 4.924 9.5 4.818 9.1
Ribs 6.595 12.8 6.656 12.5
TOTAL 51.784 100 53.205 100
Divergense Speed@ A
308 6 /
Divergense Speed@ D
322 8 /308.6 m/s 322.8 m/s
Department of Aerosace EngineeringMiddle East Technical Universityby Odeh Dababneh & Coşkun Özaşçılar
19.06.2009AE 462 Term Project: Design & Analysis of a Minimum Weight Wing
Page 17