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Airship Structural Analysis

Airship Structural Analysis. Lin Liao Aeronautical Engineer, PhD Worldwide Aeros Corp., Montebello, CA. Overview. Introduction Analysis of airships Rigid body motion analysis Static bending moment Aerodynamic bending moment Envelope stress analysis

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Airship Structural Analysis

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  1. Airship Structural Analysis Lin Liao Aeronautical Engineer, PhD Worldwide Aeros Corp., Montebello, CA The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  2. Overview • Introduction • Analysis of airships • Rigid body motion analysis • Static bending moment • Aerodynamic bending moment • Envelope stress analysis • Stress analysis of empennage attachment • Cable_truss structures • Summary The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  3. Introduction • Non-rigid airships • Empirical experiences “Airship Design”, “Airship Technology” • Finite Element modeling NASTRAN,ABAQUS • Rigid airships • Bulkhead construction • No FEA model of rigid airships The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  4. Vertical & Longitudinal Directions The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  5. Lateral Direction The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  6. Vertical & Longitudinal Directions • Calculation of lift, drag, and pitching moment • Sum of forces and moments in vertical & longitudinal directions The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  7. Lateral Direction • Sum of forces and moments in lateral direction The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  8. Flight Maneuver Conditions The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  9. Calculation of Static Bending Moment • The envelope is divided into longitudinal segments. • Distribution of buoyancy force is obtained by multiplying the segment volume by the Helium (96% purity as specified by ADC) unit lift. The buoyancy forces is given the (+) sign. • The segment envelope weight is obtained in proportion to the segment surface area, and given the (-) sign to denote weight downward. • The components (nose cone, helium, etc.) are placed in their nearest segment, and given the (-) sign. • The segment load F is obtained by summing up the above forces and weights. • The envelope shear at each segment, S, is obtained by summing the above F from the nose up to the segment where shear is determined. • The envelope bending moment at each segment, M, is obtained by summing the above S multiplied by the segment length, from the nose up to the segment where bending moment is determined. The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  10. Static Bending Moment Case 1 Envelope: 30% Car: 55% Case 2 Envelope: 36% Car: 50% The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  11. Static Bending Moment Case 3 Envelope: 37% Car: 48% • Static bending moment increases from zero to maximum along the longitudinal length of airships and then decreases to negative maximum. Maximum static bending moment decreases with the increase of envelope weight. The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  12. Aerodynamic Bending Moment Gust 1, Gust 2, and Gust 3: 20 ft/s, 25 ft/s, 30 ft/s The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  13. Aerodynamic Bending Moment The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  14. Envelope Stress Analysis • Envelope stresses due to internal pressure & bending moment • Pressurized airships and rigid airships The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  15. Stress Analysis of Empennage Attachment The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  16. Stress Analysis of Empennage Attachment The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  17. Cable_truss Structures • Restraints: fixed Nodes1, 4, and 5 • Applied loads: • Fx =1000 lbs at Nodes 9, 10, 11, 12 • Cable pretension: 100 lbs Cable tension in the deformed configuration The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  18. Cable_truss Structures • Restraints: fixed Nodes1-5, 9-13 • Applied loads: Fz =400 lbs at Nodes 7, 8, 15, 16 • Cable pretension: 100lbs • Three Design Configurations: • Design A: no cables are used • Design B: six cables are included • Design C: 14 cables (Each of four truss members is replaced by two cables) The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  19. Cable_truss Structures Displacements in the deformed configuration The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  20. Cable_truss Structures Displacements in the deformed configuration The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  21. Summary • Rigid body motion analysis has been utilized to study a variety of flight maneuver conditions of airships. • Static bending moment and aerodynamic bending moment are calculated. Aerodynamic bending moment increases with the increase of airship length and increases with the decrease of equivalent max diameter for the same volume and prismatic coefficients. Airship envelope stress is expressed as a function of bending moment and internal pressure. • Finite element model of empennage attachment of airships is presented. • Cable tension changes significantly in contrast with pretension and cables could completely lose tension. Optimal cable pretension and configuration are helpful for the minimization of structural deformation. The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

  22. Thank You! Questions? Suggestions? The Eighth Annual AIAA Southern California Aerospace Systems and Technology (ASAT) Conference Santa Ana, CA, May 21, 2011

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