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Aeroelasticity in Femap and NX Nastran
- 1. 5/22/2012 Page 1 Introduction to Aeroelastic Analysis Using NX NASTRAN with FEMAP Ben Names Email: Website: Phone: ben@structures.aero http://structures.aero/ Phone: (703) 935-2827 Today’s topics: • Static Aeroelasticity • Aeroelastic Tailoring • Flutter
- 2. 5/22/2012 Page 2Page 2 Presentation Summary • SDA Overview • Aeroelasticity Overview • Static Aeroelastic Example • Aeroelastic Tailoring • Flutter Example • Conclusions
- 3. 5/22/2012 Page 3 NASTRAN Capabilities • SOL 144 – Static Aeroelastic Response • SOL 145 – Aerodynamic Flutter • SOL 146 – Dynamic Aeroelastic Response • SOL 200 – Sensitivity and Optimization • Aerodynamic Theories – Doublet Lattice Method (subsonic compressible) – ZONA51 (supersonic) – Mach Box (Supersonic) – Strip Theory (Any) – Piston Theory (Hypersonic) • Most aerodynamic theories are based in potential flow – No viscous terms = NO DRAG! • For more info on the Doublet Lattice Method, check out the NASTRAN documentation or my thesis: – http://www.slideshare.net/BenNames/namesbjt2016-65943918?ref=https://www.linkedin.com/
- 4. 5/22/2012 Page 4 Aeroelasticity • Coupling between aerodynamic forces, inertial forces, and elastic forces: Dynamics (Inertial Forces) Dynamic Aeroelasticity (Flutter and more) Static Aeroela sticity Flight Mechanics Fluid Mechanics (Aerodynamic Forces) Structural Mechanics (Elastic Forces) Structural Dynamics SCAC L U U SCAC L U SC AC L
- 5. 5/22/2012 Page 5 Static Aeroelastic Demo! • Problem: You are a part of a team that is testing a wing in a wind tunnel and your job is to predict whether it will break! • Cantilevered, composite wing in a wind tunnel (x-z aero symmetry) • Span of 160 in • Chord of 17 in • U = 74 mph (1300 in/s) • Sea level density = 0.0023769 slug/ft^3 (1.146e-7 slinch/in^3) • q = 0.968 psi • 1 degree AoA View the Demonstration
- 6. 5/22/2012 Page 6 Aeroelastic Tailoring • Use anisotropic material behavior to manipulate wing loading • Add stiffness couplings to the wing • bending-torsion • shear-torsion • This tailoring can result in various behaviors, including reducing the root bending moment of a wing
- 7. 5/22/2012 Page 7 Aeroelastic Tailoring in Action! • Blue laminate will be soft, fiberglass skin • By choosing specific layup schedules in laminates 1, 2, 3, and 4, we can achieve bending-torsion coupling in our new composite wing box • 𝜃 values of -20, -10, 0, 10, and 20 will be sampled. 1 3 2 4 Laminate Number Layup Schedule 1 𝜃° 8 2 ±45° 2 3 −𝜃° 8 4 ∓45° 2 Design
- 8. 5/22/2012 Page 8 Spanwise Loading of the Wing Rigid Increasing theta, the angle of spar cap plies Min, θ=-10° Max, θ=20°
- 9. 5/22/2012 Page 9 Internal Shear Force Increasing theta, the angle of spar cap plies Min, θ=-10° Max, θ=20° Rigid
- 10. 5/22/2012 Page 10 Internal Bending Moment Increasing theta, the angle of spar cap plies Min, θ=-10° Max, θ=20° Rigid
- 11. 5/22/2012 Page 12 Flutter • Flutter is a coupling between the inertial, aerodynamic, and elastic forces • Much harder to predict than the quasi-static behavior since it is a coupling between 3 sets of forces, not two • Can predict both dynamic as well as static instability (i.e., flutter and divergence) View the Demonstration
- 14. 5/22/2012 Page 16 V-g Detailed View Flutter Speed 1: V=123 mph Flutter Speed 2: V=228 mph With a small amount of structural damping (1-5%), it is likely that mode 4 would go unstable before mode 2
- 15. 5/22/2012 Page 17 About SDA (aka “Structures.Aero”) • SDA was founded in 1997 and provides expert aerospace structural analysis • We serve a variety of industries • We specialize in composites, and developing strong, lightweight structures that are readily manufacturable • Low level support up through developing test plans and advanced stress analysis • Typical support programs include small to large UAVs, manned and unmanned spacecraft, naval structures • Our team consists of over a dozen B.S., M.S., and PhD level engineers • SDA is located in Sterling, VA, just north of Dulles Airport near Washington DC
- 16. 5/22/2012 Page 18Page 18 Typical Projects we support • Some of our previous projects include: – Aircraft • Aurora Excalibur • MHADD ARES • Vanilla VA1 • Lockheed Constellation restoration for Lufthansa – Spacecraft • NASA NESC Composite Crew Module (CCM) • NASA NESC Max Launch Abort System (MLAS) • NASA James Webb Space Telescope/IEC • NASA Orion Heatshield mass reduction for NESC • NASA Orion Crew Module (with Lockheed) • NASA WFIRST Telescope for Goddard Aerosonde Heatshield Shadow M2 CCM Orion Crew Module
- 17. 5/22/2012 Page 19Page 19 Partnerships Siemens Value Added Reseller Collier Research Corporation Reseller FEMAP NX Nastran Fibersim Solid Edge HyperSizer Pro HyperSizer Express
- 18. 5/22/2012 Page 20Page 20 Additional Resource What The only Siemens-approved third part resource book for new users of Femap. Published Fall 2014 Why Learning with the help documentation can be like drinking from a fire hose. Learning Femap succinctly covers the bases on using Femap without being a “bible”. Covers Introduction Femap Application Interface Modeling/ Pre-Processing Analysis Post-Processing Programming Femap How Explanation of features Numerous illustrations Annotated examples Guided tutorials Learning Femap ISBN 978-1-4951-2963-6 By Eric Gustafson (eric@structures.aero), Senior Aerospace Stress Analyst, SDA $49.99 *B&W, color available Available online at www.learningfea.com
- 19. 5/22/2012 Page 21Page 21 Contact Us: Contact: Marty Sivic Email: msivic@structures.aero Website: http://structures.aero/ Phone: (724) 382-5290 Try FEMAP For Free! Download a free 45-day trial of FEMAP with NX Nastran • Full FEMAP capabilities • All Nastran solution sequences included • (http://structures.aero/femap-trial/) Contact: Ben Names Email: ben@structures.aero Website: http://structures.aero/ Phone: (703) 935-2827