LectureCh3Torsion - Ch Ch. 3 Torsion Aircraft Structures,...

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h 3 T i Ch. 3 Torsion ircraft Structures EAS 4200C Aircraft Structures, EAS 4200C 9/17/2010 Robert Love Organizational: Turn in Project Part 1 at Front of Class i k HW #2 it G A d University of Florida Flight Controls/Visualization Laboratory Pick up HW #2 as it Goes Around
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Examples of Importance of Torsional Analysis •P a s t –W r i ght Brothers (wing warping) • Recent Past – Active Aeroelastic Wing F-18 – Boeing Dreamliner – Helicopter Rotors – HALE Aircraft ind Turbine Blades – Wind Turbine Blades • Future? –A FR L J o i n e d W i n g Sensor Craft g – Active Wing Morphing/Flapping Wings – ??? University of Florida Flight Controls/Visualization Laboratory
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Why Do You Need to Know How to Design For Torsional Loads? • AIAA DBF 2003: Wings Torsional Rigidity is Too Low! University of Florida Flight Controls/Visualization Laboratory What could they potentially have done to fix this?
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When is Wing Torsional Strength Really Important? • Where on the wing are your torsional loads the most? • Trends: What happens to the required torsional rigidity as: – Airspeed decrease – AR decrease – Pitching Moment decrease – Aileron power decrease – Move from root to tip – Move cg of wing closer to ¼ chord • Practicality: how do you increase torsional rigidity by wing design? University of Florida Flight Controls/Visualization Laboratory
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More Complex Situations Torsional Strength Is Needed • Structural Tailoring w/Composites – Bend/Twist Coupling eroelastic Phenomena Aeroelastic Phenomena – Bending Flutter (induces torsion) – Torsional Flutter (rare) ttp://www.youtube.com/watch?v=8D7YCCLGu5Y http://www.youtube.com/watch?v 8D7YCCLGu5Y http://www.youtube.com/watch?v=ca4PgyBJAzM • Aeroservoelastic Phenomena – Flapping Wings imit Cycle Oscillations University of Florida Flight Controls/Visualization Laboratory Limit Cycle Oscillations
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Efficiency in Torsional Design • Where is the material most efficiently used? ed=High Stress Blue=Low Stress Red High Stress, Blue Low Stress • What would be the most efficient torsional member? Why? hy can’t we always use that type of member? University of Florida Flight Controls/Visualization Laboratory Why can t we always use that type of member?
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3.1 Saint Venant’s Principle: Static Equivalence • Stresses or strains at a point sufficiently far from two applied loads don’t differ significantly if the loads have the same resultant force and moment (loads are statically equivalent ) • Distance req. 3x size of region of load application •E x : valid beyond 3x height of three stringer panel from the University of Florida Flight Controls/Visualization Laboratory load application end
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3.2 Torsion of Uniform Bars
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This note was uploaded on 06/06/2011 for the course EAS 4200C taught by Professor Kim during the Fall '09 term at University of Florida.

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LectureCh3Torsion - Ch Ch. 3 Torsion Aircraft Structures,...

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