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Airframe structural Design for jntu students aeronautical
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Structures Responsibilities
a. Determine V-n relationships and establish a V-n diagram
b. Establish and maintain load paths
c. Determine component materials (weights and dimensions to configuration) and consider environmental impact of acquisition, production and operations
d. Determine landing gear configuration
e. Carry out a detailed structural design of the wing box and wing attachment and structurally design landing gear (weights & dimensions to configuration)
f. Employ FEM Analysis
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V-n Diagram
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/MainFrame?OpenFrameSet
Load Paths
• How loads are transferred from one structural member to another
• Wing skin—torsion and shear stress
• Wing ribs—maintain shape and rigidity, transfer loads from skin to spars
• Wing spars—bending moments
• Fuselage—bulkheads, framers, stringers
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Major Fuselage Loads
• Empennage loads due to trim, maneuvering, turbulence and gusts
• Pressure loads due to cabin pressurization
• Landing gear loads due to landing impact, taxiing and ground maneuvering
• Loads induced by the propulsion installation when the latter is attached to the fuselage
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Structural Components
• Spars• Ribs• Skin• Beam shear• Beam bending• Torsion
Cessna Citation II
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Materials
• Selection criteria– Strength– Stiffness– Density– Cost
• Typical materials– Aluminum– Composites – Steel– Titanium
• Mini-UAV materials– Plastic
– Balsa
– Fiber (cloth)
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Landing Gear Loads• Vertical loads primarily caused by non-zero
touchdown rates and taxiing over rough surfaces
• Longitudinal loads primarily caused by braking loads and rolling friction loads
• Lateral loads primarily caused by ‘crabbed landings,’ cross-wind taxiing and ground turning
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Structural Configuration (441 level)
I-beam gives good resistance to shear (web) and bending (caps)
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