7 crippling example given 8 inch long column with

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7 Crippling Example • Given: – 8 inch long column with cross section shown – E = 10,000 ksi, yield strength = 70ksi, I z = 0.00055 in 4 = min I Find Primary and Secondary buckling loads Find length where primary = secondary buckling 37 Other Buckling Considerations Post buckling strength – average of crippling strength of individual flanges M t b kli l t Master buckling plot Elastic column Tangent modulus column (inelastic) Secondary buckling (local crippling) Johnson-Euler curve 38 Master Buckling Curve Show buckling failure stress F c for primary (Euler), inelastic inelastic (Engesser) and secondary (crippling) failure versus slenderness ration kL/r = L’/ ρ 39 Ref: M. Niu, Airframe Structural Design , CONMILIT Press, Ltd, 1988, Ch 5. Master Buckling Curve for Primary, Inelastic, and Crippling failure Stress F c Ref: M. Niu, Airframe Structural Design , CONMILIT Press, Ltd, 1988, Ch 5. 40 Stiffened Panel Buckling Flexural instability (Euler - primary) Local instability Several Buckling modes for stiffened panels Torsional instability Inter-rivet buckling • Wrinkling Stiffened Panel “Collapse” Failure depends on combination of buckling modes If near primary mode – any of secondary modes will lead to complete collapse If well below primary buckling mode (“short panel) – skin can buckle without complete failure (stringer carries load) – other secondary modes come into play “Ideal” solution (most efficient use of material) when secondary modes lead to failure at same time.
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AAE 454 - Spring 2013 ©2013 A. F. Grandt, Jr. 8 Stiffened Panel Buckling Flexural instability (Euler - primary) Local instability Several Buckling modes for stiffened panels Torsional instability Inter-rivet buckling • Wrinkling Stiffened Panel “Collapse” Failure depends on combination of buckling modes If near primary mode – any of secondary modes will lead to complete collapse If well below primary buckling mode (“short panel) – skin can buckle without complete failure (stringer carries load) – other secondary modes come into play “Ideal” solution (most efficient use of material) when secondary modes lead to failure at same time.
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  • Winter '14
  • Shear Stress, Yield surface, Buckling, Euler Column Buckling, A. F. Grandt

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