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Lauren Kougias

A Study of the Effect of Imperfections on Buckling Capability in Thin Cylindrical Shells Under Axial Loading. Lauren Kougias. Objective. To study the effect of ovalization of a thin cylindrical shell on load carrying capability under an axial compressive load

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Lauren Kougias

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  1. A Study of the Effect of Imperfections on Buckling Capability in Thin Cylindrical Shells Under Axial Loading Lauren Kougias

  2. Objective • To study the effect of ovalization of a thin cylindrical shell on load carrying capability under an axial compressive load • Evaluate buckling capabilities for several values of e

  3. FEA Modeling and Part Dimensions • Thin cylindrical shell modeled using shell elements • AMS 4829 (Ti 6-4) properties used at 70°F • Cylinder Dimensions • R = 40” • L = 80” • t = 0.15”

  4. Buckling Capability: Theoretical Solution • Theoretical solution for perfect (e = 0”) cylinder: 1,455,952 lb • E = Young’s Modulus • v = Poisson’s Ratio • t = wall thickness • R = radius • Solution based on experimental data: 420,736 lb • kc = buckling coefficient

  5. Methodology • Used eigenvalue buckling solution to perform mesh density study to find appropriate element size for analysis for perfect cylinder (e = 0). • Eigenvalue buckling solution used to create imperfections in model for nonlinear buckling. • Nonlinear buckling analysis performed using Riks modified method for perfect cylinder (e = 0). • Riks method is a solution method in Abaqus that models postbuckling behavior of a structure. • Nonlinear buckling analysis performed for several ovalized cylinders (e = 0%-100% of shell thickness)

  6. Eigenvalue Buckling Solution • Eigenvalue buckling mode four best represents ovalized shape • Mesh density study resulted in element size of 2” to yield an accurate solution.

  7. Nonlinear Buckling Results, e = 50%

  8. Summary of Nonlinear Buckling Results Theoretical Solution

  9. Typical behavior of a structure undergoing collapse (on left). Behavior of structure with e = 50% closely matches predicated curve. Load vs. Displacement Curves

  10. Conclusion • Adding imperfections in the form of ovalization significantly reduced the load carrying capability of the structure. • Further studies that take other types of imperfections into account must be addressed • Only addresses isotropic materials and the results should not be assumed to be the same for a composite structure

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