Nonlinear Finite Element and Post-Buckling of Large Diameter Thin Walled Tubes

Abstract

This study investigates the crush behaviour of a relatively large diameter, thin walled tube through both experimental and finite element methods. The experiments were conducted using test specimens of cylindrical tube which were placed into a load press, and crushed by a distance of 150 mm. The thin walled tubes were found to collapse through localised buckling, with a folding layered mode of failure. Numerical analysis of the cylindrical tube was conducted using finite element (FE) methods through an explicit analysis (utilising a three dimensional shell model). Through the use of both ductile damage criteria and the Müschenborn–Sonne forming limit diagram (MSFLD), the model was able to initiate buckling failure without creating imperfections. The numerical model exhibited a similar layered, ring-folding mode of failure as observed in the experiment. Shear failure was also analysed, however caused a large amount of element distortion. The model showed a large degree of sensitivity to the coefficient of friction used in contact between the tube and the press. With the careful selection of mesh density, friction coefficient, and material properties, the FE model demonstrated very good correlation with the experiment in terms of critical buckling force and post-buckling response.