Axial crush of hollow cylindrical structures with various polygonal cross-sections: Numerical simulation and experiment

The crush behaviors of hollow cylindrical structures with various regular polygonal cross-sections are numerically investigated under axial compression using the FEM program code of the public domain version of DYNA3D. The effects of wall thickness and plastic hardening rate of material on the crush behavior are also investigated. Crush strength increases as the number of corners of the cross-section increases, though it almost saturates for the number of corners beyond 11. Cross-sectional shape with less than six corners should be avoided to take a regulated collapse pattern. The effect of number of polygonal corners on enhancement in crush strength becomes more prominent as the initial wall thickness decreases. Higher plastic hardening rate stabilizes the collapse pattern, where it is a symmetric accordion mode in circular cross-section, otherwise asymmetric diamond one occurs. Further, for hollow cylindrical structures with circular or square cross-section which are aluminum alloy extrusions, quasi-static and impact axial compression tests and the corresponding computations are carried out. As for the circular cross-section, the number of corners induced during collapse increases as the initial wall thickness decreases both in the experiment and the numerical simulation. Crush strength is lower for square cross-section than that for circular one. This tendency agrees with the computational result.