Quasi-Static and Dynamic Axial Crushing of Various Polygonal Tubes

Various polygonal tubes were compressed in the axial direction under quasi-static and dynamic loading conditions. The effect of the polygonal shape and the wall thickness on the crush behavior is investigated, in which the cyclic buckling takes place. The numbers of polygonal edges were 3, 4, 5, 6 and 7 in the experiment. A circular tube was also tested for comparison. The tubes were machined from aluminum alloy A5056 bar. Crush strength is estimated as an index of the energy absorption capacity of the tube. It increases with increasing the number of polygonal edges of the tube, although it almost saturates when the number of polygonal edges is more than 6. For the wider variety of polygonal tubes than that in the experiment, numerical simulation is performed using the dynamic explicit finite element code DYNA3D. The computed crush behavior well agrees with the corresponding experimental one, however, the difference in collapse mode arises due to the slight imperfections in experiment. The deformation pattern becomes more irregular for the thinner-walled tube. Further, it is presumed that the large hardening exponent in the plastic property of the material could prevent the buckling switching from the symmetric mode to asymmetric one in the crushing of circular tube.