Failure Mode And Energy Absorbing Of Metallic Rectangular Tubes Subjected To Axial Compression

Thin-walled metallic square and rectangular tubes have stable plastic deformation modes and excellent energy absorbing capability subjected to axial loading, which are utilized to make energy absorbing device generally.In this dissertation, the main buckling modes of square and rectangular tubes subjected to axial compression are introduced and some researches at home and abroad are summarized. A large number of simulations were finished with the help of FEA code ABAQUS, the results agree well with those obtained from theoretical models and test data.Dynamic behavior of square tubes and the influence to the collapse modes and energy absorbing capability of square tubes, including impact velocity, impact mass and transverse inertia, are carefully studied. The results show that the deformation modes of such structures are both velocity and mass dependent, square tubes reveal dynamic progressive buckling in low velocity impact and dynamic plastic buckling in high velocity impact. With the same impact energy, crushing distance is inversely proportional to the impact velocity and a larger proportion of the impact energy is absorbed at a given crushing distance during the entire response of the tube for the higher impact velocities.The analysis of geometrically equivalent cylindrical tubes under the same loading conditions manifests that the energy absorbing efficiency of cylindrical tubes is better than square tubes wherever in quasi-static compression or dynamic impact. The peak load and mean load of cylindrical tubes are higher than those of square tubes, but the main characteristics of the force-displacement histories have similar fluctuations.Small random geometrical imperfections with Poisson distributions are introduced in the simulations of rectangular tubes under axial impact with low velocity. The results show that the peak load decreases and the collapse distance increases with the introduction of initial geometric imperfections, but this variety is very little and it does not influence the initial or ultimate deformation modes. Moreover, the influences of material property, section properties, tube length and thickness to ultimate deformation modes are studied respectively.Under the same loading conditions and equivalent geometrical size, the energy absorbing efficiency of cylindrical tubes is better than that of square tubes, while the...