Deformation And Energy Absorption Properties Of Thin-walled Metal Tubes Filled With Aluminum Foam Under Lateral Load

Thin-walled metal tube structure is one of the most common and most effective energy absorption component, and has been widely used in the collision energy buffer system of automobile, rail transit, airplane and steamship etc., almost all of the transportation, and highway guardrail, defense arms device. When a collision does occur, thin-walled metal tubes can dissipate or absorb impact energy in different plastic deformation modes. Typical porous materials, for example aluminum foam, has such advantages as small density, high specific energy absorption and strong shock resistance and so on. But due to its poor tensile, compressive, bending and torsion strength, the application of aluminum foam materials in engineering fields is limited certainly. The combination of the two into filling structure or sandwich structure would be an ideal and efficient energy absorption components. This paper mainly focused on aluminum foam-filled tubes, a systematic study on deformation modes, bearing capacity and energy absorption properties of empty tubes and foam-filled tubes under lateral quasi-static and dynamic load is carried out through theoretical, experimental and numerical methods. The specific work contents are summarized as followings:Assuming that the absorbed energy of aluminum foam-filled tubes under lateral quasi-static loading consist of the energy absorption dissipated by metal thin-walled tubes and aluminum foam cylinder, based on the energy method, some theoretical relations are derived to estimate the instantaneous and mean lateral force, as well as the energy absorption of aluminum foam-filled tubes during the flattening process. And then some lateral compression tests in quasi-static condition were carried out on the empty and foam-filled tubes. By comparing the experimental results with the theoretical prediction, it turned out to be a good agreements between them, so it verifies the rationality of the theoretical model. Additionally, the influences of geometrical dimensions of tubes and the density of aluminum foam on instantaneous, mean lateral force and energy absorption are discussed based on the established theoretical model. The results show that, the instantaneous and mean lateral force, as well as the energy absorption of aluminum foam-filled tubes under lateral quasi-static loading are all higher than that of metal thin-walled tubes. The total energy absorption and lateral force increases with the increasing of tube length, thickness and diameter. And when the density of aluminum increases, the total energy absorption and lateral force of foam-filled tubes increase, accordingly.The mechanical response of thin-walled metal tubes filled with aluminum foam under lateral impact loading is studied. The corresponding numerical simulation analysis was performed by using the finite element software LS-DYNA. Compared with the results of numerical simulation and experiment, a good correlation between them affirms the validity of the finite element model and the accuracy of the calculation results. On the basis, the influences of geometric parameters of tube, density of aluminum foam and impact velocity on deformation regularity and energy absorption properties were discussed systematically. The progressive collapse of foam-filled tubes under lateral impact loading can be divided into three phases: initial collision stage, platform stage and densification stage. When the impact velocity exceeds a certain value, the deformation mechanism of foam-filled tubes is changed; it transforms from symmetric deformation into asymmetric deformation. Compared with the thin-walled metal tubes, the lateral impact load, energy absorption and specific absorbed energy of foam-filled tubes were all enhanced distinctly. Geometries of tubes, density of aluminum foam and impact velocity all have effects on them to some extent.