Abstract
With a view to examine the axial crushing behavior of thin-walled tubes, which form the parts of transports such as aircrafts and automobiles, under dynamic compressive loads, a series of numerical simulations for thin-walled circular tubes of various dimensions was carried out by using the explicit FEM code LS-DYNA. The energy absorption efficiency and the bifurcation conditions of the collapse modes of these tubes subjected to dynamic axial compression were primarily investigated. In order to confirm the validity of the simulations, first, some calculated results such as the load - displacement relation, the collapse behavior, the absorbed energy per unit volume, and so forth by using the axisymmetric FE model were compared with those obtained by way of experiment under the corresponding condition. Here, the absorbed energy per unit volume was formulated on the basis of Alexander's theory and the Johnson-Cook model, and the results obtained by this formulation were compared with the corresponding results obtained by the simulations and experiments for many tubes of various dimensions. Next, the effects of the initial imperfection and the inertial force on the bifurcation of the axial-collapse mode were examined by using the 3D-shell model. It was clarified that the mode of the dynamic progressive buckling was affected by the natural vibration mode.
