| The effect of vehicle rail geometry on the crashworthiness behavior was studied using an explicit finite element code, LS-DYNA 970. There are three parts in this paper. Firstly, the mean force and energy absorption response of various cross-sectional geometries (cylindrical, squared, hexagonal, octagonal, tapered and top-hat thin-wall tubes of a constant cross-sectional area and length) are compared under the same dynamic axial impact loading, and the results indicated that the cylindrical section has great potential for enhanced energy dissipation providing a stable ring wrinkling mode can be developed. The second part studies the process of wrinkling development of the round tubes, which shows three modes of crushing deformation, i.e. the axi-symmetrical wrinkling with simultaneous ring expansion/contraction, the polygonal wrinkling with phase-alternative sequential folding, and the longitudinal buckling/displacement. The geometrical parameters of the round tube affecting these crushing modes and their transition were investigated. In the third part, the method to promote the high-energy dissipation mode---the stable axisymmetric ring wrinkling was studied. The initially corrugated tubes were used for stimulating stable wrinkle development upon collapse, and the effect of the geometrical features (wavelength and amplitude) on the specific energy dissipation under dynamic axial impact loading are studied. Based on these studies, the guidelines on vehicle rail crush initiator design and optimization is discussed. |
