Collapse Study of a Pair Thin-Walled Prismatic Column Subjected to Oblique Loads

In the design of vehicle structures for crashworthiness there is a need for rigid subsystems that guarantee an undeformable survival cell for the passengers and deformable subsystems able to efficiently dissipate the kinetic energy. The front rails are the main deformable components dissipating energy in a frontal impact, which is the most dangerous crash situation. In frontal impact these rails have the greatest influence on vehicle crash performance. In this work study of different cross sections of the front rails under full frontal crash with different inclination angle of barrier considering two connected or two separated rails is carried out. The present paper deals with the collapse simulation of two extruded polygonal section columns made of aluminum alloy which are separated or are connected with a nearly rigid bumper and, are subjected to oblique loads. Oblique load conditions in numerical simulations are applied by means of impacting a declined rigid wall on the tubes with no friction. The explicit finite element code LS-DYNA is used to simulate the crash behavior of polygonal section columns which are undergoing both axial and bending collapses situations. In order to validate LS-DYNA results the collapse procedure of square columns is successfully simulated and the obtained numerical results are compared with actual available experimental data. Mean crush loads and permanent displacements correspond to load angles have been investigated considering columns with square, hexagonal and, octagonal cross sections. It is shown that a pair of octagonal cross section connected columns has better characteristics from the point of view of crashworthiness under oblique load condition and connection between two rails dominates bending mode of deformation and reduces crashworthiness capability of front end of vehicle.