Abstract: In order to design structure of better impact potential for target vehicle， a finite element modeling used symmetry penalty method frequently was put forward to simulate two longitudinal rails schemes. Case 1 and 2 were separately appraised by three indexes including the vehicle deformation， deceleration and the passenger compartment intrusion: overall deformation is in line with the requirements in two cases. But because of induced slots， crumple deformation occurred in sequence from energy absorbing boxes to the longitudinal rails (from front to rear) during the impact in Case 2. Deceleration curves of Case 2 were also more consistent with principle of “the first step is taller and the second is lower” and the average passing force was more gently and cabin intrusions were less. Simulation results show that the design of longitudinal rail must have appropriate deformation guide to come true steady axial collapse mode. So the right deceleration curve of Case 2 was selected as the input value of occupant restraint system optimization.

Key words: vehicle structure, longitudinal rail, full frontal impact, simulation, scheme choice