FINITE ELEMENT ANALYSIS AND DESIGN OF ENERGY ABSORBERS FOR REAR-END VEHICULAR IMPACT

Abstract

Neck injuries resulting from rear end car impacts have become a major problem in our society. These injuries are usually not life threatening but are one of the most important injury categories with regard to long-term consequences. This dissertation is mainly focused on the design of energy absorbers for vehicles undergoing low-velocity rear-end collisions. Results from accident research and biomechanical research emphasize the importance of acceleration pattern under collision and accordingly, energy absorbers with a particular focus on low and moderate impact severity have to be designed. Based on these interpretations new designs for energy absorbers have been proposed. Simulations of the performance of these designs using Finite Element analysis are presented as a part of an effort to improve protection against neck injuries. It is concluded that if an energy absorber is designed which can deform easily at the time of initial impact and provide more gradual deformation resulting in gradual impact then the possibility of whiplash injuries may be minimized. The primary goal of these absorbers will be not only to absorb high amount of energy but also to transfer the impact force from the car's exterior to the occupant's seat gradually rather than in the form of a sudden jerk. This can be achieved by controlled plastic deformation of the metallic energy absorber. The objective of the present work is to achieve this through solid modeling and using the non-linear, explicit dynamic code, LS-DYNA in the Finite Element software package ANSYS. The work is divided into two sections; firstly, to develop the numerical models of the energy absorbers and secondly, to modify them to get an optimum design suitable for reduced effect of the impact. Deformation behavior of the modified metallic energy absorbers are compared to those of the standard energy absorbers under the application of impact loading. All results, including FE simulations and time-history plots show that the modified designs will have considerable potential for offering increased protection against neck injuries in low-velocity rear-end vehicular impact.