BEHAVIOR OF CLOSED-CELL ALUMINUM FOAM UNDER IMPACT LOADING AS ENERGY ABSORBER

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. For rear end car impacts, the, energy absorption plays an important role because the impact energy is absorbed by bumper beam (structure) in the form of strain energy by deformation. This deformation at constant plateau stress is achieved by closed-cell aluminum foam. Along with this, the stiffness and the light weight are characteristics of aluminum foam. These good qualities of foam have better future in the field of material science and engineering. 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. Dissertation work focused on finite element method and analysis of RUC model of closed-cell aluminum foam under impact loading. SHELL-163, 4 noded element was used for modeling closed-cell foam made up of 6061 aluminum alloy. Cell thickness and relative density have been investigated for energy absorption during impact. Automatic surface to surface contact has been used to avoid penetration of material into each other. Results showed good characteristics of RUC model with respect to energy absorption and average plateau stress. Effects of nodal plastic strain and resultant acceleration showed that they were dependant on cell geometry. The effective plastic strain for different elements with respect of time proved the resultant acceleration. depend on initial elements and reduced along circumferential direction. It is observed that the stiffness affect the element displacement before actually getting displaced. All results including FE simulations and time-history plots show that the energy absorber made up of closed-cell aluminum foam will have considerable potential for offering increased' protection against neck injuries in low-velocity rear end vehicular impact.