Abstract
The car front bumper system needs to meet the requirements of both pedestrian safety and low-speed impact which are somewhat contradicting. This study aims to design a new kind of modular self-adaptive energy absorber of the front bumper system which can balance the two performances. The X-shaped energy-absorbing structure was proposed which can enhance the energy absorption capacity during impact by changing its deformation mode based on the amount of external collision energy. Then, finite element simulations with a realistic vehicle bumper system are performed to demonstrate its crashworthiness in comparison with the traditional foam energy absorber, which presents a significant improvement of the two performances. Furthermore, the structural parameters of the X-shaped energy-absorbing structure including thickness (t u), side arc radius (R), and clamping boost beam thickness (t b) are analyzed using a full factorial method, and a multiobjective optimization is implemented regarding evaluation indexes of both pedestrian safety and low-speed impact. The optimal parameters are then verified, and the feasibility of the optimal results is confirmed. In conclusion, the new X-shaped energy absorber can meet both pedestrian safety and low-speed impact requirements well by altering the main deformation modes according to different impact energy levels.
Highlights
The front car bumper system is a complex energy-absorbing system in a car design [1] which must meet both the requirements of pedestrian safety [2, 3] and low-speed impact [4]
Taking the foam bumper energy absorber as an example, the absorber satisfying the low-speed impact well can be generally too stiff when considering the impact with pedestrian lower extremities due to the high force level
This paper proposes and designs a new conceptual type of bumper energy absorber in a multioptimization method considering the requirements of both pedestrian safety and low-speed impact, which adopts a modular design in the form of assembling with an X-shaped unit
Summary
The front car bumper system is a complex energy-absorbing system in a car design [1] which must meet both the requirements of pedestrian safety [2, 3] and low-speed impact [4]. The bumper system design requirements of pedestrian safety and low-speed impact are somewhat contradicting regarding force and impact energy levels. Taking the foam bumper energy absorber as an example, the absorber satisfying the low-speed impact well can be generally too stiff when considering the impact with pedestrian lower extremities due to the high force level. The traditional energy absorbers are usually an integrated structure made of thermoplastic polymer or foamed polypropylene (EPP) which could need an overall replacement due to a local damage
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