Research And Development Of A Pop-up Engine Hood For Pedestrian Protection

The pedestrian protection is one of the important problems in passive vehicle safety area. Statistically, almost30%of pedestrians get head injury in car-pedestrian crash accidents. Furthermore, most pedestrian deaths occur due to the hard impact of head against stiff hood or windshield. If we dividing the car-pedestrian interaction area, we can see that1/3of them occur between head and engine hood. So it’s necessary to improve the pedestrian protection of engine hood. Pop-up engine hood is a very effective way to improve pedestrian head protection by expanding space and absorbing energy during in crash. This thesis will give a design of this engine hood and provide theoretical demonstration.First of all, A FE model of the headform impactor based on the National Pedestrian Protection Standard is built. By using this model, the effect of different connection of skin and sphere to the performance of the impactor is presented; also with the effect of different Material Parameter of the skin. Similarly, we can see how crash factor affect the impactor HIC value by using the model of head collision. Combining with crash depth factor which will also affect HIC value, the fundamentals of pop-up hood is provided.Secondly, proceed from the mechanism design theory; a set of active hood-lifting device based on link mechanism is designed. The multi-rigid-body dynamics simulation model of the hood-lifting system is built and the kinematics simulation of the system is carried. Take the speed of the hood lifting as the target; make the layout of the device in the engine cabin as the constraint, the optimization of the lifting system is carried. It is shown that the device can satisfy the design requirement and achieve the purpose of the pedestrian protection.Thirdly, the finite element model of a pop-up hood system is founded, and the performan-ce of pedestrian protection is studied. Simulation results indicate that the peak acceleration of headform impactor is decreased by25.1%, and injury HIC value is decreased by66.4%comp-ared to traditional hood under same conditions. Synergy of pop-up mechanism and material of the hood is also considered, and the pedestrian protection performance of aluminum pop-up h-ood is researched.Finally, a drop test platform is built to test the pedestrian protection performance of the engine hood. The confirmatory research of pedestrian protection performance of the pop-up hood is carried out. The experiment results showed that this pop-up hood can effectively improve the pedestrian head protection performance. Through the comparative analysis of the experimental and simulation result, the validity of the finite element model is verified.