| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 96 === Fatalities related to pedestrian accidents contribute a large proportion of all traffic accidental deaths. Previous studies show that more than 50% of pedestrian fatalities are caused by head injuries and most of them are impacted by engine hood or windshield. In order to prevent the human life loss due to car-pedestrian collisions, passive safety devices to lower the possibility of head injury has been proposed in industry recently. Among them are pop-up hood systems and outside airbags, etc. In this study, the improvement of the current pop-up hood is our main focus.
The pop-up hood system lifts up the rear part of the hood for a distance at the time when the car-pedestrian impact happens and provides a free space between the hood and the hard components underneath the hood. As the head of pedestrian impacts to the hood, free space of pop-up hood allows the hood to deform and absorb most of the impact energy through structural deformation. The system, as a result, is capable of reducing the head injury with its structural deformation. However, some area of the structure, such as supports, still keeps its high stiffness after the hood is popped up, and it might still cause high risk of head injury. Therefore, such phenomenon is analyzed and a new pop-up hood system to improve the high-HIC-valued area is developed in this thesis. This pop-up system is designed with a newly driving mechanism and spring-damper system to reduce the high stiffness of the original hood structural support. For validation, the numerical tests based on Euro-NCAP are conducted to evaluate the performance over the complete area of the hood system.
The study is departed into 3 stages. In the first stage, the finite element model of the headform impactor and the car front structure are created and validated. In the second stage, the numerical tests based on Euro-NCAP are simulated and the performance of the original and the new pop-up hood system are analyzed and compared. The three design parameters for the new pop-up hood systems, hood lift-up height, supporting spring stiffness and damping coefficient, are also analyzed. In the last stage, pop-up mechanism for the new pop-up hood system is designed and tested with rigid-body dynamics. Finally, conclusions and suggestions of this study are summarized in the last part of the thesis.
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