安全帽對於機車騎士的保護功效已是無庸置疑的事實，然而有些文獻指出，穿戴安全帽於車禍發生時，因安全帽所引起之慣量卻會增加頸椎傷害的可能。近期，美國國家工程研究院院士金廣平博士申請一專利，在帽殼(Shell)及吸收衝擊墊料(Energy-absorbing Liner)之間添加另一材質，藉由添加材質低黏滯性的相對滑動，應可有效改善穿戴安全帽於車禍發生時所引起之角加速度，進而降低頸椎受傷害的可
能。本研究利用有限元素法分析帽殼與吸收衝擊墊料介面動態之效應，對金博士之假說進行驗證。
研究結果顯示，在降低安全帽帽殼與吸收衝擊墊料介面摩擦係數至零時，不僅可降低頭部所受之最大角加速度，更可有效降低HIC值及最大線性加速度，但若摩擦係數大於0.1 時，則降低效果不明顯，而如何提供一個小於0.1 摩擦係數的介面，將是下一個挑戰。

There is no doubt that the motorcycle helmet could protect the rider from head injuries during impact. However, some studies showed that it might increase neck injury due to helmet inertia in motorcycle accident. Recently, a patent filed by Dr. King A.I. suggests that reduce the friction between shell and liner by providing a low visco interface material could reduce the (flexion) angular acceleration of the head these reduce the injury risk. This study analyzes the helmet dynamic effect of interface between liner and shell by finite element simulation, in order to verify the
hypothesis of Dr. King. The result showed that when the friction coefficient on the interface between liner and shell was reduced to zero, the angular acceleration, the
linear acceleration as well as the HIC value all could be effectively reduced. However, when the friction coefficient was great than 0.1, the effect would be not significant. How to provide a interface between liner and shell with friction coefficient less than 0.1 would be a challenge.

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