隨著車輛工業的進步以及普及，在人口密集的都市裡，行人車禍的發生越來越頻繁，其中又以下肢傷害占了非常大的比例。下肢傷害需要非常久的時間復原以及不斷的復健，且伴隨著永久傷殘的可能，因此行人下肢保護的議題不容忽視。在車輛安全逐漸受到重視的現代，各國都已經建立了相關的法規以約束車輛製造商在相關方面的重視，因此許多車輛都已經裝備有保險桿系統的安全設計，例如柔軟的保險桿以及用於吸收能量的泡棉。儘管如此，下肢傷害依然無法全面地避免，原因在於剛性遠高於人體下肢的車輛前保險桿樑，係碰撞過程中帶給人體傷害的主要來源。因此，本論文的研究宗旨在於改變保險桿樑的結構設計增加其吸能性，試圖降低給行人帶來的傷害，同時在低速碰撞的條件下能夠保持足夠的剛性以避免車體在低速撞擊意外中過於容易受損。
在研究過程中，本論文將會先決定一個保險桿樑的幾何型態，並且定義設計參數。接著使用變異數分析(ANOVA)的方式分析各參數之貢獻度，可以將貢獻度低的參數去除以簡化設計難度。而車輛結構的完整性與行人安全保護的問題本身就是一個經典的最佳化問題，故本論文就以碰撞時保險桿樑的能量吸收量以及塑性變形量作為最佳化問題的兩個目標函數。
但是以經典力學的方式是幾乎不可能推導出結構設計參數與這兩個目標函數的關係式，因此本論文就以統計學中的克利金方法理論來進行響應曲面的建模工作。一旦建立完目標函數的定義，執行最佳化就變得非常可行。最後將本論的最佳設計進行高速下肢撞擊的有限元素模擬，以說明本論文之研究方法對於行人下肢保護帶來的改善程度。

Pedestrian car accidents have become more frequent in densely populated cities where lower extremity injuries with very large proportion, therefore, pedestrian lower extremity protection issue can’t be ignore. Many countries have established relevant regulation as constraint to automotive manufacture to force them value this issue. Thus, there have been many cars equipped safety design for bumper beam system. Nevertheless, lower extremity injury still can’t be absolutely avoided because of high stiffness of bumper beam which is far more than pedestrian lower limb’s. It’s the main source of the damage to human body during crash impact progress.
The main topic of this study is to improve the energy absorbing capacity of bumper beam by changing its geometry shape. Intend to decrease the damage to pedestrians and remain enough stiffness to avoid crush easily under low speed impact accident.
In this study, bumper beam cross-section shape will be defined first, as well its design variables. The choice between integrity of vehicle construction and pedestrian safety is a classical optimum problem, hence it’ll be defined the energy absorption and the plastic deformation of bumper beam during crash impact progress as two objective function for optimization.
In this study, the task of modeling response surface will be developed by Kriging method theory which is a branch of geostatistics. Then optimization can be implement. Finally, high speed lower extremity impact test will be implemented via finite element simulation with the optimum design, to evaluate the improvement of the protection for pedestrian lower extremity.

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