臺灣博碩士論文加值系統

保險桿位於車輛前後端，於車輛撞擊時，可以緩和衝擊力，保護及減輕車內乘客或陸上行人的傷害。本論文針對保險桿以無網格法做模擬分析及最佳化設計。
研究中，以Hyperworks和LS-Dyna為建模及分析軟體，對保險桿幾何建立模型後，利用傳統有限元素法及無網格法先後對保險桿進行準靜態模擬，並將分析結果與實驗比較，瞭解有限元素法與無網格法之間的差異，最後利用LS-OPT軟體對保險桿做最佳化。
本研究結果顯示無網格法，求解所需時間約為有限元素法的3~5倍，無網格法的分析結果較有限元素法更接近實驗值。在高速碰撞下，物件承受大變形，有限元素法因大變形，容易造成網格扭曲，導致準確度降低，無法收斂而至運算終止；而無網格法並無實質的元素或網格，沒有一般有限元素法因元素網格大變形扭曲而運算發散的情形，適合大變形之實務應用。研究中，對保險桿前端吸能材的厚度及短樑稈件厚度做最佳化，保險桿重量減輕5公斤，衝擊指數降低30%以上，撞擊剛性牆反力減少41%，撞擊後入侵乘坐空間的量也減少4%。

Bumpers are located at the front and rear of a vehicle. They are one of the major components absorbing impact energy to prevent passengers or pedestrians from harming. This paper utilized element-free method to analyze and improve the design.
In the study, HyperMesh was used for preprocess, and LS-Dyna was used for meshfree analysis. The analysis results of traditional finite element method and meshfree method were compared with the quasi-static crush tests. Optimization was perform to improve the functional performance.
The results show that the meshfree method required 3-5 times more of calculation time than tradition finite element method, but had better correlation with hardware testing than the finite element method. While under high speed impact and large deformation, traditional finite element method could experience element distortion and lead to computation divergence and terminate the analysis. The meshfree method does not have elements or meshes, and is suitable for large deformation analysis. A bumper design optimization was performed with 5 Kg weight reduction, impact index reduced 30%, rigid wall reaction force was redesigned by 41% and passenger residual space was improved 4%.

目 錄

中文摘要 i
英文摘要 ii
誌 謝 iv
目 錄 v
表目錄 viii
圖目錄 ix
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 1
1.3 研究動機 6
1.4 論文架構 7
第二章 無網格法理論 8
2.1 有限元素法之基本理論 8
2.1.1 直接勁度法(The direct stiffness method) 8
2.2 無網格法之基礎理論 10
2.2.1 最小移動二乘法(MLS) 11
2.2.2 葛勒金弱式 13
第三章 電腦輔助模擬建模 15
3.1 模擬架構 15
3.2 幾何建模 16
3.3 網格設定 20
第四章 材料試驗 21
4.1 實驗目的 22
4.2 實驗機台 23
4.3 抗壓實驗 25
4.4 三層材料抗壓試驗 30
4.4.1 材料與實驗 31
第五章 分析與實驗驗證 33
5.1 .LS-Dyna材料卡片介紹 33
5.2 橡膠模擬分析 37
5.3 蜂窩鋁模擬分析 40
5.4 .EPP泡沫模擬分析 44
5.5 三層材料模擬分析 47
5.5.1 三層材料-EFG法放大網格 50
第六章 碰撞模擬與分析 54
6.1 模型簡述 54
6.2 材料設定 55
6.3 前碰撞模擬分析 61
6.3.1 .Baseline保險桿設計 61
6.3.2 修改後保險桿設計 64
6.4 小結 70
第七章 碰撞最佳化 71
7.1 最佳化函數 71
7.1.1 設計變數 71
7.1.2 限制條件 73
7.1.3 目標函數 76
7.1.4 三大設計函數 76
7.2 連續響應面法 77
7.3 最佳化結果 79
7.4 最佳化結果驗證 83
第八章 結論與未來展望 85
8.1 結論 85
8.2 未來展望 87
參考文獻 88
符號彙編 91

參考文獻

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