臺灣博碩士論文加值系統

基於安全考量，汽車結構強度均需通過測試，為了減少測試次數及縮短開發時程，國際各大車廠均有採用電腦輔助工程(Computer-Aided Engineering，CAE)分析技術從事汽車結構強度設計。
本論文即是建立以CAE進行汽車局部結構強度分析之分析技術。在研究方法上，選定引擎蓋及散熱器支架為研究載具，以有限元素軟體LS-DYNA作為分析工具，進行汽車局部結構CAE分析技術之建立。
對於有限元素模型之建立方法，針對CAD (Computer-Aided Design)圖檔與CAE的轉換問題，網格資料建立時元素大小的考量，各個零件間的組裝方式，以及引擎蓋轉軸機構與引擎蓋卡勾鎖扣機構的模擬模型建立方式提出說明。
模擬分析方面，說明初始穿透問題會造成應力上升的不合理現象，零能模式造成的影響及控制方法，以及如何適當使用質量比例因子來加快模擬運算速度。
最後利用所建立之有限元素模型，進行引擎蓋自由落下撞擊散熱器支架之受力分析。本論文之研究成果可提供進行CAE汽車結構分析時之參考。

The structural strength of automobiles must pass through tests due to safety concern. In order to reduce the time of tests and shorten the developing period, automakers have decided to adopt the CAE (Computer-Aided Engineering) technology to analyze the strength of automobiles.
This paper analyzes the strength of automotive sub-structures with the assistance of CAE technology. Using the finite element code, LS-DYNA, the analysis technique for the engine hood and radiator support frame has been built.
In regard to the method for building finite element model of automobiles, including the weak convertibility between CAD (Computer-Aided Design) and CAE files, the selection of mesh size, the assembly of parts, the hinge mechanism of engine hoods, and the lock-striker model.
This paper also discusses about the influence of initial penetration, usage of hourglass control and mass scaling.
Eventually, using the built finite element model, the free fall of the engine hood has been analyzed.

目錄
目錄---------------------------------------------------------------------iii
圖目錄 -----------------------------------------------------------------vi
表目錄 --------------------------------------------------------------ix

第一章 緒論 ----------------------------------------------------------1
1.1 前言 ---------------------------------------------------------1
1.2 研究動機與目的 --------------------------------------------2
1.3 文獻回顧 ----------------------------------------------------3
1.4 研究方法與步驟 ---------------------------------------------------6
1.5 論文總覽 ------------------------------------------------------------8
第二章 研究載具及分析軟體簡介 ---------------------------------10
2.1 研究載具介紹 -----------------------------------------------------10
2.2 有限元素模擬軟體簡介 -----------------------------------------13
2.3 顯性積分法 --------------------------------------------------------16
第三章 汽車局部結構模擬模型之建立 ---------------------------20
3.1 CAD圖檔與有限元素軟體之介面轉換 ----------------------20
3.1.1 CAD圖檔與前處理軟體之轉換 -----------------------20
3.1.2 CAD圖檔轉檔問題 --------------------------------------21
3.1.2 CAD檔案過大之問題 -----------------------------------23
3.2 網格資料之建立 --------------------------------------------------24
3.2.1 元素大小的決定 ------------------------------------------24
3.2.2 模型簡化原則 ---------------------------------------------25
3.2.3 網格資料組合方法 ---------------------------------------29
3.3 零件組合及連接 --------------------------------------------------30
3.4 引擎蓋轉軸機構模擬模型 --------------------------------------32
3.5 引擎蓋卡勾鎖扣機構模擬模型 --------------------------------35
3.6 其他模型及設定 --------------------------------------------------38
3.6.1 橡膠及卡勾 --------------------------------------------------38
3.6.2 邊界條件 -----------------------------------------------------39
3.6.3 材料性質------------------------------------------------------41
3.7 已完成之有限元素模型 -----------------------------------------41
第四章 模擬分析結果之探討 -------------------------------------43
4.1 初始穿透的影響 --------------------------------------------------43
4.2 零能模式之影響 --------------------------------------------------49
4.2.1 零能變形模式簡介 --------------------------------------- 49
4.2.2 零能模式之影響 ------------------------------------------ 51
4.3 質量比例之影響 --------------------------------------------------57
4.3.1 加入質量比例之模擬分析 ------------------------------58
4.3.2 質量比例因子之探討 ------------------------------------61
4.4 散熱器支架結構分析 --------------------------------------------63
4.4.1 散熱器支架之受力分析 ----------------------------------65
4.4.2 結果與討論 -------------------------------------------------70
4.5 有限元素模擬實驗驗證規劃 -----------------------------------70
第五章 結論 ------------------------------------------------------------------74
參考文獻-------------------------------------------------------------------------76











圖目錄
圖2.1 研究載具 ---------------------------------------------------------------11
圖2.2 引擎蓋之CAD圖檔 -------------------------------------------------12
圖2.3 引擎蓋轉軸機構之CAD圖檔 -------------------------------------12
圖2.4 散熱器支架之CAD圖檔 -------------------------------------------13
圖2.5 有限元素分析檔案處理程序 --------------------------------------14
圖3.1 CAD圖檔與實際零件 -----------------------------------------------22
圖3.2 修補後轉入前處理之CAD檔 -------------------------------------22
圖3.3 彎角處模型建立原則 -----------------------------------------------26
圖3.4 bead處模型建立原則 -----------------------------------------------26
圖3.5 孔洞處模型建立原則 -----------------------------------------------27
圖3.6 引擎蓋內板有限元素模型 -----------------------------------------28
圖3.7 網格資料組合方法 --------------------------------------------------29
圖3.8 實際零件之連接方式 -----------------------------------------------30
圖3.9 兩零件焊接-------------------------------------------------------------31
圖3.10 引擎蓋轉軸機構 ----------------------------------------------------33
圖3.11 引擎蓋轉軸機構模型 ----------------------------------------------34
圖3.12 引擎蓋卡勾鎖扣機構 ----------------------------------------------35
圖3.13 引擎蓋關閉時之鎖扣機構 ----------------------------------------36
圖3.14 鎖扣之CAD外形 ---------------------------------------------------36
圖3.15 鎖扣機構之模擬模型 ----------------------------------------------37
圖3.16 橡膠之模擬模型 ----------------------------------------------------38
圖3.17 引擎蓋卡勾 ----------------------------------------------------------39
圖3.18 完整之實物樣件 ----------------------------------------------------40
圖3.19 引擎蓋轉軸邊界條件 ----------------------------------------------40
圖3.20 散熱器支架與車身結構之邊界條件 ----------------------------40
圖3.21 完成之有限元素模型 ----------------------------------------------41
圖4.1 元素間的初始穿透情形 --------------------------------------------44
圖4.2 元素間的貫穿 --------------------------------------------------------44
圖4.3 難以發現之穿透現象 -----------------------------------------------45
圖4.4 初始穿透影響之模擬模型 -----------------------------------------46
圖4.5 有初始穿透造成初始應力 -----------------------------------------46
圖4.6 無初始穿透之模擬結果----------------------------------------------47
圖4.7 初始穿透對等效應力之影響比較----------------------------------48
圖4.8 殼元素變形模式 -----------------------------------------------------50
圖4.9 研究沙漏模式之模擬模型 -----------------------------------------51
圖4.10 模擬分析結果之能量曲線 ----------------------------------------52
圖4.11 沙漏能佔總能量之比例 ------------------------------------------ 52
圖4.12 模擬分析結果之能量曲線 ----------------------------------------53
圖4.13 全積分元素模擬結果 ----------------------------------------------54
圖4.14 總能量比較圖 ------------------------------------------------------ 55
圖4.15 內能比較圖 --------------------------------------------------------- 55
圖4.16 動能比較圖 ----------------------------------------------------------56
圖4.17 能量比較圖 ----------------------------------------------------------60
圖4.18 使用質量比例後之能量比較圖 ----------------------------------62
圖4.19 整體有限元素模型 -------------------------------------------------63
圖4.20 引擎蓋落下撞擊模擬結果 ----------------------------------------64
圖4.21 散熱器支架零件之等效應力分布圖 ----------------------------65
圖4.22 散熱器支架上橫桿等效應力分布圖 --------------------------- 66
圖4.23 大燈架受力後之等效應力分布圖 ------------------------------ 67
圖4.24 散熱器支架中桿部位等效應力分布圖 -------------------------68
圖4.25 散熱器支架下半部結構碰撞後之等效應力分布圖 --------- 69
圖4.26 應變量測實驗設備 -------------------------------------------------72
圖4.27 荷重計-----------------------------------------------------------------72
圖4.28 荷重計擺放位置-----------------------------------------------------73


表目錄
表3.1 FEMB與HYPERMESH所能接收之CAD檔案格式 ----------21
表3.2 前處理軟體對單一CAD檔案之限制 ----------------------------23
表3.3 一般鋼鐵之材料性質 -----------------------------------------------25
表3.4 整體模型元素總表 --------------------------------------------------42
表4.1 四邊形殼元素 --------------------------------------------------------49
表4.2 模擬運算時間 --------------------------------------------------------56
表 4.3 質量增加率比較 ----------------------------------------------------58
表4.4 時間增量與質量增加率 --------------------------------------------61

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