臺灣博碩士論文加值系統

本研究是利用電腦模擬沃斯回火球墨鑄鐵在熱處理之淬冷階段中之溫度場及熱應力之分佈及變化情形，即工件由沃斯田鐵化溫度淬冷至沃斯回火溫度時內部溫度場及應力場分佈情形。為了增加模擬的準確性，先著重於冷卻過程中之界面熱傳係數隨表面溫度變化情形之計算。
首先討論圓柱形試棒，以實際量測之內部特定點的冷卻曲線為數據，作分析計算求得界面熱傳係數，再以此熱傳係數當做邊界條件，並藉助ANSYS有限元素分析軟體反推圓柱內特定點之冷卻曲線，進而與實測冷卻曲線作比較，確認所計算之界面熱傳係數的準確性。
將每一個節點的溫度場轉換為負載輸入，在模型上給予固定及限制條件，執行ANSYS軟體後，我們可以得到工件所有節點及元素之熱應力資料及瞭解熱應力之分佈情形。
900-300℃及900-350℃沃斯回火球墨鑄鐵的界面熱傳係數最高值分別達11000及5000 W/m2℃，出現於表面溫度約400℃及600℃時。
基於實際考量，更進一步探討曲柄軸的沃斯回火處理。在電腦上建立尺寸較為接近之曲柄軸模型，實際去模擬淬冷過程中之冷卻狀況，繪出其溫度、溫度梯度及熱應力變化情形。此部份證實了，運用適當的熱傳係數及邊界條件作為電腦模擬複雜工件於沃斯回火淬冷階段之熱傳及熱應力分析有其可行性。
沃斯回火球墨鑄鐵的應力，圓柱型試棒最高值可達到400MPa，曲柄軸最高應力值可達到575MPa，這個數值可能已超過彈性變形之極限。

This study investigated the distribution and changes of the temperature and thermal stress of austempering process of ductile iron during quenching stage by computer simulation. That is the distribution of the temperature and thermal stress of workpiece which was quenched from austenitizing temperature to austempering temperature. In order to increase the accuracy of simulating, the main work of this thesis was to calculate the surface-temperature-depending heat transfer coefficients during quenching stage.
At first, a cylinder specimen was investigated, the cooling curves were measured at specific locations inside the cylinder. Through the analysis and calculation of the measured data, the interface heat transfer coefficients were obtained. Then use these data of heat transfer coefficients as the boundary condition, the cooling curves at that specific points inside the cylinder were calculated by running the "ANSYS" software. The simulated curves were compared with the measured ones to confirm the accuracy of interface heat transfer coefficients.
The temperature field at each node was loaded as input together with constrains on model. After running the "ANSYS" software, we can obtained the thermal stress of the model at each node and element to understand the distribution of the thermal stress in the model.
During 900℃ to 300℃ and 350℃, the interface heat transfer coefficients of austempering process of ductile iron is about 11000W/m2℃ and 5000W/m2℃ when the surface temperature is around 400℃ and 600℃.
For an example of practical application, the heat transfer of austempering of a crank-shaft workpiece was studied. The solid model of the shaft of the near size was built by computer and then simulating the cooling process during quenching stage. The changes of the temperature, thermal gradient and thermal stress with time were plotted. This part of study proves the feasibility of the computer-simulation on heat transfer during quenching stage of complex workpiece.
The maximum thermal stress of ductile iron during quenching of austempering was 400 and 575Mpa for cylinder and crank-shaft respectively. Both values are possible over the limit of elasticity.

中文摘要……………………………………………………………………I
英文摘要……………………………………………………………………III
誌謝…………………………………………………………………………V
目錄…………………………………………………………………………VI
圖表索引……………………………………………………………………IX
符號索引……………………………………………………………………XIII
第一章 前言………………………………………………………………1
第二章 原理及文獻探討…………………………………………………3
2.1沃斯回火球墨鑄鐵之簡介…………………………………………3
2.2球墨鑄鐵之沃斯回火熱處理………………………………………4
2.3冷卻速率快慢的影響………………………………………………4
2.4合金元素銅、鎳、鉬對波來鐵生成時間的影響…………………5
2.5熱傳控制方程式及邊界條件………………………………………5
2.6有限差分法計算h值………………………………………………7
2.7界面熱傳現象………………………………………………………7
2.8熱處理應力與熱處理變形…………………………………………8
2.8.1基本的殘留應力…………………………………………………..9
2.8.2熱處理變形…………………………………………………………11
2.9有限元素分析軟體…………………………………………………12
2.10 Element type 的定義………………………………………………13
2.11Solution 階段………………………………………………………14
2.12Seqv定義………………………………………………………..…15
第三章 實驗方法…………………………………………………………16
3.1研究流程……………………………………………………………16
3.2探頭試棒的冷卻曲線………………………………………………16
3.3界面熱傳係數h的求法……………………………………………17
3.4試棒之成份及熱物理性質…………………………………………18
3.5ANSYS分析流程………………………………………………….19
3.5.1 模型的建立…………………………………………………………19
3.5.2Element Type的選擇………………………………………………20
3.5.3Element Size的選擇 ……………..………………………………20
3.6測溫探頭之溫度場模擬……………………………………………20
3.7測溫探頭之溫度梯度………………………………………………21
3.8測溫探頭之應力場模擬……………………………………………22
3.93D曲柄軸之溫度場模擬…………………………………………23
3.103D曲柄軸之溫度梯度……………………………………………23
3.113D曲柄軸之應力場模擬…………………………………………24
第四章 結果與討論………………………………………………………26
4.1 圓柱測溫探頭之熱流場………………….…………………………26
4.2 溫度量測曲線得影響…………………………………………………26
4.3 鹽浴熱傳導的影響……………………………………………………27
4.4 界面熱傳係數隨表面溫度的變化趨勢………………………………27
4.5 試棒溫度模擬與量測之比較……………………..…………………28
4.6 圓柱探頭試棒溫度場模擬……………………………………………28
4.7 圓柱型測溫探頭之應力場模擬………………………………………29
4.8 曲柄軸淬冷之溫度分佈特性及冷卻歷程……………………………30
4.9 曲柄軸淬冷之溫度梯度分佈…………………………………………31
4.10 曲柄軸淬冷之熱應力分佈特性及剖面……………………………31
4.11 降伏強度……………………………………………………………32
第五章 結論與建議………………………………………………………34
參考文獻……………………………………………………………………36
附錄A：有限差分法之推導公式…………………………………………83
附錄B：有限差分法求h之MATLAB程式………………………………85
附錄C：ANSYS模擬測溫探頭C19030……………………………………90
附錄D：ANSYS模擬測溫探頭C19035……………………………………94
附錄E：ANSYS模擬曲柄軸………………………………………………98

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