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題 名 | A Simple Model for Sand Casting Mechanisms=砂模鑄造之簡單模式分析 |
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作 者 | 趙隆山; 林文彬; 薛千山; | 書刊名 | 中國機械工程學刊 |
卷 期 | 19:5 1998.10[民87.10] |
頁 次 | 頁531-542 |
分類號 | 472.2 |
關鍵詞 | 砂模鑄造; 簡單模式分析; Sand casting; Heat transfer; Modeling; |
語 文 | 英文(English) |
中文摘要 | 砂模的低熱傳導性,使得金屬鑄件的凝固需要較長的時間,並使得砂模的溫度梯 度較鑄件部分高。於數值分析時,需要較密的格點,使得大部分的計算時間和記憶空間,用 在較不感興趣的模砂上。 本文針對上述問題,使用邊界曲率法建立了砂模 / 鑄件間的等效 熱傳係數對不同曲率半徑之關係資料庫,在作凝固分析時,不需考慮砂模,而直接計算鑄件 之熱邊界條件。 本研究建立兩種資料庫,分別是考慮砂模與鑄件間接觸熱阻的效應 (H) 與 不考慮 (H)。本文是以有限差分法來作數值分析,於矩形鑄件之測試中,發現由浮力效應所 導致之金屬液流動對溫度場的影響並不顯著,因此在分析中可以忽略其效應。同時邊界曲率 法比起考慮砂模之計算可節省高達 84% 之電腦計算時間。 本文更進一步以 Brandt 等人的 L 形鑄件之實驗結果,來比較砂模與鑄件間接觸熱阻的影響,及整個模式的正確性。計算和 實驗結果相互比較相當吻合,但考慮接觸熱阻的 H 得到較佳的結果。 最後應用座標轉換將 此模式推廣應用在不規則形狀鑄件的熱傳分析,本研究以板手形之鑄件來作為測試,得到蠻 合理之結果,如此可證實此模式可應用於實際鑄件之凝固分析。 |
英文摘要 | The low thermal conductivity of a sand mold can result in longer casting time and higher temperature gradient, and thus a denser mesh in the mold than in the metal is usually required for numerical heat transfer analysis. Most computing effort is spent on the mold solution that is of less interest. If the solidification problem of a casting process can be solved without explicitly handling the heat transfer in the mold, the computing cost can be reduced substantially. In this paper, a mathematical boundary curvature method is set up to replace the effect of the sand mold by an equivalent coefficient of heat transfer. Two data bases of the coefficient versus timedependent curvature are built for both considering the contact resistance (between the sand mold and the metal) and not. The finite difference method is used to solve the heat transfer problems. The source term method is employed to deal with the nonlinear term of latent heat. A rectangle casting was used to test the model. As compared to the result of having the mold enmeshed, the proposed model saves the computing time up to 84%. It was also found that the flow field induced by natural convection has little effect on the temperature distribution of liquid metal. To further testify this model, the experimental result of an L-shape casting was used to compare with the computing ones for two sets of the equivalent heat transfer coefficient. The computing results are similar to those of the experiment. It is shown that the one with contact resistance has the better result than the other one without the resistance. Finally, the method is modified to handle the casting of irregular shape and verified by a wrench-shape casting problem. |
本系統中英文摘要資訊取自各篇刊載內容。