AZ91D鎂合金薄殼之熱變形模擬與控制

Numerical Simulation and Control of Thermal Deformation in AZ91D Magnesium Alloy Frame Shell

陳憲銘(Hsien-Ming Chen)

指導教授 ： 陳貞光

國立臺北科技大學/工程學院/材料及資源工程系研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00567

摘要

隨著電子產品輕薄短小的趨勢，而新的產品材料特性：電磁波干擾、散熱性，皆使塑膠材料無法滿足，鎂合金輕金屬具可回收性之優點，因而逐漸受到重用。其中產品受到溫度影響之熱變形為評估產品結構壽命之重要因素，同時可作為產品設計與造型之參考。
因此本研究利用電腦輔助工程軟體ANSYS結合有限元素法來模擬AZ91D鎂合金薄殼結構體在溫度極高與極低的溫度場時因熱膨脹係數的差異而產生熱變形，控制不同尺寸、厚度的參數變異，在高低溫度環境中所產生的熱變形量。接著探討在結構體加強輔助肋受熱變形的差異性，以肋的尺寸大小及厚度做為田口法實驗設計的控制因子，每一因子皆選擇3個實驗水準，並以熱變形量與肋重做為品質特性來討論。應用田口法L9(34)直交表規劃與建立模型，再以ANSYS模擬其最大熱變形量，研究結果發現熱變形受薄殼尺寸影響最為顯著，在熱變形的控制方面，肋的高度控制對於熱變形的改善與輕量上影響最大，其結果顯示，以有限元素軟體結合田口實驗法可做為後續產品建立鎂合金薄殼之較佳設計，以縮短產品開發之時間。

關鍵字

有限元素分析 ； 鎂合金AZ91D ； 熱變形 ； 田口實驗設計法

並列摘要

Magnesium alloy products are superior to plastic materials in many aspects including their lightweight, electromagnetic interference property, high specific strength, and recyclability. The 3C applications often require them to be die cast into thin shells. These shells are subject to thermal deformation due to temperature increase in use.
In this study, computer aided engineering software ANSYS combined with finite element method is utilized to simulate the thermal deformation of AZ91D magnesium alloy shell structure. The simulations consider the changes in shell sizes, shell thickness, and temperatures. It is found that there exists a critical shell thickness of 1mm above which the thermal deformation remains nearly constant. Whereas the thermal deformation raises greatly with shell area indicating the importance of thermal deformation upon shell size design.
In order to control the thermal deformation, this study considers adding ribs to reduce structure deformation. L9 (34) orthogonal array of Taguchi method is used to minimize the thermal deformation and rib weight for discussions. It is found that the rib height and thickness are the main controlling factors in rib design for thermal deformation. Ribs are effective in reducing the deformation at the side of shell surface with the ribs. On the side of shell surface that does not have the ribs, very limited deformation reduction is observed.

並列關鍵字

Finite Element Analysis (FEA) ； Magnesium alloys ； Thermal deformation ； Taguchi’s method

參考文獻

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