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研究生:謝國良
論文名稱:鎢基穿甲複合材料在高溫及高速荷載下之塑變行為分析
論文名稱(外文):The plastic deformation behaviour of tungsten-nickle-iron composite subjected to high temperature and high strain rate loading conditions
指導教授:李偉賢李偉賢引用關係
學位類別:碩士
校院名稱:國立成功大學
系所名稱:機械工程學研究所
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:1997
畢業學年度:85
語文別:中文
論文頁數:93
中文關鍵詞:鎢基穿甲複合材料塑變行為
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本文是利用以一維彈性波理論為基礎的霍普金森動態材料試驗機,配合加熱裝置,對鎢基複合材料(W-Ni-Fe)做高溫及高速荷載之塑變行為分析;實驗條件為溫度從25℃到1100℃、應變速率從800 s-1到4000 s-1之間。由實驗結果分析,可得到材料之應力-應變關係圖;再對材料做微觀組織分析(OM)及破壞材料之破斷面觀察(SEM)。配合巨觀與微觀之分析結果,我們引介一材料變形統制方程式,來描述此材料之塑變行為,以作為工程設計上之用。
由實驗結果得知,W-Ni-Fe複合材料之機械性質受溫度與應變速率的影響很大。隨著應變速率的提高,塑流應力亦跟隨著上升;但在應變速率4000 s-1以上時,塑流應力會先上升再下降。而溫度的上升,使得塑流應力明顯下降。我們可從材料之加工硬化值、應變速率敏感性及溫度敏感性,觀察這些參數影響程度。由微觀分析可發現,隨著應變速率及溫度的上升,裂縫的數目越多,晶粒的變形量也越大。而裂縫增加到一定程度時會集結,並受應力作用串連在一起,最後造成材料破壞,反而使塑流應力下降。從破斷面觀察可知,此材料裂縫會在鎢晶粒、鎳-鐵基地、鎢-鎢晶界及鎢-鎳鐵邊界發生。結合微觀與巨觀結果,以Zerilli-Armstrong模式之統制方程式,可準確的描述W-Ni-Fe複合材料在高溫及高速下的塑變行為,提供設計與模擬之用。


The purpose of this study is to investigate the plastic deformation behaviour of Tungsten-Nickel-Iron (W 92.5 wt%+Ni 5.25 wt%+Fe 2.25 wt%) composite subjected to high temperature and high strain rate loading conditions. The mechanical testing is performed under strain rate ranging from 800 s-1 to 4000 s-1 andconstant temperatures in range of 25℃ to 1100℃ by means of a split-Hopkinson bar which is developed based on one dimensional elastic wave propagation theory. The tested temperatures are obtained by enclosing the specimen in a clam shell radiant-heating furnace. The O.M. and S.E.M. techniques are also used to analyze the fracture and microstructure characteristics of the deformed specimens. With the macroscopic and microscopic results, a constitutive equation is used to describe the plastic deformation behaviour of the material.
 The experimental results indicate that the temperature and strain rate are influences on the mechanical properties of material. Flow stress increases with strain rate, but decreases with temperature. At the highest strain rate of 4000 s-1, flow stress increases firstly up to strain of 20%, then decreases rapidly with the augmentation of strain. The strain rate andtemperature sensitivities and work hardening coefficient change with the variety of strain, strain rate and temperature. From the microscopic analyzing, it is found that the microcrack densities and grain deformation parameter increase with the augmentation of strain rate and temperature. The material fracture includes four kinds of model: tungsten cleavage, matrix failure, tungsten-matrix separation and tungsten-tungsten grain boundary failure. Finally, by comparing the results of mechanical testing with those of Zerilli-Armstrong equation for BCC structure, the agreement between the experimental and simulated data was excellent.

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