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| 題 名 | Transition from Linear to Nonlinear Viscoelasticity during Deformation in a Zr-based Glassy Alloy=Zr基非晶合金在變形中從線性到非線性黏彈性的轉變 |
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| 作 者 | 陳鶴壽; | 書刊名 | 華岡工程學報 |
| 卷 期 | 14 2000.06[民89.06] |
| 頁 次 | 頁161-180 |
| 分類號 | 440.39 |
| 關鍵詞 | Zr基非晶合金; 線性黏彈性; 非線性黏彈性; Glassy alloy; Glass transition; Viscoelasticity; Viscous flow; Stress-induced structural relaxation; |
| 語 文 | 英文(English) |
| 中文摘要 | 本文研究Zr基非晶合金於接近玻璃轉換溫度下,黏彈性在等應變速率下從線性到非線性的轉換行為,並於根據fictive stress的觀念提出數學模式。實驗結果顯示,因為Zr基非晶合金的原子結構很簡單,所以其黏彈性行為具有很窄的鬆弛時間分佈。因此,在穩定態牛頓流體與非牛頓流體之間的轉變,可以應變速率的stretched exponent鬆弛函數而加以分析。Zr基非晶合金在發生轉變現象的情況可用一種新的模式來敘述,此模式是建立在應力引發之結構鬆弛及一種間接表達材料結構的fictive stress之觀念的假設上。從此模式所求得之應力-應變曲線與實驗數據相當吻合。於足夠高的應變速率下,此模式所計算得到在非線性的黏彈性區域之應力-應變曲線顯現一種應力震盪現象。在許多高分子材料中早已觀察到這種應力震盪現象,但是在非晶材料中仍未被報導。在Zr基非晶合金的應力震盪現象被觀察到,且如數學模式所預測之一般。 |
| 英文摘要 | The transition behaviors from linear to nonlinear viscoelasticity during constant strain-rate deformations of a Zr-based glassy alloy near the glass transition temperature are investigated and a model calculation based on concept of a fictive stress is performed. The experimental results show that the viscoelastic behavior of the glassy alloy is characterized by a very narrow relaxation-time distribution due to its simple atomic structure. Hence, the transition between steady-state Newtonian and non-Newtonian flows can be analyzed by a stretched exponent relaxation-function of strain rate. And the condition at which the transition occurs in the Zr-based glassy alloy is investigated with a new model proposed on the basis of the hypothesis of stress-induced structural relaxation and concept of fictive stress that expresses the structure of the material indirectly. Stress-strain curves calculate from the modl agree quantitatively well with experimental results. The calculated curves of sufficiently higher strain-rates in the nonlinear viscoelastic regime show a stress-oscillation. This has been observed in many polymers, but has not been reported previously in glassy alloys. In the Zr-based glassy alloy, the oscillation is observed as predicted by the model. |
本系統中英文摘要資訊取自各篇刊載內容。