Transition from Linear to Nonlinear Viscoelasticity during Deformation in a Zr-based Glassy Alloy

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题名:	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
作者:	Kato, Hidemi Kawamura, Yoshihito Inoue, Akihisa 陳鶴壽
贡献者:	華岡工程學報
关键词:	glassy alloy glass transition viscoelasticily viscous flow stress-induced structural relaxation
日期:	2000-06
上传时间:	2014-11-03 14:26:35 (UTC+8)
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爲，並於根據fictive stress的觀念提出數學模式。實驗結果顯示，因爲Zr基非晶合金的原子結構很簡單，所以其黏彈性行爲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蕩現象被觀察到，且如數學模式所預測之一般。 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 a concept of fictive stress that expresses the structure of the material indirectly. Stress-strain curves calculated from the model 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.
關聯:	華岡工程學報； 14 期 (2000 / 06 / 01) ， P161 - 180
显示于类别:	[College of Engineering] Chinese Culture University Hwa Kang Journal of Engineering

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