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研究生：	陳婷容 Chen, Ting-Jung
論文名稱：	蜂巢與泡沫材料之潛變斷裂與潛變挫曲 Creep-rupturing and creep-buckling of honeycombs and foams
指導教授：	黃忠信 Huang, Jong-Shin
學位類別：	博士 Doctor
系所名稱：	工學院 - 土木工程學系 Department of Civil Engineering
論文出版年：	2008
畢業學年度：	96
語文別：	英文
論文頁數：	163
中文關鍵詞：	蜂巢、潛變、泡沫、挫曲、圓形蜂巢、斷裂
外文關鍵詞：	rupturing, buckling, honeycomb, creep, circular cell honeycomb, foam
相關次數：	點閱：79 下載：1
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細胞型材料，包括規則六角形蜂巢材料與開放型泡沫材料，於高溫環境下承受一固定應力作用時，潛變斷裂與潛變挫曲為兩種主要破壞機制。當細胞型材料於單軸拉應力作用下，潛變破裂為其主控破壞機制，本研究經由理論分析結果得知，細胞型材料之潛變破裂行為，乃遵循常見之Monkman-Grant關係式，而且此關係式中之參數，與其微結構及構成固體材料之潛變性質相關，同時，亦發現細胞型材料微結構中，具變剖面與曲度微構件之雙重微結構缺陷，其對潛變破裂行為之影響，遠大於單一微結構缺陷所造成者。另外，當細胞型材料承受單軸壓應力作用時，本研究亦理論推導其潛變挫曲之壽命，分析結果發現，細胞型材料發生潛變挫曲所需時間，與其相對密度及組成固體材料之潛變參數有關。此外，本研究探討當細胞型材料承受多少壓應力作用時，其破壞機制將由潛變挫曲轉成潛變斷裂，並藉由與實驗數據比較，以確認理論分析結果之正確性，進而發現細胞型材料之潛變挫曲與潛變斷裂，對其微結構缺陷非常敏感。最後，針對具完美微結構之圓形蜂巢材料，理論推導及數值計算其勁度、強度、彈性挫曲與潛變斷裂，並將分析結果與六角形蜂巢材料相互比較，以評估圓形蜂巢材料微結構之力學效能，結果證實圓形蜂巢材料具高勁度、高強度及高抗潛變能力之特性，實為一深具開發潛力之新型營建材料。

When cellular materials including regular hexagonal honeycombs and open-cell foams are loaded at elevated temperatures, creep-rupturing and creep-buckling are two possible dominant failure mechanisms. At first, the creep-rupturing of cellular materials subjected to uniaxial tension is analyzed theoretically and found to be described well by the Monkman-Grant relationship. Meanwhile, the Monkman-Grant parameters of cellular materials depend on their microstructure and those of solid cell edges. Moreover, the effects of dual microstructural imperfections of curved cell edges and Plateau borders on the creep-rupturing of regular hexagonal honeycombs are more drastic than those of any single imperfection. Next, the theoretical expressions for describing the creep-buckling times of cellular materials subjected to uniaxial compression are derived. Analytical results indicate that the creep-buckling of cellular materials depend on their relative density and the creep parameters of solid cell edges. Also, the transition of failure mechanism from creep-buckling to creep-rupturing is discussed. Then, the proposed theoretical expressions for creep-rupturing and creep-buckling are compared with the existing experimental results to verify their accuracy and validity. The creep-rupturing and creep-buckling of cellular materials are found to be sensitive to their microstructural imperfections. Subsequently, the stiffness, strength, elastic buckling and creep-rupturing of a two-dimensional cellular material without any microstructural imperfection, circular cell honeycomb, are analyzed theoretically and numerically and compared to those of hexagonal honeycombs to evaluate the efficiency of their microstructure. It is confirmed that circular cell honeycombs used as load-bearing materials are more promising and thus preferred when higher specific stiffness, strength and creep-resistant are sought.

Abstract...………...…………….……………………………………….……...…………...I
Acknowledgements……………………………………………………………………....III
Table of Contents...……………………………………………………………………....IV
List of Tables…..……...……….……………………………………………………..….VII
List of Figures…………...…….………………………………………………...……...VIII
Chapter 1  Introduction ……...….………………………………………………...…….1
1  Literature review...…...……..…….…………………….…………………………3
2  Scope of this thesis...……..………...….………….………………………………6
Chapter 2  Creep-Rupturing of Regular Hexagonal Honeycombs
With Dual Imperfections………………………………………….…...........9
1  Cell Geometry……….…....…………………...……………………….…………9  
2  Theoretical Analysis…………...……………………………………….………..11 
3  Results and Discussion………….……...…....…….…..………………………..17
3.1  Elastic Properties……………………………………………………….18
3.2  Monkman-Grant Parameters……………………………………………19
3.3  Effects of Microstructural Imperfections……………………………….21
4  Summary……………………………………………………………..………….23
Chapter 3  Creep-Buckling of Regular Hexagonal Honeycombs
With Dual Imperfections………………………………………….……….30    
1  Theoretical Analysis……....…………………...……………………….………..30  
2  Results and Discussion ………….…………………………………….………..35
2.1  Elastic Buckling Strength………………………………………………35
2.2  Effect of Dual Imperfections on Creep-Buckling………………………37
2.3  Transition from Creep-Buckling to Creep-Bending……………………41
3  Summary…………………………………………….…..……………………....43
Chapter 4  Creep-Rupturing of Open-cell Foams…………………………………....53    
1  Cell Geometry…………....…………………...……………………….………..53  
2  Theoretical Analysis……………………………………….……………………54 
3  Results and Discussion…....…....…….…..……………………..........................58
3.1  Elastic Properties……………………………………………………….59
3.2  Existing Experimental Results………………………………………….60
3.3  Comparison between Experimental Results and Theoretical Model…...61
4  Summary………………………………...….….….…………………………….65
Chapter 5  Creep-Buckling of Open-Cell Foams………….………………………….72    
1  Theoretical Analysis……………………………………….……………………72
2  Results and Discussion…....…....…….…..……………………..........................77
2.1  Elastic Buckling Strength…………...………………………………….77
2.2  Creep-Buckling……………...………………………………………….78
2.3  Relation between Failure Time and Creep Strain Rate………………....81
2.4  Transition from Creep-Buckling to Creep-Rupturing………………….82
3  Summary………………………………...….….….…………………………….84
Chapter 6  In-Plane Elastic Moduli and Strengths of 
Circular Cell Honeycombs………………………………………...……....92
1  Cell Geometry...……..…….…………………….………………………………93
2  Theoretical Analysis...……...….………….……………………………………..93
2.1  Elastic Modulus…………………………………………………………93
2.2  Poisson’s Ratio………………………………………………………...101
2.3  Brittle Crushing Strength………………………………………………103
2.4  Plastic Yielding Strength………………………………………………105
3  Finite Element Analysis………………………………………………………..107
4  Results and Discussion…………………………………………………………109
4.1  Elastic Modulus………………………………………………………..109
4.2  Poisson’s Ratio………………………………………………………...111
4.3  Brittle Crushing Strength………………………………………………112
4.4  Plastic Yielding Strength………………………………………………113
5  Summary……………………………………………………………………….115
Chapter 7  Creep-Rupturing of Circular Cell Honeycombs……………….….........128
1  Theoretical Analysis…………...……………………………………….………128
2  Results and Discussion………….……...…....…….…..………………………137
3  Summary……………………………………….………………………………141
Chapter 8  Elastic-Buckling of Circular Cell Honeycombs……….……….….........145
1  Numerical Analysis…………...……………………………………….………145
2  Results and Discussion………….……...…....…….…..………………………146
3  Summary……………………………………….………………………………147
Chapter 9  Conclusions and Suggestions…………………...……………….….........151
1  Conclusions……….…………...……………………………………….………151
2  Suggestions…………..………….……...…....…….…..………………………156
Reference………………………………………………………………………………..158
                                    

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校外：2008-07-17公開

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