利用微極彈性理論分析蜂巢式結構之波桑比效應; Analysis of the effect of Poisson's ratio for the honeycomb structure using the micropolar elasticity theory

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题名:	利用微極彈性理論分析蜂巢式結構之波桑比效應;Analysis of the effect of Poisson's ratio for the honeycomb structure using the micropolar elasticity theory
作者:	楊德威;Der-Uei Yang
贡献者:	機械工程研究所
关键词:	微極彈性理論;有限元素法;蜂巢式結構;波桑比;Poisson's ratio;honeycomb structure;finite element method;micropolar elasticity theory
日期:	2002-06-06
上传时间:	2009-09-21 11:32:37 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本文以微極彈性理論為基礎，利用平面線性三角形元素，推導出二維微極彈性理論之有限元素方程式，並依此撰寫相關之Fortran程式，作為數值分析之工具。首先以微極彈性方形板為例，假設其受到軸向的均佈負荷作用，計算方形板的應力應變值以驗證本程式之收斂性與精確性。藉由微極材料常數與微極彈性常數之改變，來分析受力變形後微極彈性方形板其波桑比與微極材料常數或微極彈性常數之間的相互關係。其次分析受力變形後微極彈性蜂巢式結構波桑比值的變化。藉由不同的結構肋寬、肋長與內凹角度等幾何參數，以探討結構幾何參數改變與受力變形後內凹型蜂巢式結構波桑比之間的相互關係。除此之外，改變微極材料常數如微極楊氏模數、微極波桑比、特徵長度與力偶因子N，或在微極彈性限制條件下改變、、與等四個微極彈性常數，可以得到對受力變形後內凹型蜂巢式結構波桑比值之影響。經由本文的研究結果可以發現，雖然微極彈性材料本身固有之波桑比均為正值，但由微極彈性材料所組成之內凹型蜂巢式結構，若在適當的內凹角度、結構肋寬與肋長等幾何條件下，藉由微極材料常數或微極彈性常數的改變，此結構受力變形後可具有可觀的負波桑比值。但是對受力變形後之微極彈性方形板而言，微極常數改變幾乎不會造成其波桑比值的變化。 A two-dimensional triangular finite element formulation including extra degree of freedom was derived on the basis of the Eringen's micropolar elasticity theory using linear triangular element and a corresponding computer program was also developed. Firstly, we investigate the relation between the Poisson’s ratio of a deformed micropolar elastic rectangular plate by changing the micropolar material constants and the micropolar elastic constants. Secondly, we analyze the variation of the structural Poisson’s ratio for a deformed micropolar elastic honeycomb structure. By varying the structural cell rib width and length, the re-entrant angle of the honeycomb structure, the micropolar material constants and the micropolar elastic constants in accordance with the micropolar elastic restrictions, we can obtain the effects on the structural Poisson’s ratio of a deformed re-entrant honeycomb structure. According to our numerical results, with appropriate re-entrant angle, cell rib length and width of the honeycomb structure, by changing the micropolar material and elastic constants, the honeycomb structure after normal distributed loading can exhibit amazing negative Poisson’s ratio. But for the deformed micropolar elastic rectangular plate, the variation of the micropolar constants can not alter the corresponding Poisson’s ratio.
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