https://scholars.lib.ntu.edu.tw/handle/123456789/168676
標題: | 塑性之偽歐空間群論與實驗(1/3) A study of plasticity by gruops on pseudo-Euclidean spaces and experiments (1/3) |
作者: | 洪宏基 | 關鍵字: | 塑性;偽黎曼流形;特殊線性群;軸扭雙向循環實驗;收縮比;plasticity;pseudo-Riemann manifold;special pseudo-linear group;axial-torsional cyclic test;contraction ratio | 公開日期: | 2000 | 出版社: | 臺北市:國立臺灣大學土木工程學系暨研究所 | 摘要: | The project employed a group-theoretical ap- proach to investigate constitutive models of elastoplasticity. In the axial-torsional test, the hoop and radial strains are usually not known a priori; hence, in the constitutive model simula- tion of the responses they can not be viewed as inputs. This greatly complicates the constitutive analyses because the resulting differential con- stitutive equations become highly nonlinear. To tackle this diffculty we convert the highly nonlin- ear axial-torsional problem of perfect elastoplas- ticity to a quasi-linear system _X = A(X; t)X, where A(X; t) 2 sl(2; 1;R) is a local Lie algebra of the special pseudo-linear group SL(2; 1;R). The underlying space of this problem is found to be a pseudo-Riemann manifold which is lo- cally pseudo-Euclidean space E3 2;1 with the metric indefinite and also dependent on the time com- ponent. Utilizing the internal symmetry group, we can consequently develop a highly accurate group-preserving scheme, which guarantees the fulfillment of the consistency condition in every time marching of the calculations. The axial-torsional test equipment MTS809 of the NTU College of Engineering and the pressure control machine was used to study the cyclic and ratchetting behavior of tubular specimens of Al- 7075 and stainless steel 316. We also studied contraction ratios experimen- tally, one rate form and one total form under dif- ferent initial values of the specimens. The values of both contraction ratios may be greater than 1=2. Moreover, for some cases we found that the rate form contraction ratio exceeds the value 1. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/2691 | 其他識別: | 892211E002032 | Rights: | 國立臺灣大學土木工程學系暨研究所 |
顯示於: | 土木工程學系 |
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892211E002032.pdf | 602.88 kB | Adobe PDF | 檢視/開啟 |
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