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임원균,최승룡,Lim, Won-Kyun,Choi, Seung-Yong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.6
The objective of this work is to develop the capability to analyze accurately the mixed-mode propagation of a crack in composite structures with elastic orthotropic material stiffness properties and anisotropic material strength characteristics. In order to develop the capability to fully analyze fracture growth and failure in anisotropic structures, we examined the fundamental problem of mixed mode fracture by carrying out the analysis on orthotropic materials with an inclined crack subject to biaxial loading. Our goal here is to include an additional term in the asymptotic expansion of the crack tip stress field and to show that the direction of crack initiation can be significantly affected by that term. We employ the normal stress ratio theory to predict the direction of crack extension. It is shown that the angle of crack extension can be altered by horizontal loads and the use of second order term in the series expansion is important f3r the accurate determination of crack growth direction.
임원균(Won-Kyun Lim),조형석(Hyoung-Seok Cho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The problem of predicting the fracture strength behavior in orthotropic plate with a erack inclined with respespect to the principal material axes is analyzed. Both the load to cause fracture and the erack direction of crack growth are of interest. The theoretical results based on the normal stress ration theory show significant effects of biaxial loading and the fiber orientation on 솜 erack growth angle and the critical stress. The additional term in the asymptotie expansion of the crack tip stress field appears to provide more accurate critical streeprediction.
임원균(Won-Kyun Lim),조형석(Hyoung-Seok Cho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
The problem of an orthotropic material with a central crack is studied. The material is subjected to uniform biaxial loading along its boundary. The normal stress ratio theory is applicd to predict fracture strength behavior in cracked orthotropic matcrial. The dependence of the critical stress with respect to the biaxial loading and the crack orientation is discussed. our analysis shows significant effects of biaxial loading on the critical stress. The additional term in the asymptotic expansion of the crack tip stress ficld appcars to provide more accurate critical stress prediction.
임원균,정우길,Lim, Won-Kyun,Jeong, Woo-Kil 한국전산구조공학회 2011 한국전산구조공학회논문집 Vol.24 No.1
본 논문에서는 Tsai-Hill기준을 변형하여 조합하중을 받는 이방성재료의 강도를 정확히 예측할 수 있는 새로운 파손기준을 제안하였다. 이 기준의 유효성은 조합하중을 받고 있는 Kraft 판지에 대한 실험결과와 비교하여 나타내었다. 재료축 방향의 전단응력이 주어진 경우, Tsai-Hill기준은 매우 보수적인 결과를 보여주고 있으나, 본 해석에서 제안한 기준은 실험 결과와 잘 일치하고 있다. 또한 Tan-Cheng기준과 비교하여 강도를 더욱 단순하게 해석할 수 있는 능력을 갖고 있다. Based on the form of the Tsai-Hill criterion, a new failure criterion for anisotropic material subjected to combined stress is developed and demonstrated. It is capable of accurately calculating the strength of anisotropic materials. The generality and accuracy of the present failure criterion are illustrated by examination through the use of Kraft paperboards under various loading conditions. Compared to the Tsai-Hill theory, which is much too conservative at high levels of shear stress, the present criterion has a good agreement with the experimental data. It also has the ability to calculate the strength more simply, compared to the Tan-Cheng theory.