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임원균 明知大學校 産業技術硏究所 1986 産業技術硏究所論文集 Vol.5 No.-
A general formulation of the boundary element method is presented for the application of straight crack problem in two dimension. Mutidomain technique of modelling the crack by stitching together is adopted, and the traction singular quarter point element representing the accurate √r displacement and 1/√r traction variations at the crack tip is used. Stress intensity factors are determined for center cracked panel and center slant cracked panel, and results compare with the well-known published values. In this paper the author also compare the results and the efficiency with finite element solution.
임원균,최승룡,안현수,Im, Won-Gyun,Choe, Seung-Ryong,An, Hyeon-Su 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.1
The one-parameter singular expression for stresses and displacements near a crack tip has been widely thought to be sufficiently accurate over a reasonable re ion for any geometry and loading conditions. In many cases, however subsequent terms of the series expansion are quantitatively significant, and so we now consider the evaluation of such terms and their effect on the predicted crack growth direction. For this purpose the problem of a cracked orthotropic plate subjected to a biaxial load is analysed. It is assumed that the material is ideal homogeneous anisotropic. BY considering the effect of the load applied parallel to the plane of the crack, the distribution of stresses and displacements at the crack tip is reanalyzed. In order to determine values for the angle of initial crack extension we employ the normal stress ratio criterion.
임원균 명지대학교 산업기술연구소 2001 産業技術硏究所論文集 Vol.20 No.-
2축하중을 받는 이방성균열체에 대하여 해석을 수행하였다. 재료는 균질이방성체라고 가정하였다. 균열선단주위의 응력분포에 대한 급수전개식에서 2차항을 고려하여 응력식을 산출하였으며 이의 2차항은 균열성장각도의 정확한 예측을 위해서 매우 중요함을 보였다. 균열진전각도의 결정을 위해서 수직응력비 이론을 적용하였으며 넓은 범위의 작용하중에 대하여 해석을 수행하였다.
임원균,박현정,이광수,이정훈,김영동,김경희,박상재,홍석만,전성호 한국식품영양과학회 2016 Journal of medicinal food Vol.19 No.2
Although it has been previously reported that Rhus verniciflua Stokes (RVS) possesses in vitro antiinflammatory activity, the precise in vivo mechanisms of RVS extracts and a main active component called fisetin have not been well elucidated. In this study, using newly developed protocols, we prepared urushiol-free but fisetin-enriched RVS extracts and investigated their effects on the vascular immune system. We found that the water-soluble fractions of detoxified RVS with the flavonoid fisetin can inhibit lipopolysaccharide-induced production of nitric oxide (NO) and prostaglandin E2 (PGE2). Furthermore, RVS can reduce inducible nitric oxide synthase and COX2 gene expression levels, which are responsible for NO and PGE2 production, respectively, in RAW264.7 macrophage cells. Because inflammation is linked to the activation of the coagulation system, we hypothesized that RVS and its active component fisetin possess anticoagulatory activities. As expected, we found that both RVS and fisetin could inhibit the coagulation of human peripheral blood cells. Moreover, in vivo RVS treatment could return the retarded blood flow elicited by a high-fat diet (HFD) back to the normal level in mice. In addition, RVS treatment has significantly reduced body weight gained by HFD in mice. Taken together, the fisetin-rich RVS extracts have potential antiplatelet and antiobesity activities and could be used as a functional food ingredient to improve blood circulation.
임원균 대한안전경영과학회 2001 대한안전경영과학회 학술대회논문집 Vol.2001 No.05
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. 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 the use of second order term in the series expansion is important for the accurate determination of crack growth direction.
서로 다른 두 재료의 접합면에 수직인 균열의 경계요소 해석
임원균,이현규 한국전산구조공학회 1996 한국전산구조공학회논문집 Vol.9 No.1
서로 다른 두 재료의 접합면에 균열이 수직으로 위치하고 있을 때, 균열에서의 응력특이성차수는 두 재료의 재료특성치에 따라서 변화하게 된다. 이와 같은 균열문제를 해석하기 위하여 다영역경계요소법을 사용하였다. 균열을 포함하는 등매개 경계요소 중간절점의 위치를 적절히 이동하여 놓음으로써 변위에 대한 정확한 형상함수를 나타내었으며, 아울러 트랙션에 대해서도 정확한 보간차수를 나타내도록 시도하였다. 3절점 경계요소를 이용하여 수치해석을 수행하였으며, 이의 결과를 기존의 해석결과와 비교 검토하였다. In the particular situations where the crack is terminated at an interface of two materials, the order of stress singularity depends on the elastic constants which specify the properties of two materials. A multidomain boundary element technique is used to solve a crack normal to bimaterial interface. A correct order of shape function is used for displacement by using the isoparametric elements by shifting adequately the side nodes adjacent to this crack tip. A shape function containing the same order of singularity as that in the interface crack is also used for the interpolation of traction. Numerical testing of a binaterial with a crack normal to the interface is carried out with three-node elements. The results obtained are compared with the previous solutions.
3차 등매개 유한요소를 이용한 이종재료 접합면에 수직인 균열의 응력확대계수 평가
임원균,정규철,송치훈,Lim, Won-Gyun,Jeong, Gyu-Cheol,Song, Chi-Hun 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1
When a crack meets bimaterial interface stress singularity depends on the elastic constants of the adjacent materials. In the present study we are going to describe the finite element formulation for problems with a crack to be embedded in the stiffer material$({\mu}_2/{\mu}_1)$. The cubic isoparametric singular element, represented by adequately shifting the mid-side nodes adjacent to the crack tip is constructed to enclose the crack tip. An alternative method to obtain the optimal position of the mid-side nodes of cubic isoparametric elements is presented. In addition, a proper definition for the stress intensity factors of a crack normal to bimaterial interface is provided. It is based upon near a tip displacement solutions. Models for numerical analysis are two dimensional elastic bodies with a through crack under plain strain. The results obtained are compared with the previous solutions.
유한요소법에 의한 직방성재료 내 균열의 응력확대계수 결정
임원균,조형석,강석진,이성근 한국전산구조공학회 2004 한국전산구조공학회논문집 Vol.17 No.1
The stress intensity factors have been widely used in numerical studies of crack growth direction. However in many cases, omissive terms of the series expansion are quantitatively significant, so we consider the computation of such terms. For this purpose, we used the finite element method with isoparametric quadratic quarter-point elements. For examples, infinite square plate with a slant crack subjected to a uniaxial load is analyzed. The numerical analysis were performed for the wide range of crack tip element lengths and inclined angles. The numerical results obtained are compared with the theoretical solutions. Also they were accurate and efficient. 응력확대계수는 균열진전경로의 수치해석적 연구에서 널리 사용되고 있다. 그러나 많은 경우에서 균열선단주위 응력의 급수전개식 중 이어지는 항은 정량적으로 중요하다. 따라서 본 연구에서는 이의 항을 계산하기 위하여 등매개2차특이요소를 이용한 유한요소해석을 수행하였다. 일례로 단축하중을 받는 무한 직방성체 내 경사균열에 대하여 균열요소크기와 균열경사각을 달리 주어 가며 해석을 수행하였으며, 수치해석결과는 이론해와 비교하여 잘 일치하고 있다.