유한요소법에 의한 이방성재료내 균열의 응력확대계수 결정 ( Determination of Stress Intensity Factor for the Crack in Anisotropic Solids Using the Finite Element Method )

임원균,진영균,강석진 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2 No.1

2次元 彈性 균열問題에의 境界要素法의 適用

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.

비특이항을 고려한 균질이방성체내 수평균열의 해석

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.

평판내 링압인에 의한 피로균열의 성장거동

임원균,송정훈 明知大學校 産業技術硏究所 2002 産業技術硏究所論文集 Vol.21 No.-

A method for the retardation of fatigue crack growth using ring indentation at the vicinity of a crack is examined. Residual stresses near crack tip are evaluated suing gracture mechanics approach. The motivation is to develop a simple and effective method for obtaining an increase in fatigue lives to total failure of materials with crack. Fatigue testing of aluminum specimen showed that the retardation effects are observed after the application of the method.

Fisetin-Rich Extracts of Rhus verniciflua Stokes Improve Blood Flow Rates in Mice Fed Both Normal and High-Fat Diets

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.

조합하중을 받는 Kraft 판지의 강도예측

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.

境界要素法을 利用한 應力擴大係數 K₁의 解析

임원균 明知大學校 産業技術硏究所 1985 産業技術硏究所論文集 Vol.4 No.-

Two prominent numerical methods which are used to perform the elastic stress analysis are the finite element method (FEM) and the boundary element method (BEM). The FEM has been successfully used for elastic stress analysis and subsequent determination of the stress intensity factor. The BEM has also been successfully applied for elastic stress analysis. The man disadvantage of the FEM is that a domain discretization is required to perform the analysis. The BEM is based on a mathematical formulation which reduces the dimensionality of a problem by relating surface tractions to surface displacements. The solution of boundary equation reduces the problems dimensionality by one. Because of the reduction of dimension of the problem, the size of the algebraic problem is considerably smaller than for finite element modes. The BEM involves discretization only of the boundary of the structure and the governing differential equation is solved exactly in the interior, leading to greater accuracy. The paper investigates the utility of BEM to fracture mechanics. The paper also presents the comparisions of BEM and FEM for SIF computation of a two dimensional crack problem. Two methods for calculating the SIF, stress method and total energy method are used. Models for analysis are two dimensional elastic body with through crack under plane strain

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.

유한요소법에 의한 이종재료 접합면에 수직인 균열의 응력확대계수 결정

임원균,김상철,이창수 대한기계학회 1993 대한기계학회논문집 Vol.17 No.10

Abdi's numerical method(ref.13) for representing a stress singularity by shifting the mid-side nodes of isoparametric elements is reviewed. A simple technique to obtain the optimal position of the mid-side nodes in quadratic isoparametric finite element is presented. From this technique we can directly obtain the position of the side-nodes adjacent to the crack tip. It is also observed that the present technique provides good accuracy for the expression of the opening displacement and the determination of the mid-side nodes for more wide range of material properties than that obtained by Abdicant the finite element method is applied to determine stress intensity factors for pressurized crack perpendicular to and terminating at the interface of two bonded dissimilar materials. A proper definition for stress intensity factors of a crack perpendicular to bimaterial interface is provided. It is based upon a near-tip displacement solutions on the crack surface for interface crack between two dissimilar materials. Numerical testing is carried out with the eight-node and six-node elements. The results obtained are compared with the previous solutions.