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Asymptotic analysis of a wedge crack in an anisotropic dielectric material
범현규,Do Ryun Lee,Hyun Seok Jang 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11
The asymptotic problem of a conducting crack emanating from the vertex of a wedge in an anisotropic dielectric material under purely electric loading is investigated. The wedge crack in an isotropic material is solved using a conformal mapping technique. The solution of the wedge crack in an anisotropic dielectric material is obtained from that for the transformed isotropic problem after applying a linear transformation method. The electric field intensity factor for the anisotropic wedge crack is obtained in the closed form. The effects of crack and wedge angles as well as anisotropic parameters on the electric field intensity factor are illustrated. The electric field intensity factor is numerically calculated by using the J integral and finite element analysis to validate the exact solution of the electric field intensity factor.
혼합모드 하중하에서 제하 컴플라이언스법에 의한 파괴 인성 측정
심재룡,이영숙,김도형,범현규,강기추,Sim, Jae-Ryong,Lee, Yeong-Suk,Kim, Do-Hyeong,Beom, Hyeon-Gyu,Gang, Gi-Chu 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.1
Experimental procedure to measure fracture toughness (J$_{c}$) under mixed mode loading using CTS(Compact Tension-Shear) specimens is described. It\`s loading angle ranges from 0$^{\circ}$ to 45$^{\circ}$ with interval of 157. The general outline of experimental procedure is similar to that of ASTM E8l3-89 fur mode I fracture. Equations fur determining J-integral is quoted from the authors' previous works. The relation between unloading compliance and physical crack size was calibrated. As an example, fracture toughness of aluminum alloy 2024p-7361 was measured and some reasonable results of J$_{c}$ with various loading angles were obtained.
이보현(Bo Hyun Lee),Song Lin,범현규(Hyeon Gyu Beom) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.6
순수한 전기장 하에서의 뼈와 유사한 재료의 절연파괴에 대하여 연구하였다. 일반적으로 뼈와 유사한 재료는 강한 유전강도를 가지는 층과 약한 유전강도를 가지는 층이 서로 평행하게 엇갈려 있는 형태로 구성되어 있다. 뼈와 유사한 재료의 약한 층을 관통하는 전도채널의 성장은 전기장의 집중이 완화되기 때문에 지연된다. 관형채널의 선단에서 전기장의 분포를 유한요소해석을 통해 구하였다. 뼈와 유사한 재료의 절연강도를 J 적분을 사용하여 계산하였고, 절연강도에 영향을 미치는 인자들을 찾아내었다. J 적분은 약한 층에서의 절연파괴 면적이 증가할 수록 작아짐을 보였다. 또한, 약한 층과 강한 층의 유전율의 비가 절연파괴에 큰 영향을 미치는 것으로 나타났다. The dielectric breakdown of bone-like materials subject to purely electric fields is investigated. In general, these materials consist of some layers with stronger dielectric strength and others with weaker dielectric strength in a parallel staggered pattern. The growth of the conductive channel is impeded during penetration of the weaker layer in the bone-like material because the electric-field concentration is relieved. The electric-field distribution around the head of the tubular channel is obtained from finite element analysis. The dielectric strength of the bone-like material is evaluated using the J integral, and some parameters affecting the dielectric strength are determined. It is shown that the J-integral values are reduced with an increase in the breakdown area in the weaker layer. It is also found that the ratio of the permittivity of the weaker layer to that of the stronger layer can strongly affect the dielectric breakdown.