• Title, Summary, Keyword: 비균질재료

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Stress Intensity Factor Analysis for Surface Crack in Inhomogeneous Materials (비균질재료의 표면균열에 대한 응력확대계수 해석)

  • 김준수;이준성
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.816-819
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    • 2002
  • Accurate stress intensity factor analyses and crack growth rate of surface-cracked components in inhomogeneous materials are needed for reliable prediction of their fatigue lift and fracture strengths. This paper describes an automated system for analyzing the stress intensity factors of three-dimensional (3D) cracks in inhomogeneous materials. 3D finite element method (FEM) was used to obtain the stress intensity factor for subsurface cracks and surface cracks existing in inhomogeneous materials. To examine accuracy and efficiency of the present system, the stress intensity factor for a semi-elliptical surface crack in a plate subjected to uniform tension is calculated, and compared with Raju-Newman's solutions. Then the system is applied to analyze cladding effect of subsurface cracks in inhomogeneous materials. The results were compared with those surface cracks in homogeneous materials. It is clearly demonstrated from these analyses that the stress intensity factors for subsurface cracks are less than those of surface cracks.

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Stress Intensity factor Analysis for Three-Dimensional Cracks in Inhomogeneous Materials (비균질재료의 3차원 균열에 대한 응력확대계수 해석)

  • 김준수;이준성
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.4
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    • pp.197-203
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    • 2003
  • Accurate stress intensity factor analyses and crack growth rate of surface -cracked components in inhomogeneous materials are needed fur reliable prediction of their fatigue life and fracture strengths. This paper describes an automated stress intensity factor analysis of three-dimensional (3D) cracks in inhomogeneous materials. 3D finite element method (FEM) was used to obtain the stress intensity factor fur subsurface cracks and surface cracks existing in inhomogeneous materials. To examine accuracy and efficiency of the present system, the stress intensity factor for a semi-elliptical surface crack in a plate subjected to uniform tension is calculated, and compared with Raju-Newman's solutions. Then the system is applied to analyze cladding effect of subsurface cracks in inhomogeneous materials. The results were compared with those surface cracks in homogeneous materials. It is clearly demonstrated from these analyses that the stress intensity factors for subsurface cracks are less than those of surface cracks. Also, this system is applied to analyze cladding effect of surface cracks in inhomogeneous materials.

The Analysis of P-, and SV-Wave Response in the Homogeneous Half-Space Having Alluvial Deposit Arbitrary Shape (임의 형상의 퇴적층을 갖는 균일 반무한 영역내에서 P파와 SV파 응답해석)

  • 권영록;손영호
    • Journal of the Earthquake Engineering Society of Korea
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    • v.5 no.1
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    • pp.1-6
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    • 2001
  • P파와 SV파와 입사할 때 비균질 퇴적층에서의 지진응답을 유한요소법과 경계여소법을 조합하여 해석하였다. 유한요소법을 사용하여 불규칙한 기하형상과 비균질 재료 특성을 모델링하였고, 경계요소법을 사용하여 인위적인 경계로부터 불필요한 파의 반사를 없앨수 있게 반무한 영역을 모델링하였다. 경계요소의 기본해는 반무한 영역문제에서 반드시 고려해야하는 방사조건을 자동적으로 만족시킨다. 따라서 외부영역과 내부영역의 접촉면에서 표면력의 평행조건과 변위의 연속조건을 사용하여 P파와 SV파에 의한 지진응답을 해석하였다.

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Modeling the Heterogeneous Microstructures of Ti-MMCs in Consolidation Process (강화공정에 따른 비균질 티타늄 금속기 복합재료 모델링)

  • Lee Soo-Yeun;Kim Tae-Won
    • Composites Research
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    • v.18 no.3
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    • pp.21-30
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    • 2005
  • Vacuum hot pressing has been used for the development of titanium metal matrix composites using foil-fiber-foil method. Heterogeneous microstructures prior to and following consolidation have been quantified, and the relations to densification behavior investigated. As shown by the results, dramatic variations of the microstructures including equiaxed $\alpha$, transformed $\beta$ and $ Widmanst\ddot{a}tten$ $\alpha$ are obtained during the process according to the fiber distributions. The dependence of microstructures on the consolidation then has been explained in terms of the change in mechanisms such as grain growth and recrystallization that occur with changing levels of inhomogeneity of deformation. Further, micro-mechanics based constitutive model enabling the evolution of density over time together with the evolutions of microstructure to be predicted has been developed. The mode developed is then implemented into finite element scheme so that practical process simulation has been carried out.

Free Vibration Analysis of Thick Plate Subjected to In-plane Force on Inhomogeneous Pasternak Foundation (비균질 Pasternak지반 위에 놓인 면내력을 받는 후판의 진동해석)

  • Lee, Yong Soo;Kim, Il Jung;Oh, Soog Kyoung
    • Journal of Korean Society of Steel Construction
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    • v.15 no.3
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    • pp.291-298
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    • 2003
  • Recently, as the size of buildings structure becomes large increases, their mat area of building structure is supported or by an inhomogeneous foundation. This paper presents a vibration analysis on thick plates subjected to in-plane force is presented in this paper. The rectangular plate is isotropic, homogeneous, and composed of a linearly elastic material. A vibration analysis of the rectangular thick plate iwas done by useing ofarectangular finite element with 8 nodes and 9 nodes. In this study, the foundation was idealized as a Pasternak foundation model. A Pasternak foundation haves a shear layer on Winkler's model, which idealizes the foundation as a vertical spring. In order tTo analysze the vibration of a plate supported on by an inhomogeneous Pasternak foundation, the value of the Winkler foundation parameter of the central and border zones of the plate awere chosen as WFP1 and WFP2. (fFigure 4.). The Winkler foundation parameter of WFP1 and WFP2 is varied from 0 to 10, $10^2$, and $10^3$ and the shear foundation parameters is were 0, 5, and 10. The ratio of the in-plane force to the critical load iwas applied as 0.4 to 0.8

The Problem of Collinear Cracks in a Layered Half-Plane with a Functionally Graded Nonhomogeneous Interfacial Zone (비균질 구배기능 계면영역을 고려한 적층 만무한체의 동일선상 복수균열 해석)

  • Jin, Tae-Eun;Choe, Hyung-Jip;Lee, Kang-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.4
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    • pp.1275-1289
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    • 1996
  • The plane elasticity problem of collinear cracks in a layered medium is investigated. The medium is modeled as bonded structure constituted from a surface layer and a semi-infinite substrate. Along the bond line between the two dissimilar homegeneous constituents, it is assumed that as interfacial zone having the functionally graded, nonhomogeneous elastic modulus exists. The layered medium contains three collinear cracks, one in each constituent material oriented perpendicular to the nominal interfaces. The stiffness matrix formulation is utilized and a set of homogeneous conditions relevant to the given problem is readily satisfied. The proposed mixed boundary value problem is then represented in the form of a system of integral equations with Cauchy-type singular kernels. The stress intensity factors are defined from the crack-tip stress fields possessing the standard square-root singular behavior. The resulting values of stress intensity factors mainly address the interactions among the cracks for various crack sizes and material combinations.

Deformation Characteristics of Earth Dam Raised by Non-Homogeneous Fill Materials (비균질 재료로 숭상(嵩上)한 흙 댐의 변형 특성)

  • 장옥성;이종규
    • Journal of the Korean Geotechnical Society
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    • v.20 no.8
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    • pp.167-180
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    • 2004
  • In this study finite element analysis using hyperbolic model was performed to predict the characteristics of stress-strain behaviour on concrete face earth dam (CFED : a tentative name) raised with coarse-grained materials corresponding to the face slab bedding zone of concrete face rockfill dam (CFRD). The results of finite element analysis were compared with field monitoring data, and the comparison showed a good agreement. And, the analysis results including locus of maximum displacement, maximum stress, stress concentration, and irregular load transfer would be used to devise rational field monitoring schemes for construction management and quality control during construction of CFED.

Reconstruction and Deconvolution of X-Ray Backscatter Data Using Adaptive Filter (적응필터를 이용한 적층 복합재료에서의 역산란 X-Ray 신호처리 및 복원)

  • Kim, Noh-Yu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.6
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    • pp.545-554
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    • 2000
  • Compton X-ray backscatter technique has been used to quantitatively assess the impact damage in quasi-isotropic laminated composites and to obtain a cross-sectional profile of impact-damaged laminated composites from the density variation of the cross section. An adaptive filter is applied to the Compton backscattering data for the reconstruction and noise reduction from many sources including quantum noise, especially when the SNR(signal-to-noise ratio) of the image is relatively low. A nonlinear reconstruction model is also proposed to overcome distortion of the Compton backscatter image due to attenuation effects, beam hardening, and irregular distributions of the fibers and the matrix in composites. Delaminations masked or distorted by the first few delaminations near the front surface are detected and characterized both in width and location, by application of an error minimization algorithm.

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Characteristics of Contaminant Migration through Hardened Liner and Seashore Clay Considering Effective Diffusion (유효확산을 고려한 고화차수층과 해안점성토층을 통한 오염물이동 특성)

  • 장연수;홍경택
    • Journal of the Korean Geotechnical Society
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    • v.17 no.4
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    • pp.49-55
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    • 2001
  • 본 논문에서는 서해안 폐기물 매립지 하부의 점성토와 고화차수재를 재료로 수행된 확산시험 결과와 현장 조건을 적용하여 오염물이동성에 대한 수치해석을 수행하였다. 무기화합물이 하부 차수재와 원지반퇴적층으로 이동되는 일차원 이동 특성을 대상으로 하였으며 일차원 용질이동해석 프로그램 CDFD(convection-dispersion finite difference)를 현장의 비균질한 지층에 이용할 수 있도록 수정하여 적용하였다. 그 결과 원지반점성토를 통한 용질이동 메카니즘에 확산이 기여하는 정도가 50%로 매우 큰 영향을 갖고 있음을 보여주며 원지반 투수계수가 클수록 인공차수층의 필요성이 증대됨을 알 수 있었다.

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