• Title, Summary, Keyword: Inhomogeneous Materials

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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.

Plasticity of Amorphous Alloys: 2. Inhomogeneous Deformation (비정질 합금의 소성 2: 불균일변형)

  • Park, Kyoung-Won;Lee, Chang-Myeon;Lee, Jae-Chul
    • Korean Journal of Metals and Materials
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    • v.47 no.11
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    • pp.773-785
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    • 2009
  • Studies of a number of Cu-Zr amorphous alloys have demonstrated that those exhibiting greater plastic strain during homogeneous deformation at room temperature show lower global plasticity associated with inhomogeneous deformation in a typical compression test. Using a combination of experiments and molecular dynamics simulations, we clarify this seeming paradox between the homogeneous and inhomogeneous deformation by exploring the microstructural aspects in view of the structural disordering, disorder-induced softening, and shear localization and relate these findings to the global plasticity of bulk amorphous alloys. Additional analyses were conducted to derive a simple structural parameter that allows the prediction of the global plasticity of bulk amorphous alloys.

Simulation of Inhomogeneous Texture through the Thickness Direction during Hot Rolling Deformation in Strip Cast Al-5wt%Mg Alloy (박판 주조된 Al-5 wt%Mg 합금의 열간압연 시 두께방향 불균일 집합조직 시뮬레이션)

  • Song, Young-Sik;Kim, Byoung-Jin;Kim, Hyoung-Wook;Kang, Seok-Bong;Choi, Shi-Hoon
    • Korean Journal of Metals and Materials
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    • v.46 no.3
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    • pp.135-143
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    • 2008
  • The inhomogeneous texture through the thickness direction can be developed during hot rolling deformation in aluminum alloy. In this study, the inhomogeneous texture evolution through the thickness direction during hot rolling deformation in Al-5 wt%Mg alloy produced by a new strip casting technology was measured experimentally. Macrotexture measurement was conducted using X-ray diffractometer. A finite element analysis with ABAQUS/StandardTM and rate sensitive polycrystal model were used to predict the evolution of hot rolling texture. The experimental results of Al-5 wt%Mg alloy were compared with calculated results. The shear texture components tend to be increased at the surface region of the hot-rolled specimen. It is found that triclinic sample symmetry is more accurate assumption for texture analysis and simulation in the surface region of hot-rolled aluminum alloy.

Analysis of Three-Dimensional Cracks in Inhomogeneous Materials Using Fuzzy Theory

  • Lee, Yang-Chang;Lee, Joon-Seong
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.5 no.2
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    • pp.119-123
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    • 2005
  • This paper describes a fuzzy-based system for analyzing the stress intensity factors (SIFs) of three-dimensional (3D) cracks. 3D finite element method(FEM) was used to obtain the SIF for subsurface cracks and surface cracks existing in inhomogeneous materials. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy theory. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. The singular elements such that the mid-point nodes near crack front are shifted at the quarter-points, and these are automatically placed along the 3D crack front. The complete FE model is generated, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. The results were compared with those surface cracks in homogeneous materials. Also, this system is applied to analyze cladding effect of surface cracks in inhomogeneous materials.

Evaluation of Inhomogeneous Deformation and Stress Concentration In Polymer Composites Injection Weld by means of Thermoelastic Techniques

  • Lim, Jae-Kyoo;Kim, Yon-Jig
    • Journal of Mechanical Science and Technology
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    • v.15 no.12
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    • pp.1616-1622
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    • 2001
  • Fiber composite materials are widely used in aerospace industries due to their high specific strength and stiffness. Especially, the increasing use of polymer composite materials for injection of automobile components has led to a considerable interest in the application of stress pattern analysis by thermal emission to these composite materials. Therefore, in this study the microstructure of glass fiber orientation at the parent and weld line of polycarbonate is observed by a light transmission. And we also investigate a stress concentration model of a notch including short glass fibers. Especially the polymer injection weld reorients the fiber to suggest a new method for the evaluation of inhomogeneous deformation.

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Mimicking the pattern formation of fruits and leaves using gel materials

  • Chen, Li;Zhang, Yang;Swaddiwudhipong, Somsak;Liu, Zishun
    • Structural Engineering and Mechanics
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    • v.50 no.5
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    • pp.575-588
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    • 2014
  • Gel materials have recently gained more attention due to its unique capability of large and reversible volumetric changes. This study explores the possibility of mimicking the pattern formation of certain natural fruits during their growing process and leaves during drying processes through the swelling and de-swelling of gel materials. This will hopefully provide certain technical explanations on the morphology of fruits and plants. We adopt the inhomogeneous field gel theory to predict the deformation configurations of gel structures to describe the morphology of natural fruits and plants. The growing processes of apple and capsicum are simulated by imposing appropriate boundary conditions and field loading via varying the chemical potential from their immature to mature stages. The drying processes of three types of leaves with different vein structures are also investigated. The simulations lead to promising results and demonstrate that pattern formation of fruits and plants may be described from mechanical perspective by the behavior of gel materials based on the inhomogeneous field theory.

Evaluation of Homogeneous Ultra-fine Grain Refinements via Equal Channel Angler Pressing Process (등통로각압축공정을 통한 결정립의 균질한 초미세립화에 대한 고찰)

  • Kim, W.;Lee, H.H.;Seo, S.J.;Lee, J.K.;Yoon, T.S.;Kim, H.S.
    • Transactions of Materials Processing
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    • v.27 no.4
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    • pp.222-226
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    • 2018
  • Severe plastic deformation (SPD) is a promising method for drastically enhancing the mechanical properties of the materials by grain refinement of metallic materials. However, inhomogeneous deformation during the SPD process results in the inhomogeneous microstructure of the SPD-processed material. We manufactured cylindrical copper specimens of 42 mm in diameter with ultrafine grains (UFG) using an equal channel angular pressing (ECAP) to figure out the relationship between homogeneous microstructure and the number of the processing passes. Two specimens, which are ECAP-processed 4 times (4pass) and 6 times (6pass) each with Route Bc, are prepared for comparison of mechanical properties and microstructure. The results show that the mechanical properties of the two specimens (4pass and 6pass) are similar. Moreover, both the specimens show highly enhanced mechanical properties. The 4pass specimen, however, shows inhomogeneity in hardness distribution, while the 6pass specimen shows a homogeneous distribution. Microstructure analysis reveals that the 4pass specimen has an inhomogeneous microstructure with incompletely refined grain structure. This inhomogeneity of the 4pass specimen could be explained by the circumferential rotation during ECAP process.

Wave Propagation Analysis in Inhomogeneous Media by Using the Fourier Method

  • Kim, Hyun-Sil;Kim, Jae-Seung;Kang, Hyun-Joo;Kim, Sang-Ryul
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.3E
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    • pp.35-42
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    • 1998
  • Transient acoustic and elastic wave propagation in inhomogeneous media are studied by using the Fourier method. It is known that the fourier method has advantages in memory requirements and computing speed over conventional methods such as FDM and FEM, because the Fourier method needs less grid points for achieving the same accuracy. To verify the proposed numerical scheme, several examples having analytic solutions are considered, where two different semi-infinite media are in contact along a plane boundary. The comparisons of numerical results by the Fourier method and analytic solutions show good agreements. In addition, the fourier method is applied to a layered half-plane, in which an elastic semi-infinite medium is covered by an elastic layer of finite thickness. It is showed how to derive the analytic solutions by using the Cagniard-de Hoop method. The numerical solutions are in excellent agreements with analytic results.

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Inhomogeneous Rolling Texture of Multilayered Aluminum Sheet (다층압연된 알루미늄의 불균질압연집합조직)

  • Choi, Chang-Hee;Hong, Seung-Hyun;Kwon, Jae-Wook;Oh, Kyu-Hwan;Lee, Dong-Nyung
    • Transactions of Materials Processing
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    • v.4 no.4
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    • pp.353-364
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    • 1995
  • An inhomogeneous rolling texture of high purity aluminum has been observed by a multilayered rolling. The shear texture of (100)[110] component developed in the surface layer, and the copper type rolling texture developed in the middle and center layers. The through-thickness texture variation has been calculated by the full-constraint Taylor model combined with FEM. The calculated results are in good agreement with the measured data.

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