• Title/Summary/Keyword: 재료 이방성

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Computer simulation of the effects of anisotropic grain boundary energy on grain growth in 2-D (이방성 결정립 계면에너지의 2차원 결정립 성장에 미치는 효과에 대한 컴퓨터 모사)

  • Kim, Shin-Woo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.22 no.4
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    • pp.178-182
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    • 2012
  • The grain growth is very important because of its great influence on the various materials properties. Therefore, in this study, the effects of anisotropic grain boundary energy on grain growth in 2-D have been investigated with a large scale phase field simulation model on PC. A $2000{\times}2000$ grid system and the initial number of grains of about 73,000 were used in the computer simulation. The anisotropic ratio of grain boundary energy, ${\sigma}_{max}/{\sigma}_{min}$, has been varied from 1 to 3. As the anisotropy increased, the grain growth exponent, n, increased from 2.05 to 2.37. The grain size distribution showed a central plateau in the isotropic case, and was changed into no central plateau and the increasing population of very small grains in the anisotropic case, resulting from slowly disappearing grains. Finally, simulated microstructures were compared according to anisotropy.

A Practical Method of Acoustic Emission Source Location in Anisotropic Composite Laminates (이방성 적층복합재 구조에서 AE 발생원 위치표정을 위한 실용적인 방법)

  • Kim, Jeong-Kon;Kang, Yong-Kyu;Kwon, Oh-Yang
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.3
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    • pp.237-245
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    • 2003
  • Since the velocity is dependent on the fiber orientation in anisotropic composites, the application of traditional acoustic emission (AE) source location techniques based on the constant velocity to composite structures has been practically impossible. The anisotropy makes the source location procedure complicated and deteriorates the accuracy of the location. In this study, we have divided the region of interest(ROI) into a set of finite elements, taken each element as a virtual source, and calculated the arrival time differences between sensors by using the velocities at every degree from 0 to 90. The calculated and the experimentally measured values of the arrival time difference aye then compared to minimize the location error. The results from two different materials, namely AA6061-T6 and CFRP(uni-directional; UD, $[0]_{32}4$) laminate confirmed the practical usefulness of the proposed method.

In-plane Stress Analysis of Relating Composite Disks (복합재료 회전원판의 면내응력 해석)

  • Koo Kyo-Nam
    • Composites Research
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    • v.18 no.4
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    • pp.8-13
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    • 2005
  • Rotating circular disks are widely used in data storage devices as well as in traditional industrial machines. Faster rotating speed is required in data storage devices for higher data transfer rate. In this Paper an application of composite materials to CD is proposed to increase critical speeds and the strength analysis was performed. A differential equation of displacement is derived for the analytic stress distribution of rotating polar orthotropic disk. The stress distributions for typical GFRP and CFRP disks and the maximum allowable speeds subjected to a constraint of tensile strength are presented in addition to polycarbonate disk. The results show that the application of CFRP to rotating disk can increase the maximum allowable rotating speed but this may not be applicable to GFRP disk.

Deformation Behaviors around Tunnel in Anisotropic Rocks Considering Joint Orientation and Rock Pressure Condition Using Scaled Model Tests (이방성 암반의 방향성과 측압조건을 고려한 터널 모형실험 연구)

  • Jung, Hyung-Rae;Kim, Jong-Woo
    • Tunnel and Underground Space
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    • v.16 no.4 s.63
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    • pp.313-325
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    • 2006
  • In this study, scaled model tests were performed to investigate the deformation behaviors around tunnels located in anisotropic rocks. Fifteen types of test models which had respectively different joint angles and rock pressure conditions were made, where the modelling materials were the mixture of sand, plaster and water. All of the tested models showed the shear failure mechanism at the stress-concentrated regions and sliding phenomena according to the joint planes. The direction of joint inclination turned out to have great effect on the tunnel deformation behaviors. The models of joint inclination less than $30^{\circ}$ showed considerable floor heavings. The model of $50^{\circ}$ joint inclination showed the least tunnel convergence among the tested models regardless of rock pressure condition, so that it was thought as the most stable model. Furthermore, the failure mechanisms and deformation behaviors of tunnel models were strongly dependent on the coefficient of rock pressure.

Numerical Analysis of the Electro-discharge Machining Process of a Conductive Anisotropic Composite (전기전도성 이방성 복합재료 방전가공의 수치 해석)

  • Ahn, Young-Cheol;Chun, Kap-Jae
    • Korean Chemical Engineering Research
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    • v.47 no.1
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    • pp.72-78
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    • 2009
  • For the electro-discharge machining of an electro-conductive anisotropic composite, an unsteady state formulation was established and solved by Galerkin's finite element method. The distribution of temperature on work piece, the shape of the crater and the material removal rate were obtained in terms of the process parameters. The $12{\times}12$ irregular mesh that was chosen as the optimum in the previous analysis was used for computational accuracy and efficiency. A material having the physical properties of alumina/titanium carbide composite was selected and an electricity with power of 51.4 V and current of 7 A was applied, assuming the removal efficiency of 10 % and the thermal anisotropic factors of 2 and 3. As the spark was initiated the workpiece immediately started to melt and the heat affected zone was formed. The moving boundary of the crater was also identified with time. When the radial and axial conductivities were increased separately, the temperature distribution and the shape of the crater were shifted in the radial and axial directions, respectively. The material removal rate was found to be higher when the conductivity was increased in the radial direction rather than in the axial direction.