• Magazine of the Korea Concrete Institute
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• v.3 no.4
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• pp.97-106
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• 1991

The object of this study is to propose the Flexural moment-curvature relationship based on the bond property between concrete and steel for noncracking zone, to evaluate the flexural displacement of reinforced concrete member. The bond-slip relationship and the strain hardening effect of steel were taken into consideration in order to evaluate the spacing of the cracks and the curvature distribution. Calculated curvature distribution along the longitudinal axis was transformed into equivalent curvature distribution. The flexural displacement was calculated by means of double integrals of the equivalent curvature. Furthermore, 34 beams were tested in order to verify the proposed procedure Calculated values agreed well with the experimental data, and so it is pointed out that proposed method is widely acceptable for the practical evaluation of flexural displacement of reinforced concrete member.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.90-98
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• 1997

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of friction pressure on bonding strength and a charicteristic of fracture. The tensile strength of the friction welded joint was increased up to 90% of the Cu base metal under the condition of friction time 1.2 sec, friction pressure 4.5kgf/$\textrm{mm}^2$ and upset pressure 10kgf/$\textrm{mm}^2$. From the results of fracture surface analysis, the increase of friction pressure could remarkably decrease the force and the time to be normally acted on weld interface. The W particles which were included in the plastic zone of Cu side could induce fracture adjacent to the weld interface because their existance in Cu induces a decrease in available section area and an increase in notch effect. Therefore, the tensile strength was decreased at high friction pressure (6kgf/$\textrm{mm}^2$) because the destruction of W was increased by an increase in mechanical force and crack was formed at weld interface.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2033-2042
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• 1993

In conventional SCC susceptibility test, there are constant strain test, constant load test, slow strain rate test(SSRT) and K$_{ISCC}$ test. Among them, the SSRT method is much more aggressive in producing SCC than the other tests, so that the test time of it is considerably reduced. But this SSRT method has mostly been worked using the uniaxial tensile specimen untill now. Therefore, the SSRT method using the tensile specimen(Ten-SSRT) has much difficulty in SCC susceptibility evaluation of a localized region like weldment and the advantage material of high order. Recentely, the small punch(SP) test method using miniaturized small specimen is the very effective test method for fracture strength evaluation of a localized region like weldment and fusion reactor wall irradiated in the nuclear power plant. This paper investigated the possibility of SCC susceptibility evaluation by the SP-SSRT method using the miniaturized small specimen. Therefore, we obtained the result that the SP-SSRT had the possibility for the evaluations of SCC susceptibility for shorter time to corrosive environment compare to Ten-SSRT which was conventional method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.19-27
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• 1992

An enhanced version of the Roufaiel and Meyer model is developed for the simulation of the hysteretic response of reinforced concrete members. This model takes into account the finite size of plastic regions and considers the effects of stiffness degradation, strength deterioration, shear and axial force. A significant improvement is the way in which strength deterioration is simulated during inelastic cyclic loadings. The accuracy of this model has been demonstrated by analytically reproducing numerous laboratory experimental load-deformation curves.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.4
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• pp.278-284
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• 1997

EMAT는 비접촉으로 초음파를 송수신 할 수 있는 탐촉자로서 시험체와 탐촉자간의 접촉을 위한 매개 물질이 필요치 않으므로, 움직이고 있는 물체에 초음파탐상법을 적용하고자 하는 분야와 초음파의 속도를 정밀하게 측정하고자 하는 분야에 주로 응용된다. 구체적으로는 길이가 긴 튜브류의 결함 탐상, 용접중인 재료의 용접상태 감시, 기차바퀴 및 레일의 결함 탐상, 고온상태인 재료의 결함 탐상 등이 비접촉 특성을 이용하여 적용될 수 있는 분야이며, 재료의 집합조직 및 소성이방성의 측정, 재료의 미세조직 및 기계적 강도의 예측, 그리고 잔류응력의 측정 등이 정밀한 초음파속도 및 감쇠의 측정으로부터 적용될 수 있는 분야이다. EMAT가 일반적인 접촉식초음파탐상법에 비하여 특별한 분야에의 응용에 큰 장점을 가지고 있지만, 낮은 에너지 전환효율, 넓은 불감영역, 그리고 사용주파수의 한계 등의 문제를 가지고 있기 때문에 기존의 접촉식 방법의 적용이 용이한 분야에의 적용은 필요하지 않다. 그러나 특별한 목적과 용도에의 적용 필요성이 생길 경우에는 적절한 연구를 통하여 알맞은 탐촉자를 제작하고 탐상 방법을 개발함으로서 본래의 목적에 알맞은 탐상이 수행될 수 있다.

• Journal of the Korean Chemical Society
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• v.40 no.10
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• pp.656-662
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• 1996

Using low temperature and atmospheric pressure method, we synthesized Na, TPA-ZSM-5 with Si/Al ratio of about 100. We employed 27Al and 29Si MAS NMR spectroscopy and FT-IR to investigate the crystallization process as a function of time. The chemical shift depends on the initial composition of reactants and changes during the course of synthesis different from those reported by others earlier. However, the chemical shift of our final product showed in the range of typical ZSM-5. And the defect site was removed by the calcine. From XRD and SEM data, the formation of ZSM-5 was also confirmed.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.180-189
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• 1994

An approximate method of normal coordinate idealization for use in nonlinear R /C frames has been developed. Normal coordinate apporaches have been used for nonlinear problems in the past, but they are not recerved wide acceptance because of the need for eigenvector computation in each time step. The proposed method circumvents the eigenvector recalculation problem by evaluating a limited number of sets of mode shapes in performing the dynamic analysis. Then some of the predetermined sets of eigenvectors are used in the nonlinear dynamic repeatedly. The method is applied to frame structures with ductile R /C elements. The plastic hinge zones are modeled with hysteres~s loops which evince degrading stiffness and pinching effects. Effxiencies and accuracies of the method for this application are presented.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.277-286
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• 2003

A constitutive equation was implemented in order to model the behavior in overall ranges from small to large strains, which is based on anisotropic hardening rule and total stress concept. The constitutive model was implemented in ABAQUS code in which large deformation analysis can be performed accurately and efficiently. The formulation includes (1) finite strain plasticity on the basis of Jaumann stress rate, (2) implicit stress integration and (3) consistent tangent moduli. A large deformation analysis was performed with the constitutive model using ABAQUS program. In the analysis of an actual embankment, it was found that the proposed model was formulated accurately and efficiently.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.107-112
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• 2002

Basically, ship structure consists of the plate members, and a strength of overall ship structurnds on the stiffness and strength of ship platings. If buckling which causes to deflect ship plate members occurs, the stiffness of ship plate markedly decreases, and thus buckling has a serious effect on the stiffness or strength of overall ship structure. Buckling is one of the most important design criteria when we scantle structure members. In the present study, a inplane rigidity of a compressed ship plate above buckling load is proposed. The proposed inplane rigidity is available in the elastic or elasto-Plastic ranges in order to can out a more efficient and reliable design.

• Korean Journal of Computational Design and Engineering
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• v.12 no.4
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• pp.255-262
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• 2007

In the finite element analysis of forming process, objects are described with a finite number of elements and nodes and the approximated solutions can be obtained by the variational principle. One of the shortcomings of a finite element analysis is that the structure of mesh has become inefficient and unusable because discretization error increases as deformation proceeds due to severe distortion of elements. If the state of current mesh satisfies a certain remeshing criterion, analysis is stopped instantly and resumed with a reconstructed mesh. In the study, a new remeshing algorithm using tetrahedral elements has been developed, which is adapted to the desired mesh density. In order to reduce the discretization error, desired mesh sizes in each lesion of the workpiece are calculated using the Zinkiewicz and Zhu's a-posteriori error estimation scheme. The pre-constructed mesh is constructed based on the modified point insertion technique which is adapted to the density function. The object domain is divided into uniformly-sized sub-domains and the numbers of nodes in each sub-domain are redistributed, respectively. After finishing the redistribution process of nodes, a tetrahedral mesh is reconstructed with the redistributed nodes, which is adapted to the density map and resulting in good mesh quality. A goodness and adaptability of the constructed mesh is verified with a testing measure. The proposed remeshing technique is applied to the finite element analyses of forging processes.