• 한국해양공학회지
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• 제20권5호
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• pp.42-48
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• 2006

This paper shows theresults of centrifuge model experiments to investigate the behavior of a replacement method in dredged and reclaimed ground. For this experimental work, centrifuge model tests were carried out to investigate the behavior of a replacement method in soft clay ground. Basic soil property tests were performed to find the mechanical properties of clay soil sampled from the southern coast of Korea, which was used for the ground material in the centrifuge model tests. The reconstituted clay ground of the model was prepared by applying reconsolidntion pressure in a 1 g condition with a specially built model container. Centrifuge model tests were carried out under the artificially accelerated gravitational level of 50 g. Replacement material of lead with a certain degree of angularity was used and placed until the settlement of the replacement material embankment reached a state of equilibrium. Vertical displacement of the replacement material was monitored during tests. The depth and shape of the replacement, especially the slope of the penetrated material and the water content of the clay ground were measured after finishing tests. Model tests for investigating the stability of an embankment after backfilling were also performed to simulate the behavior of a dike treated with replacement and backfilled with sandy material. As a result of the centrifuge model test, the behavior of the replacement, the mechanism of the replacement material being penetrated into clay ground, and the depth of the replacement were evaluated.

• 한국군사과학기술학회지
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• 제25권6호
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• pp.580-585
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• 2022

In this study, the high-temperature dielectric constant of Si₃N₄ ceramics, a representative non-oxide-based radome material, was evaluated and the cause of the dielectric constant change was analyzed in relation to the oxidation behavior. The dielectric constant of Si₃N₄ ceramics was 7.79 at room temperature, and it linearly increased as the temperature increased, showing 8.42 at 1,000 ℃. As results of analyzing the microstructure and phase for the Si₃N₄ ceramics before and after heat-treatment, it was confirmed that oxidation did not occur at all or occurred only on the surface at a very insignificant level below 1,000 ℃. Based on this, it is concluded that the increase in the dielectric constant according to the temperature increase of Si₃N₄ ceramics is irrelevant to the oxidation behavior and is only due to the activation of charge polarization.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2005년도 하계학술연구발표회 논문개요집
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• pp.90-90
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• 2005

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.251-257
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• 1999

Smart structure that contains sensors, which are either embedded in a composite material or attached to a structure, is currently receiving considerable attention. Fiber Bragg grating sensor, one of the optical fiber sensors, has been widely used to sense strain and temperature for smart structures since both parameters change the resonant frequency of the grating. In this paper, according to the various heating and cooling conditions the thermal behavior of unidirectional composite material was monitored by embedding the fiber Bragg grating sensors in the longitudinal and transverse directions of unidirectional composites. The thermal behavior of unidirectional composite material was monitored for various heating and cooling rates and applied pressure. It was found that the thermal behavior was unaffected by pressure variations and heating and cooling rates applied to the composites. The thermal strains were measured by considering the shift in Bragg wavelength that was generated by the thermal expansion of composite specimen. The longitudinal and transverse C.T.E.'s were also obtained from the corresponding temperature-thermal strain curves.

• 대한금속재료학회지
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• 제46권5호
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• pp.276-282
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• 2008

Material degradation of Cr steels in boiler tubes was accompanied by the microstructural changes including carbide behavior and crack formation. The microstructural change and the mechanical behavior of hardness and creep properties in accelerated heat-treatments were studied in order to identify the material degradation of the X20 Cr steel. The degradation behavior was occurred in the hardness increasing followed by decreasing due to carbide dissolution and precipitation.

• Structural Engineering and Mechanics
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• 제69권3호
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• pp.243-255
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• 2019

Utilization of fiber beam-column element has gained considerable attention in recent years due mainly to its ability to model distributed plasticity over the length of the element through a number of integration points. However, the relatively high sensitivity of the method to modeling parameters as well as material behavior models can pose a significant challenge. Residual drift is one of the seismic demands which is highly sensitive to modeling parameters and material behavior models. Permanent deformations play a prominent role in the post-earthquake evaluation of serviceability of bridges affected by a near-fault ground shaking. In this research, the influence of distributed plasticity modeling parameters using both force-based and displacement-based fiber elements in the prediction of internal forces obtained from the nonlinear static analysis is studied. Having chosen suitable type and size of elements and number of integration points, the authors take the next step by investigating the influence of material behavioral model employed for the prediction of permanent deformations in the nonlinear dynamic analysis. The result shows that the choice of element type and size, number of integration points, modification of cyclic concrete behavior model and reloading strain of concrete significantly influence the fidelity of fiber element method for the prediction of permanent deformations.

• Advances in concrete construction
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• 제7권2호
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• pp.65-74
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• 2019

This paper reports on the results of a parametric study, which examines the effects of varying aspect ratios on the dynamic response of cylindrical silos directly supported on the ground under earthquake loading. Previous research has shown that numerical models can provide considerably realistic simulations when it comes to the behavior of silos by using correct boundary conditions, appropriate element types and material models. To this end, a three dimensional numerical model, taking into account the bulk material-silo wall interaction, was produced by the ANSYS commercial program, which is in turn based on the finite element method. The results obtained from the numerical analysis are discussed comparatively in terms of dynamic material pressure, horizontal displacement, equivalent base shear force and equivalent bending moment responses for considered aspect ratios. The effects experienced because of the slenderness of the silo in regards to the seismic response were evaluated along with the effectiveness of the classification system proposed by Eurocode in evaluating the loads on the vertical walls. Results clearly show that slenderness directly affects the seismic response of such structures especially in terms of behavior and the magnitude of the responses. Furthermore the aspect ratio value of 2.0, given as a behavioral changing limit in the technical literature, can be used as a valid limit for seismic behavior.

• 한국주조공학회지
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• 제42권6호
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• pp.347-357
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• 2022

본 연구에서는 주조공장의 장입재 충전 거동을 3차원적으로 시각화하고자 하였다. 장입재와 용해로의 실제 조건을 반영하여 시뮬레이션하였다. 3차원 시각화 시뮬레이션이 제조 현장의 장입재 충전 거동을 사실적으로 잘 구현하는지 확인하였다. 3차원 시각화 시뮬레이션에 의한 현실적인 충전 상태를 이상적인 충전 상태와 비교하였다. 어떤 경우에 두 충전 상태의 차이가 발생하는지 분석하였다. 3차원 시각화 시뮬레이션을 제조 공정에 적용할 경우의 특징을 살펴보았고, 주조 분야에서의 여러 활용 방안을 제안하였다.

• 한국자동차공학회논문집
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• 제18권3호
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• pp.74-79
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• 2010

Automotive industries are interested in material development with low weight and recycling. Grommet is made from EPDM at rubber and used as an automotive component. The nonlinear material properties of rubber are important to predict the behaviors of rubber product. This study concerns material property test to achieve stress-strain curve. Curve fitting is carried out to obtain the nonlinear material constant. The nonlinear material constants of rubber are used for the nonlinear finite element analysis. The results of finite element analysis is executed to predict the behavior property of grommet.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3715-3727
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• 1996

Compression behavior of semi-solid aluminum alloys with controlled solid fractions was investigated in the present study. The stress and strain relationships were obtained from the compression test. Variations of the solid fraction distribution and the material behaviour were investigated for various friction coeffieiants and die speedsd. For a finite element analysis, the semi-solid material was described by a compressible regid viscoplastic model for the solid region and darcy's law for the liquid region. The computed results were compared with experimental data for the validity of the yield criteria.