• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.36-43
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• 2006

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.39-44
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• 2011

Plastic gradient from geometrically necessary dislocation(GND) can strongly affect micro-scale plastic behavior of polycrystalline solids. In this research, mechanical behavior of polycrystalline solid is investigated using the finite element method incorporating plastic gradient from GND effect. Gradient hardness coefficient and material length parameter are used to evaluate the effect of the plastic gradient on the behavior of materials. Sensitivity of the modeling parameters on the plastic gradient from GND is presented and effects of plastic gradient and material parameters on the behavior of single crystal inside a polycrystalline aggregate are investigated. It is confirmed that the plastic gradient from GND amplifies hardening response of polycrystals and affects single crystal behavior embedded in polycrystalline solids.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.133-138
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• 2003

As concrete structures are heated, thermal strain can be developed. Because of the boundary conditions, the thermal stress may be arisen. Thermal strain and temperature were measured simultaneously using an optical fiber sensor. Fiber Bragg Grating Sensor(FBG sensor) was used in the measurement. Because it can measure the strains more than two points with one line, it was possible to measure both thermal strain and temperature with one line. To compare data measured by FBG sensor, strain and temperature were measured using strain gauge and thermocouple. The FBG sensor could measure the strain under the temperature greater than $60^{\circ}C$ but strain gauge couldn't. Both the FBG temperature sensor and thermocouple could measure the temperature and the results are related each other linearly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.177-188
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• 1991

The littoral drift in the nearshore zone occurs mainly due to wave action and nearshore currents. Beach topotraphical evolution model presented in this study shows the possibility which can be applied to the prediction of beach deformation over short time interval, associated with the construction of coastal structures. The 3-dimensional beach evolution model, based on Watanabe's equation and Deguchi's flux model, is developed and consists of three submodels of wave transformation, rip-currents, and beach deformation. This model is applied to the several cases with different conditions and compared with the results of Watanabe's numerical model. In addition, the effects of parameters involved are discussed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.495-507
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• 2023

Considering the continuing discussion about the Korea-Japan undersea tunnel, it is necessary to conduct a scientific investigation into tunnel deformation associated with large ground movements at fault. This paper presents findings obtained from numerical experiments to investigate a seismic lining that adopts rubber-like material. We utilized the user material subroutine to obtain the deformation gradient of the hyperelastic material. Additionally, polar decomposition is used to analyze the results, where the data is displayed on a series of two-dimensional planes using the principal direction, which facilitates a better insight into the deformation. Tunnel engineers could refer to this paper for the procedure to investigate the deformation of hyperelastic material.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.155-155
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• 2011

일반적으로 I형 보에 횡하중이 작용하는 경우, 횡 변위와 함께 회전을 동반하는 횡-비틀림 좌굴(Lateral-Torsional Buckling)이 발생하게 된다. 이러한 I형 보의 탄성 및 비탄성 횡-비틀림 좌굴에 대한 해석적 이론적 연구는 이미 많은 연구자들에 의해 수행되었다(Timoshenko 등, 1961; Galambos, 1963; Lindner, 1974; Trahair, 1993). I형 보의 비지지 길이 내 하중이 작용할 때 모멘트 구배계수(Cb)는 하중이 부재 단면에 작용하는 위치에 따라 달라지게 되는데 이를 하중고 효과(Load Height Effects)라고 한다. 탄성 영역 내 비지지길이가 존재하는 I형 보의 하중고 효과를 고려한 모멘트 구배계수 제안식은 Nethercot & Rockey(1971)에 의해 연구된 바 있다. 또한 Helwig 등(1997)은 Nethercot & Rockey(1971)의 제안식을 간략화 하여 탄성 영역 내 비지지길이가 존재하는 I형 보의 하중고 효과를 고려한 모멘트 구배계수식을 제안하였다. 그러나 현재까지 진행 된 하중고 효과에 대한 연구는 탄성 영역 내 비지지 길이가 존재하는 I형 보에 대한 제안식이며 현재까지 비탄성 영역 내 비지지 길이를 갖는 I형 보의 하중고 효과에 대한 연구는 진행된 바 없다. 본 연구는 비탄성 영역 내 비지지 길이가 존재하는 I형 보의 하중고 효과를 고려한 비탄성 횡-비틀림 좌굴강도에 대한 연구를 수행하였다. 하중조건으로는 집중하중 과 등분포 하중을 적용시켰으며, 비선형 횡-비틀림 좌굴 해석을 위해 잔류응력 및 초기변형을 고려하였다. Pi와 Trahair(1995)이 고려한 단순직선분포를 잔류응력으로 가정하였으며, 국내 I형강 표준 치수 허용치(현대제철, 2006)에 근거하여 부재 길이의 0.1%를 초기 최대 횡 변위로 적용하여 초기제작오차로 고려하였다. 유한요소해석결과를 바탕으로 Nethercot & Rockey(1971)와 Helwig 등(1997)의 연구내용을 바탕으로 범용구조해석 프로그램(ABAQUS, 2007)을 이용하여 비탄성 영역 내 존재하는 I형보의 횡-비틀림 좌굴강도를 산정하였다. 유한요소해석결과를 바탕으로 Nethercot & Rockey(1971)및 Helwig 등(1997)의 모멘트구배계수 제안식과 비교 분석 하였고 회기분석프로그램 MINITAB(2006)을 이용하여 비탄성 영역 내 비지지길이가 존재하는 I형보의 하중고 효과를 고려한 모멘트구배계수식을 개발 제안하였다. 본 연구에서 개발된 제안식은 경제적이고 합리적인 휨부재 강도평가에 적극 활용될 수 있으며, 비탄성 영역내 I형보의 횡-비틀림 좌굴강도 및 휨강도 연구에 널리 활용될 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.10
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• pp.896-901
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• 2015

The skin-frame type structure is designed to investigate the thermal deformation of the wing skin induced by the temperature gradient. In order to effectively simulate the temperature gradient on the wing specimen, a water cooling system is devised on the frame of the specimen. Out of surface skin deformation of the skin-frame type structure made of SUS304 material with respect to the temperature is successfully measured using the digital image correlation (DIC) technique including quantitative evaluation of the measurement uncertainty.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.104-108
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• 1992

국소가열 가공방법은 종래 사용 되어온 온간,열간 가공의 경우와는 달리 프레스 성형의 응력조건 또는 양긱,열(온도)에 의한 재료 성질의변화 등을 고려하여, 가공하는 박판의 필요 부분을 선택적으로가열, 냉각 또는 두가지를 조합하여 처리하는 것이다. 온도 구배의 영향이 박판 성형의 공정에 많은 영향을 줌에도 불구하고 종래의 박판 성형가공은 주로 열을 고려하지않은 성형해석이 대부분이었고 열을 고려 하였다라도 대 부분이 실험에의존 한 방법이었다. 그러나 실제의 공정 설계에서 실험만을 통한 공정 변수의규명은 많은 노 력과 시간을 필요로 하기 때문에 컴퓨터를 통한 시뮬레이션의 필요성이 대두 되었다. 본 연구는 박판 축대칭 온도 구배와, 변형해석을 유한 요소적 방법을 통해 행하고 이를 실제 공정 설계에 적용할 수있도록 도움을 주고자 하는 데에 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.347-352
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• 1999

The finite element formulation and simulation of drying process for ceramic electric insulators are investigated. The heat and moisture movements in green ceramics caused by the interaction of temperature gradient, moisture gradient, conduction, convection and evaporation are considered. The variations of temperature and moisture not only change the volume but also induce the hygro-thermal stress. The finite element formulation for solving the temperature and moisture distributions as well as the associated hygro-thermal stresses is derived. Using the computer code developed, the drying process of a ceramic electric insulator is simulated. Temperature distribution, moisture distribution, hygrothermal stress and deformed shape during the drying process are predicted.

• Journal of the Korea Computer Graphics Society
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• v.28 no.4
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• pp.13-22
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• 2022

In this paper, we propose a single framework based on the MPM(Material Point Method) that can represent the dynamic angular motion of the elementary particle unit. In this study, the particles can have various shapes while also describing linear and angular motion. As a result, unlike other particle-based simulations, which only represent linear movements of spherical (e.g. Circle, Sphere) particles, it is possible to express the visually dynamic motion of them. The proposed framework utilizes MPM, due to the fact that rotational motion can be decomposed and derived from large deformation. During the integration process of the presented technique, a deformation gradient tensor is decomposed by polar decomposition theory for extracting rotation tensor. By applying this together with the linear motion of each particle, as a result, it is possible to simultaneously express the angluar and linear motion of the particle itself. To verify the proposed method, we show the simulation of rotating particles scattering in the wind field, and the interaction(e.g. Collision) between a moving object and them by comparing the traditional MPM