• 한국산학기술학회논문지
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• 제14권7호
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• pp.3121-3126
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• 2013

원전 배관의 건전성평가는 원자로 안전을 위해 중요하며 결함발견 시 반드시 건전성을 확보해야만 한다. 균열을 갖는 구조물에 대한 정확한 응력확대계수 해석과 균열성장속도는 파괴강도와 피로수명을 평가하는데 필요로 한다. 피로설계와 수명평가는 배관, 산업공장장비 등과 같은 구조물을 설계하는데 극히 중요하다. 응력확대계수를 이용한 균열간의 상호 간섭해석은 유한요소법으로 구하였다. 내압을 받는 원통형구조물의 경우 표면균열의 인접점에서 간섭이 가장 크게 일어남을 확인하였다. 또한, 반복하중 균열에 대해서는 균열 성장평가와 더불어 피로하중에 의한 균열진전을 예측하기 위한 피로해석을 수행하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권1호
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• pp.57-65
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• 2011

In this paper, a good quality mesh generation for the finite element method is investigated for artificial hip joint simulations. In general, bad meshes with a large aspect ratio or mixed elements can give rise to excessively long computational running times and extremely high errors. Typically, hexahedral elements outperform tetrahedral elements during three-dimensional contact analysis using the finite element method. Therefore, it is essential to mesh biologic structures with hexahedral elements. Four meshing schemes for the finite element analysis of an artificial hip joint are presented and compared: (1) tetrahedral elements, (2) wedge and hexahedral elements, (3) open cubic box hexahedral elements, and (4) proposed hexahedral elements. The proposed meshing scheme is to partition a part before seeding so that we have a high quality three-dimensional mesh which consists of only hexahedral elements. The von Mises stress distributions were obtained and analyzed. We also performed mesh refinement convergence tests for all four cases.

• Geomechanics and Engineering
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• 제12권6호
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• pp.1021-1046
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• 2017

The assessment of slope stability is an essential task in geotechnical engineering. In this paper, a three-dimensional (3D) finite element analysis (FEA) was employed to investigate the performance of different shear pin arrangements to increase the stability of a soil block resting on an inclined plane with a low-interface friction plane. In the numerical models, the soil block was modeled by volume elements with linear elastic perfectly plastic material in a drained condition, while the shear pins were modeled by volume elements with linear elastic material. Interface elements were used along the bedding plane (bedding interface element) and around the shear pins (shear pin interface element) to simulate the soil-structure interaction. Bedding interface elements were used to capture the shear sliding of the soil on the low-interface friction plane while shear pin interface elements were used to model the shear bonding of the soil around the pins. A failure analysis was performed by means of the gravity loading method. The results of the 3D FEA with the numerical models were compared to those with the physical models for all cases. The effects of the number of shear pins, the shear pin locations, the different shear pin arrangements, the thickness and the width of the soil block and the associated failure mechanisms were discussed.

• Computers and Concrete
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• 제25권4호
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• pp.369-382
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• 2020

This paper presents a discussion of the Finite Element Analysis (FEA) when applied for the analysis of concrete elements reinforced with glass fibre reinforced polymer (GFRP) bars. The purpose of such nonlinear FEA model development is to create a tool that can be used for numerical parametric studies which can be used to extend the existing (and limited) experiment database. The presented research focuses on the numerical analyses of concrete beams reinforced with GFRP longitudinal and shear reinforcements. FEA of concrete members reinforced with linear elastic brittle reinforcements (like GFRP) presents unique challenges when compared to the analysis of members reinforced with plastic (steel) reinforcements, which are discussed in the paper. Specifically, the behaviour and failure of GFRP reinforced members are strongly influenced by the compressive response of concrete and thus modelling of concrete behaviour is essential for proper analysis. FEA was performed using the commercial software ABAQUS. A damaged-plasticity model was utilized to simulate the concrete behaviour. The influence of tension, compression, dilatancy, mesh, and reinforcement modelling was studied to replicate experimental test data of beams previously tested at the University of Waterloo, Canada. Recommendations for the finite element modelling of beams reinforced with GFRP longitudinal and shear reinforcements are offered. The knowledge gained from this research allows for the development of a rational methodology for modelling GFRP reinforced concrete beams, which subsequently can be used for extensive parametric studies and the formation of informed recommendations to design standards.

• Ocean and Polar Research
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• 제43권4호
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• pp.335-352
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• 2021

Trace elements in the ocean have been known as essential micronutrients for the primary production of phytoplankton and the growth of marine organisms. The GEOTRACES program beginning in the mid-2000 provided a new understanding of the distribution, origin and behavior of trace elements in the ocean, together with the establishment of both clean seawater sampling and trace element analysis techniques. The Indian Ocean, one of the major oceans, is relatively the least explored area, despite playing an important role in global climate variability. Although trace element observations have recently been conducted in the Indian Ocean by Japanese-and Indian scientists, relatively not much study has been done compared to the Atlantic, Pacific and Polar Regions. Recently, together with the launch of R/V Isabu, a 5,000-ton grade large- and comprehensive research vessel, the observations of trace elements has been conducted in the Indian Ocean for the first time in Korea since 2018. In this paper, we introduce the key results of currently conducted GEOTRACES expedition in the Indian Ocean to present future trace element research directions in the Indian Ocean, and also reviewed the preliminary results in the Indian Ocean studies from Korea. In the 2020s, new Indian Ocean GEOTRACES projects are planned around European countries, and it is time for Korea to prepare for the next phase of the trace element study in the Indian Ocean in line with these international trends.

• 대한건축학회논문집:계획계
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• 제36권4호
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• pp.3-11
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• 2020

The fireplace has been inseparable from the wall. Therefore, the fireplace, which is independently revealed in the living room, is unusual and exceptional. According to the concept of "Served-Servant space" by Louis Kahn, "Servant space" is conceived as an inhabited thick wall and completely separated from "Served space." The fireplace is an apparent servant element, but in Fisher house, it is considered as the single, remarkable and major element composing the house. Paradoxically, this scene of the living room is in conflict with Kahn's ideas on "Servant space." This study sheds new light on the independent fireplace in the conflicting relationship and suggests the similarities with the contemporary cases-Le Corbusier & Philip Johnson-in terms of the stand-alone "Servant element." In the end, the independent fireplace of the Fisher house has transformed into an essential element of the house, as Kahn said that "I feel it[fireplace] represents the presence of a man and therefore is of home."

• Structural Engineering and Mechanics
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• 제77권2호
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• pp.293-304
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• 2021

Structural failure due to seismic pounding between two adjacent buildings is one of the major concerns in the context of structural damage. Pounding between adjacent structures is a commonly observed phenomenon during major earthquakes. When modelling the structural response, stiffness of impact spring elements is considered to be one of the most important parameters when the impact force during collision of adjacent buildings is calculated. Determining valid and realistic stiffness values is essential in numerical simulations of pounding forces between adjacent buildings in order to achieve reasonable results. Several impact model stiffness values have been presented by various researchers to simulate pounding forces between adjacent structures. These values were mathematically calculated or estimated. In this study, a linear spring impact element model is used to simulate the pounding forces between two adjacent structures. An experimental model reported in literature was adopted to investigate the effect of different impact element stiffness k on the force intensity and number of impacts simulated by Finite Element (FE) analysis. Several numerical analyses have been conducted using SAP2000 and the collected results were used for further mathematical evaluations. The results of this study concluded the major factors that may actualise the stiffness value for impact element models. The number of impacts and the maximum impact force were found to be the core concept for finding the optimal range of stiffness values. For the experimental model investigated, the range of optimal stiffness values has also been presented and discussed.

• 한국기계가공학회지
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• 제21권9호
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• pp.85-91
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• 2022

The demand for electric vehicles has increased because of environmental regulations. The lithium-ion battery, the most widely used type of battery in electric vehicles, is composed of a cathode, an anode, and an electrolyte. It is manufactured according to the pole plate, assembly, and formation processes. To improve battery performance and increase manufacturing efficiency, the manufacturing process must be optimized. To do so, simulation can be used to reduce wasted resources and time, and a finite-element method can be utilized. For high simulation quality, it is essential to reflect the material properties of the electrode by considering the pores. However, the material properties of electrodes are difficult to derive through measurement. In this study, the representative volume element method, which is a homogenization method, was applied to estimate the representative material properties of the electrode considering the pores. The representative volume element method assumes that the strain energy before and after the conversion into a representative volume is conserved. The method can be converted into one representative property, even when nonhomogeneous materials are mixed in a unit volume. In this study, the material properties of the electrode considering the pores were derived. The results should be helpful in optimizing the electrode manufacturing process and related element technologies.

• Structural Engineering and Mechanics
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• 제52권2호
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• pp.261-274
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• 2014

An accurate finite element (FE) model of a structure is essential for predicting reliably its dynamic characteristics. Such a model is used to predict the effects of structural modifications for dynamic design of the structure. These modifications may be imposed by design alterations for operating reasons. Most of the model updating techniques neglect damping and so these updated models can't be used for accurate prediction of vibration amplitudes. This paper deals with the basic formulation of damped finite element model updating method and its use for structural dynamic modifications. In this damped damped finite element model updating method, damping matrices are updated along with mass and stiffness matrices. The damping matrices are updated by updating the damping coefficients. A case involving actual measured data for the case of F-shaped test structure, which resembles the skeleton of a drilling machine is used to evaluate the effectiveness of damped FE model updating method for accurate prediction of the vibration levels and thus its use for structural dynamic modifications. It can be concluded from the study that damped updated FE model updating can be used for structural dynamic modifications with confidence.

• 소성∙가공
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• 제21권7호
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• pp.403-411
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• 2012

The aim of this study was to predict the results of superplastic forming on magnesium alloy, by considering the grain growth using numerical simulations. Superplastic behavior of AZ31 alloy was investigated through a set of uniaxial tensile tests that cover the forming temperatures ranges from 375 to $450^{\circ}C$. All the material parameters in the model, which consists of a constitutive equation and a grain growth equation, were determined. The model was used in the finite element analysis for uniaxial tensile tests and superplastic blow forming, through a user-subroutine available within ABAQUS. From this study, the effect of grain growth during forming was evaluated. The results show that it is essential to include the effect of grain growth in predicting the behavior during superplastic forming of this magnesium alloy.