• Journal of Korean Society for Geospatial Information Science
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• v.24 no.1
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• pp.17-24
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• 2016

At present, summer cloudburst and local torrential rainfalls have increased in this country, because of climatic change. Therefore, studies on prevention of soil loss have been actively proceeded, and Korea Forest Service has offered landslide hazard map. Landslide hazard map divides risks into 5 classes, by giving weight with 9 kinds of elements. In August 25 2014, soil loss occurred in the whole Oryun Tunnel, Geumjeong-gu, Busan, because of local torrential heavy rain. As a result of comparing with landslide hazard map, the area where soil loss occurred in reality is a safety zone on hazard map. Rainfall, soil map, geological map, forest type map, gradient, drainage network, watershed, basin shape, and efflux of the whole Oryun Tunnel where soil loss occurred were analyzed. As a result of an analysis, it is judged that soil, forest type, much efflux and peak discharge, degree of water network and basin shape of a place where landslide occurred are causes of soil loss. It is judged that efflux, peak discharge, and basin shape by the localized rainfall that is not considered in landslide hazard map of them are the biggest causes of soil loss. It is judged that efflux, peak discharge, degree of water network and basin shape by the rainfall are important through a study on a causual analysis on soil loss in the whole Oryun Tunnel where is one of occurrence area where a lot of propertywere lost by the record local torrential rainfalls. A localized torrential downpour should be prepared by considering these elements on judgement of a landslide hazard area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.379-387
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• 2012

This study investigates free vibration characteristics of new energy harvesting multi-layer block structures with different geometrical shapes using solid and shell finite elements and evaluate their piezoelectric effect on experiments. The two and three-dimensional finite element (FE) delamination models for block structures described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the entire vibration mode shape. The FE model using ABAQUS is used for studying free vibrations of multi-layer block structures for various tip mass and PZT. In particular, new results reported in this paper are focused on the significant effects of the global and local vibration modes for various parameters, such as size of block shape, existence of tip mass and hole, and location of tip mass and PZT. In addition, we evaluate the power generation capacity of developed energy block structures through a laboratory-scale experiment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.609-615
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• 2012

In LSP (laser shock peening) treatment, the laser source geometries when the laser beam strikes the metal target area are diverse. The laser spot geometry affects the residual stress field beneath the treated surface of the metallic materials, which determines the characteristics of the pressure pulse. In this paper, detailed finite-element (FE) simulations on laser shock peening have been conducted in order to predict the magnitude and of the residual stresses and the depth affected in Inconel alloy 600 steel. The residual stress results are compared for circular, rectangular, and elliptical laser spot geometries. It is found that a circular spot can produce the maximum compressive residual stresses near the surface but generates tensile residual stresses at the center of the laser spot. In the depth direction, an elliptical laser spot produces the maximum compressive residual stresses. Circular and elliptical spots plastically affect the alloy to higher depths than a rectangular spot.

• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.559-570
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• 2014

In this study, compression and shear characteristics of laminated rubber bearings and lead rubber bearings with various parameters are investigated by using material and geometric nonlinear three-dimensional finite element analysis. Rubber coupon tests are performed to make a model of the laminated rubber bearings. In addition, the material constants of the rubber are calculated by the curve fitting process of stress-strain relationship. The finite element analysis and experimental tests of the laminate rubber bearings are used to verify the validity of the rubber material constants. It is seen that the compression behavior of the laminated rubber bearings and lead rubber bearings mainly varies depending on the first shape factors and their shear behavior significantly varies depending on the second shape factors. In addition, the horizontal stiffness and energy dissipation capacity of lead rubber bearing are increased when the diameter of a lead bar is increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.703-709
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• 2017

Creep analysis takes much more time than elastic or elastic-plastic analysis. In this study, we conducted elastic and elastic-plastic analysis and compared the results with creep analysis results. In the elastic analysis, we used primary stress, which can be classified by the $M{\alpha}-tangent$ method and stress intensities recommended in the ASME code. In the elastic-plastic analysis, we calculated the parameters recommended in the R5 code. For the FE models, a bending load, uniaxial load, and biaxial load were applied to the cross shaped welded plate, and a bending load and internal pressure were applied to the elbow pipe. To investigate the element size sensitivity, we conducted FE analysis for various element sizes for the cases where bending load was applied to the cross shaped welded plate. There was no significant difference between the creep stress and the alternative methods; however, in the $M{\alpha}-tangent$ method, the results were affected by the element size.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.243-249
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• 2005

Structural behavior of lattice girders of different loading conditions, loading patterns and shapes was analyzed by MIDAS, the finite element method. Optimal condition for lattice girders was represented.

• Geotechnical Engineering
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• v.14 no.1
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• pp.93-108
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• 1998

In this study, the analytic solutions and numerical methods were used to estimate the shape and size effects on the stability of underground openings. The stability of underground openings was evaluated by scrutinizing the effects of the rock mass quality, the state of in-situ stresses and the lateral earth pressure coefficient on the displacement, the stress concentration and the plastic region developed in the vicinity of the openings. The analytic solutions have shown that the stress concentration factor is inversely proportional to the radius of curvature of openings. Through parametric study on the various shapes and sizes of underground openings the characteristics of the controlling factors concerned with the stability were analyzed. Then, the study was extended to the horseshoe-shaped openings commonly used for under ground storage. Through the extended study the effects of the stress ratio and the height-towidth ratio of openings on the maximum displacement and plastic region developed around the openings were estimated. The results have shorn that the height-to-width ratio of domestic storage caverns can be increased economically without stability problem, as far as the lateral earth pressure coefficient is appropriate.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.798-799
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• 2015

본 논문에서는 영구자석의 형상을 변화시켜 표면 부착형 동기 전동기(Surface Permanent Magnet Synchronous Motor, SPMSM)의 토크리플을 저감하였다. 교류전동기의 경우 공극에 자속이 정현적으로 분포할수록 역기전력 파형이 정현파에 가까워지고, 토크리플이 작아진다. 위의 조건을 바탕으로, 자석의 사용 양을 동일하게 유지하면서 공간고조파를 최소화하기 위해 공극에 자속이 정현적으로 분포할 수 있도록 자석 형상에 모깎기를 적용하여 SPMSM의 최적설계를 진행하였다. 2D 유한요소해석법(Finite Element Method)을 이용하여 각 형상별 토크, 역기전력 등의 모터의 기본 특성들을 해석하여 영구자석 형상이 SPMSM의 성능에 어떠한 영향을 미치는지 분석하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.388-391
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• 2011

이 논문에서는 인도의 BARC에서 가압중수형 격납건물의 선형탄성 거동 및 균열의 발생형상과 극한내압 평가를 위해서 건설한 1/4 축소모델 격납건물에 대하여 실험한 결과와 유한요소 해석에 의한 결과를 비교 분석하였다. 유한요소 해석은 상용프로그램인 ABAQUS를 이용하였고 각각의 구조재료에 대한 수치 해석모델을 작성하여 내압해석을 수행하였다.

• 전기의세계
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• v.44 no.3
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• pp.9-14
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• 1995

비정질 core의 Butt-lap-step joint model의 자계를 유한요소법을 이용하여 해석한 결과, step당 리본 수의 변화, 설계자속밀도의 변화, 코아 연결부의 형상 변화에 따른 특성을 분석하면 다음과 같이 요약할 수 있다. (1) Step당 리본 수의 변화에 따른 영향에서 리본수가 작을수록 코아 전체의 flux density의 편차가 작으며 최대값 역시 낮으므로 유리하다. (2) 설계자속밀도의 변화에 따른 코아 부위의 자속 변화는 인가하는 설계자속밀도의 값이 높을수록 균일한 자장 분포를 얻을 수 있다. (3) 코아의 적층 방법의 변화에서는 Butt-Lap-Step방식이 가장 유리한 결과를 얻을 수 있었지만 코아 곡률부의 형상 변화가 중요한 요소로 작용한다. (4) 최적 step수, ribbon/group 수, airgap 길이 등은 전체 model의 특성, 손실, 제작성 등을 고려하여 결정하는 것이 바람직하며, 유한요소법의 해석으로는 전체적인 비정질 코아 변압기의 전기적인 특성과 경향을 도식화하여 설계자에게 좋은 설계방향과 정보를 제공할 수 있게 된다. 또한 비정질 코아의 특성상 종래의 일반적인 유한요소법으로는 많은 계산시간과 큰 computer system을 요구하는 core의 미세부분의 해석은 새로운 계산기법을 도입하여 계산해야 할 것이다. 이러한 문제해결을 위하여 3절에서 설명한 Asymptotic Expansion을 이용하여 균질화(homogenized)된 투자율 (또는 reluctivity)를 산출하고, 여기에 유한요소기법을 도입하여 단점을 보완한 새로운 기법의 algorithm을 개발하고 있으며, 이 기법은 계산시간의 단축과 Microscopic하게 자속밀도 분포를 관찰 할 수 있으므로 joint 부분의 자속경로와 손실 등 비정질 코아의 설계 Parameter를 설정하는 결정적인 역할을 할수 있을 것으로 기대된다.