• 한국지반환경공학회 논문집
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• 제15권5호
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• pp.13-21
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• 2014

본 연구에서는 쉴드 TBM 공법의 다양한 세그먼트 모델링 기법에 따른 비교 해석을 통하여 해석기법에 따른 차이를 분석하고 이에 따른 합리적인 모델링 기법을 제안하였다. 또한 암반 이완하중 산정모델에 따른 하중 분석 및 3차원 유한요소해석을 통하여 실제 현장에서 적용 가능한 합리적인 하중산정 방법을 제시하였다. 암반분류에 의한 이완영역의 산정방법은 암반등급이 높은 지반에서는 결과의 차이가 크지 않으나 지반등급이 낮은 지반에서는 그 차이가 매우 크게 나타났으며, 3차원 해석에 의한 이완영역 산정결과 지반등급이 낮은 지반의 이완영역은 각 방법의 중간 정도 범위에 위치할 것으로 예측되었으며 지반등급이 낮은 지반의 세그먼트 계획 시에는 기계식 터널 굴착 특성을 반영한 3차원 해석을 통한 이완영역의 산정을 적극 검토할 필요가 있다.

• 한국소음진동공학회논문집
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• 제17권2호
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• pp.105-113
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• 2007

In this study, three-dimensional rotordynamic analyses have been conducted using equivalent beam, hybrid and full three-dimensional models. The present computational method is based on the general finite element method with rotating gyroscopic effects of the rotor system. General purpose commercial finite element code, SAMCEF which includes practical rotordynamics module with various types of rotor analysis tools and bearing elements is applied. For the purpose of numerical verification, comparison study for a benchmark rotor model with support bearings is performed first. Detailed finite element models based on three different modeling concepts are constructed and then computational analyses are conducted for the realistic and complex three-dimensional rotor system. The results for rotor stability and mass unbalance response are presented and compared with the experimental vibration test data conducted herein.

• 대한조선학회논문집
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• 제34권3호
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• pp.76-84
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• 1997

초기설계 단계에서는 선체구조 강도의 신속한 해석을 위해 보요소를 사용한 유한요소 해석이 일반적으로 사용된다. 선체구조를 보요소로 모델링할 때, 브라켓은 해석의 간편화를 위해 강체 요소로 표시된다. 강체 단부의 길이(=span point)는 세 가지 관점 - 굽힘, 전단, 축 변형 - 에 따라서 결정된다. 본 논문에서는, 새로운 2차원 보요소를 개발하였고, 2차원 해석으로 3차원 해석을 대신할 수 있는 방법을 제안하였다. '강체 단부 보요소' 라고 명명된 이 보요소는 한 요소 내에서 세 종류의 span point 효과를 모두 고려할 수 있는데, 이것은 보통의 보요소에서는 불가능한 것이다. 강체 단부 보요소를 사용한 Portal frame 해석결과는 membrane 해석결과와 잘 일치한다. 그리고, 영향계수를 사용한 2단계 해석을 포함하는 준 3차원 해석결과는 좋은 정확도를 보이고 있다. 강체 단부 보요소와 준 3차원 해석방법을 사용한 구조해석은 브라켓에 해당하는 요소가 필요치 않고, 3차원 해석을 단순화시킬 수 있었기 때문에 좋은 계산효율을 가진 것으로 판명되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.79-86
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• 2000

This paper presents the results of a parametric study on the behavior of tunnel face reinforced with horizontal pipes. A series of reduced-scale model tests was carried out to in an attempt to verify previously performed three-dimensional numerical modeling and to investigate effects of reinforcement layout on the tunnel face deformation behavior The results of model tests indicate that the tunnel face deformation can significantly reduced by pre-reinforcing the tunnel face with longitudinal members and thus enhancing the tunnel stability. In addition, the model tests results compare fairly well with those from the previously performed three-dimensional finite element analysis. Therefore, a properly calibrated three dimensional model may effectively be used in the study of tunnel face reinforcing technique.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.275-280
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• 2004

Shape optimization was performed to obtain the precise shape of cutouts including the internal shape of cutouts in laminated composite plates by three dimensional modeling using solid element. The volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. The volume control of the growth-strain method makes Tsai-Hill failure index at each element uniform in laminated composites under the initial volume. Then shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study. (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsal-Hill failure index was reduced up to 67% when shape optimization was peformed under the initial volume by volume control of growth-strain method.

• International Journal of Aeronautical and Space Sciences
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• 제1권1호
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• pp.36-47
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• 2000

Three-dimensional compressible turbulent flow fields within the passage of a diffusing S-duct have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The average inlet Mach number is 0.6 and the Reynolds number based on the inlet diameter is $1.76{\times}10^6$ The extended $k-{\varepsilon}$ turbulence model is applied to modeling the Reynolds stresses. Computed results of the flow in a circular diffusing S-duct provide an understanding of the flow structure within a typical engine inlet system. These are compared with experimental wall static-pressure, total-pressure fields, and secondary velocity profiles. Additionally, boundary layer thickness, skin friction values, and streamlines in the symmetric plane are presented. The computed results depict the interaction between the low energy flow by the flow separation and the high energy flow by the reversed duct curvature. The computed results obtained using the extended $k-{\varepsilon}$ turbulence model.

• Computers and Concrete
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• 제8권3호
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• pp.327-341
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• 2011

Three-dimensional graphic objects created by MATLAB are exported to the AUTOCAD program through the MATLAB handle functions. The imported SAT format files are used to produce the finite element mesh for MSC.PATRAN. Based on the Monte-Carlo random sample principle, the material heterogeneity of cement composites with randomly distributed fibers is described by the WEIBULL distribution function. In this paper, a concept called "soft region" including micro-defects, micro-voids, etc. is put forward for the simulation of crack propagation in fiber-reinforced cement composites. The performance of the numerical model is demonstrated by several examples involving crack initiation and growth in the composites under three-dimensional stress conditions: tensile loading; compressive loading and crack growth along a bimaterial interface.

• 대한기계학회논문집B
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• 제23권1호
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• pp.82-91
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• 1999

A numerical analysis based on the three-dimensional Reynolds-averaged Navier-Stokes equation has been conducted to investigate the flow within a NASA rotor 67 transonic fan. General coordinate transformations are used to represent the complex blade geometry and an H-type grid is used. The governing equations are solved using implicit LU-SGS scheme for the time-marching integration and a standard ${\kappa}-{\varepsilon}$ model is used with wall functions for the turbulence modeling. The computations are compared with the experimental data and a detailed study of the flow structures near peak efficiency and near stall is presented. The calculated overall aerodynamic efficiency and three-dimensional shock system agree well with the laser anemometer data.

• 한국정밀공학회지
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• 제22권7호
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• pp.79-87
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• 2005

This paper summarizes the work on the development of a simulation program for modelling the process of machining quasi-three dimensional shape with the excimer laser beam on a constantly moving polymers. Relatively simple masks of rectangle, triangle and half circle shape are considered. The etching depth is calculated by considering the number of laser pulses irradiated on the specimen surface. It was found that similar shapes as experimental results can be obtained by choosing suitable parameters of moving velocity, moving distance and mask sizes.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.743-754
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• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.