• Structural Engineering and Mechanics
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• 제5권6호
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• pp.853-865
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• 1997

The design of robust plate and shell elements has been a very challenging area for several decades. The main difficulty has been the shear locking phenomenon in plate elements and the shear and membrane locking phenomena together in the shell elements. Among the various artifices or devices which are used to develop elements free of these problems is the field-consistency approach. In this paper this approach is reviewed, It turns out that not only Mindlin type elements but also elements based on higher-order theories could be developed using the technique.

• 한국정밀공학회지
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• 제17권4호
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• pp.226-232
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• 2000

This paper develops a finite element model for studying the crashworthiness analysis of a mid-size truck. A simulation for a truck frontal crash to a rigid barrier using the model is performed with PAM-CRASH installed in super computer SP2. Full vehicle model is composed of 86467 shell elements, 165 beam elements and 98 bar elements, and 86769 nodes. The model uses four material model such as elastic, elastic-plastic(steel), rigid and elastic-plastic(rubber) material model which are in PAM-CRASH. Frame and suspension system are modeled with 28774 shell elements and 31412 nodes. Cab is modeled with 34680 shell elements and 57 beam elements, and 36254 nodes. Bumper is modeled with 2262 shell elements, and 2508 nodes. Axle, steering shaft, etc are modeled using beam or bar elements. Mounting parts are modeled using rigid bodies. Bodies are interconnected using nodal constrains or joint options. To verify the developed model, frontal crash test with 30mph velocity to a rigid barrier is carried out. In the crash test, vehicle pulse at lower part of b-pillar is measured, and deformed shapes of frame and driver seat area are photographed. Those measured vehicle pulse and photographed pictures are compared those from the simulation to verify the developed finite element model.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.3-17
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• 2003

This paper deals with the problems and their possible solutions in the development of finite element for analysis of shell. Based on these solution schemes, a series of flat shell elements are established which show no signs of membrane locking and other defects even though the coarse meshes are used. In the element formulation, non-conforming displacement modes are extensively used for improvement of element behaviors. A number of numerical tests are performed to prove the validity of the solutions to the problems involved in establishing a series of high performance flat shell elements. The test results reveal among others that the high accuracy and fast convergence characteristics of the elements are obtainable by the use of various non-conforming modes and that the ‘Direct Modification Method’ is a very useful tool for non-conforming elements to pass the patch tests. Furthermore, hierarchical and higher order non-conforming modes are proved to be very efficient not only to make an element insensitive to the mesh distortion but also to remove the membrane locking. Some numerical examples are solved to demonstrate the validity and applicability of the presented elements to practical engineering shell problems.

• Structural Engineering and Mechanics
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• 제18권2호
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• pp.211-229
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• 2004

The main purpose of this paper is the numerical analysis of the non-linear seismic response of a RC building mock-up. The mock-up is subjected to different synthetic horizontal seismic excitations. The numerical approach is based on a 3D-model involving multilayered shell elements. These elements are composed of several single-layer membranes with various eccentricities. Bending effects are included through these eccentricities. Basic equations are first written for a single membrane element with its own eccentricity and then generalised to the multilayered shell element by superposition. The multilayered shell is considered as a classical shell element : all information about non-linear constitutive relations are investigated at the local scale of each layer, whereas balance and kinematics are checked afterwards at global scale. The non-linear dynamic response of the building is computed with Newmark algorithm. The numerical dynamic results (blind simulations) are considered in the linear and non linear cases and compared with experimental results from shaking table tests. Multilayered shell elements are found to be a promising tool for predictive computations of RC structures behaviour under 3D seismic loadings. This study was part of the CAMUS International Benchmark.

• Structural Engineering and Mechanics
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• 제6권8호
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• pp.883-899
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• 1998

The strength, deformation and buckling of a large engineering structure consisting of four ellipsoidal shells, two cylindrical shells with stiffening ribs and large holes, one conical shell and three pairs of large flanges under external pressure, self weight and heat sinks have been analysed by using two kinds of five different finite elements - four assumed displacement finite elements (shell element with curved surfaces, axisymmetric conical shell element with variable thickness, three dimensional eccentric beam element, axisymmetric solid revolutionary element) and an assumed stress hybrid element (a 3-dimensional special element developed by authors). The compatibility between different elements is enforced. The strength analyses of the top cover and the main vessel are described in the paper.

• 한국CDE학회논문집
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• 제11권1호
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• pp.41-48
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• 2006

This paper describes hexahedral mesh generation for various shell structures, such as automobile bodies, plastic injection mold components and sheet metal parts by using chordal surfaces. After generaling one-layered tetrahedral mesh by an advancing front algorithm, the chordal surfaces are constructed by cutting of tetrahedral elements. Since the choral surfaces are composed of tri/quad elements with poor quality, they are transformed into quadrilateral elements with good quality. Hexahedral elements are then generated by offsetting these quadrilateral elements. The boundary nodes of hexahedral elements are generated on the outer surfaces of the original shell structures. Sample models including nonuniform thickness have been tested to validate the proposed algorithm.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1988년도 가을 학술발표회 논문집
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• pp.24-29
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• 1988

In this paper, it is proposed hew the rigid element method suggested in the first paper can be applied to the elastic and elasto-plastic analysis of spherical shell with the open stiff ring. In the analytical model, the solution domain is divided into rectangular-shaped spherical bending elements. Each contact surface of two adjacent elements is interconnected with four elastic springs, and it is assumed that the internal forces are distritributed into springs. The 6 degrees of freedom of the element are placed in the center of elements, and the 6 cen-teroidal rigid displacements affect other elements through springs around elements. And then the solution domain is estimated by the behavior of elements and springs. In this study, these concepts are applied to the elastic and elasto-plastic analysis for the eight cases of the spherical shell according to the condition of stiff ring, the condion of loading and the size of opening. And then some numerical results such as the distribution of stresses, the force-displacement curves and the mode of fractures will he shown.

• 한국전자파학회논문지
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• 제19권7호
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• pp.707-712
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• 2008

본 논문에서는 3중(4+8+4-소자) 순차 회전 배열을 기본 부 배열로 하는 256-소자 순차 회전 배열 안테나를 설계하였다. 본 3중(4+8+4-소자) 순차 회전 배열 안테나는 3개의 동심 각으로 구성되어 있으며, 내각과 외각에는 각각 4개의 소자가, 중간 각에는 8개의 소자가 배열되어 있다. 안테나 이득을 극대로 하기 위하여 내각과 외각의 배열인자를 M=4, P=1로, 중간 각에 는 M=8, P=1로 하였다. 제안하는 3중(4+8+4)-소자 순차 배열 안테나와 256-소자 순차 회전 배열 안테나에 대한 모의분석 및 실험 결과들을 비교했을 때 집적도, 교차 편파준위 및 이득 특성 측면에서 모두 우수한 특성을 보였다.

• 한국항공우주학회지
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• 제33권2호
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• pp.46-53
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• 2005

곡면 사각형 쉘 요소들이 다수인 것에 비해, 곡면 삼각형 요소들은 아주 소수이다. 이미 발표된, 선형 해석을 위한 6절점 2차 쉘 요소의 가정 자연 변형도 이론에 기초해, 본 연구에서는 6절점 쉘 요소의 기하학적 비선형 해석을 수행하였다. 쉘 요소는 표준 절점 자유도만으로 곡면 모델링이 가능하고, 수치해석 결과가 보여주는 바와 같이 다양한 잠김 현상들을 제거하는데 효율적인 요소임을 확인하였다.

• Structural Engineering and Mechanics
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• 제6권1호
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• pp.41-61
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• 1998

A state-of-the-art report on the new finite elements formulated by the addition of nonconforming displacement modes has been presented. The development of a series improved nonconforming finite elements for the analysis of plate and shell structures is described in the first part of this paper. These new plate and shell finite elements are established by the combined use of different improvement schemes such as; the addition of nonconforming modes, the reduced (or selective) integration, and the construction of the substitute shear strain fields. The improvement achieved may be attributable to the fact that the merits of these improvement techniques are merged into the formation of the new elements in a complementary manner. It is shown that the results obtained by the new elements give significantly improved solutions without any serious defects such as; the shear locking, spurious zero energy mode for the linear as well as nonlinear benchmark problems. Recent developments in the transition elements that have a variable number of mid-side nodes and can be effectively used in the adaptive mesh refinement are presented in the second part. Finally, the nonconforming transition flat shell elements with drilling degrees of freedom are also presented.