• Title, Summary, Keyword: initial shape analysis

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A Study on the Shape Finding and Patterning Procedures for Membrane Structures (막구조의 초기형상 및 재단도 결정알고리즘에 관한 연구)

  • 한상을;이경수;이상주;유용주
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.298-305
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    • 1998
  • The purpose of this study is to propose the method of determining the initial fabric membrane structures surface and membrane patterning procedures. Tension structure, such as, fabric membrane structures and cable-net, is stabilized by their initial prestress and boundary condition. The process to find initial structural overall shape of tension structures produced by initial prestress called Shape Finding or Shape Analysis. One of the most important factor for the design of membrane structures is to search initial smooth surface, because unlike steel or concrete building elements which resist loads in bending, all tension structure forces are carried within the surface by membrane stress or cable tension. To obtain initial surface of fabric membrane element in large deformation analysis, the membrane element is idealized as cable using a technique with Force-density method. and that result is compared with well-known nonlinear numerical method, such as Newton-raphson method and Dynamic relaxation method. The shape resulting from Force-density method has been dealt with as the initial membrane shape and used patterning procedures.

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An Estimate for Convergence and Efficiency of Nonlinear Shape Analysis According to the Control Techniques (제어기법에 따른 비선형 형상해석의 수렴성 및 효율성 펑가)

  • Jeong, Eul-Seok;Jeon, Jin-Hyung;Shon, Su-Deog;Kim, Seung-Deog
    • Proceeding of KASS Symposium
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    • pp.214-223
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    • 2006
  • Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and happen large deformation phenomenon. Therefore, in this study, to find the structural shape after large deformation caused by initial stress, we need the shape analysis considering geometric nonlinear term. And we investigate the evaluation of shape analysis technique's convergence and efficiency according to the control method

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A Study on Cutting Pattern Generation of Membrane Structures by Using Geometric Line (막 구조물의 측지선을 이용한 재단도 생성에 관한 연구)

  • Ahn, Sang-Gil;Shon, Su-Deok;Kim, Seung-Deog
    • Proceeding of KASS Symposium
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    • pp.125-132
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    • 2005
  • Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and it happens large deformation phenomenon. And also there are highly varied in their size, curvature and material stiffness. So, the approximation inherent in cutting pattern generation methods is quite different. Therefore, in this study, to find the structural shape after large deformation caused by Initial stress, we need the shape analysis considering geometric nonlinear ten And the geodesic line on surface of initial equilibrium shape and the cutting pattern generation using the geodesic line is introduced.

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A Study on the Actual Equilibrium Analysis for Membrane Structures (막구조물의 준공평형 형상해석에 관한 연구)

  • 이장복;김재열;권택진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.61-68
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    • 2000
  • In general, the design of membrane structures takes three steps. The first is shape finding analysis which is determination of initial equilibrium geometry with uniform stresses. The second step involve the computation of the stress-deformation to get completed membrane under various load conditions. The third step is to divide the membrane structures into several plan strips from the initial equilibrium states. This procedure is needed because of the initial shape has usually undevelopable curved surface and is called as "cutting patterns generation". By introducing this work, the deformation due to the initial stress is removed and approximate cutting patterns are generated. In this approach, however, material properties is not considered, therefore the error between the design stresses and actual stresses during the fabrication of plan strips should be occurred. In this paper, actual equilibrium shape analysis procedure for HP shape models is presented. The deviations of stresses between the design stresses and actual stresses are estimated.

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A Study on the Optimal Initial Stress-Finding of Structures Stabilized by Cable-Tension (장력안정 구조물의 최적초기응력 탐색에 관한 연구)

  • 최옥훈;한상을;권택진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.287-294
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    • 1999
  • The tensegrity structure by prestressed cable, which may have large freedom in scale and form and therefore are received much attention from the view points of their light weight and aesthetics, is a very flexible and geometrically unstable structure because the cable material has little initial rigidity. For the stable self-equilibrated state of the usually very deformable structure, the method to find the optimal initial stress by the shape analysis is proposed in this paper. The proposed procedure is to derive the nonlinear finite element formula of cable and truss members considering geometric nonlinearity and used to modified load incremental method adding to Newton-Raphson method with the proposed condition for optimal initial stress. The result of the shape analysis for the tensegrity structure with the radius of 30m is shown the almost approximated shape to architectural shape and the changed procedure of initial stress

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Initial Shape Analysis of Suspension Bridge System under Dead Load (고정하중을 받는 현수교 시스템의 초기형상 결정법)

  • Kim, Min;Kim, Moon-Young
    • Journal of Korean Society of Steel Construction
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    • v.22 no.6
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    • pp.511-521
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    • 2010
  • This paper presents a simplified analysis method of determining the initial shape of suspension bridges, including the horizontal tension force of the main cable and the locations of each hanging point, considering the force equilibrium condition of each hanging point. This method is effective because it requires less effort than the methods used in other studies, for which complicated non-linear analysis was used, to comparatively determine the exact initial shape. The accuracy and validity of the present method are demonstrated by comparing the results of this study with those of previous researchers' numerical examples, including 2D and 3D models.

Development of Optimal Blank Shape Design Program Using the Initial Velocity of Boundary Nodes (초기 속도법을 이용한 최적 블랭크 설계 프로그램의 개발)

  • 심현보;이상헌;손기찬
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.77-81
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    • 2002
  • A new method of optimal blank shape design using the initial nodal velocity (INOV) has been proposed for the drawings of arbitrary shaped cups. With the given information of tool shape and the final product shape, corresponding initial blank shape has been found from the motion of boundary nodes. Although the sensitivity method, the past work of Hynbo Shim and Kichan Son, has been proved to be excellent method to find optimal blank shapes, the method has a problem that a couple of deformation analysis is required at each design step and it also exhibits an abnormal behaviors in the rigid body rotation prevailing region. In the present method INOV, only a single deformation analysis per each design stage is required. Drawings of practical products as well as oil-pan have been chosen as the examples. At every case the optimal blank shapes have been obtained only after a few times of modification without predetermined deformation path. The deformed shape with predicted optimal blank almost coincides with the target shape at every case. Through the investigation the INOV is found to be very effective in the arbitrary shaped drawing process design.

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Development of Optimal Blank Shape Design Program Using the Initial Velocity of Boundary Nodes (초기 속도법을 이용한 최적 블랭크 설계 프로그램의 개발)

  • 심현보;이상헌;손기찬
    • Transactions of Materials Processing
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    • v.11 no.6
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    • pp.487-494
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    • 2002
  • A new method of optimal blank shape design using the initial nodal velocity (INOV) has been proposed for the drawings of arbitrary shaped cups. With the given information of tool shape and the final product shape, corresponding initial blank shape has been found from the motion of boundary nodes. Although the sensitivity method, the past work of the present authors, has been proved to be excellent method to find optimal blank shapes, the method has a problem that a couple of deformation analysis is required at each design step and it also exhibits an abnormal behaviors in the rigid body rotation prevailing region. In the present method INOV, only a single deformation analysis per each design stage is required. Drawings of practical products as well as oil-pan, have been chosen as the examples. At every case the optimal blank shapes have been obtained only after a few times of modification without predetermined deformation path. The deformed shape with predicted optimal blank almost coincides with the target shape at every case. Through the investigation the INOV is found to be very effective in the arbitrary shaped drawing process design.

Automatic Tool Compensation for an UHSS Automotive Component Using a Compensation Module (금형보정 모듈을 이용한 초고강도강 자동차부품용 프레스금형의 자동보정)

  • Lee, J.H.;Kim, S.H.
    • Transactions of Materials Processing
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    • v.25 no.2
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    • pp.109-115
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    • 2016
  • In the current study, automatic tool compensation is accomplished by using a finite element stamping analysis for a center roof rail made of UHSS in order to satisfy the specifications for shape accuracy. The initial blank shape is calculated from a finite element inverse analysis and potential forming defects such as tearing and wrinkling are determined by the finite element stamping analysis based on the initial tool shape. The blank shape is optimized to meet the shape requirements of the final product with the stamping analysis, and die compensation is determined with the information about springback. The specifications for shape accuracy were successfully achieved by the proposed die compensation scheme using the finite element stamping analysis. The current study demonstrates that the compensation tendency is similar when the proposed scheme is used or when the compensation is performed by trial and error in the press-shop. This similarity verifies that the automatic compensation scheme can be used effectively in the first stage of tool design especially for components made from UHSS.

Three Dimensional Finite Element Inverse Analysis of Rectangular Cup and S-Rail Forming Processes using a Direct Mesh Mapping Method (직접 격자 사상법을 이용한 직사각컵 및 S-Rail 성형공정의 3차원 유한요소 역해석)

  • Kim S. H.;Huh H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.81-84
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    • 2001
  • An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of computation time and effort. In some drawing or stamping simulation with inverse method, it is difficult to apply inverse scheme due to the large aspect ratio or steep vertical angle of inclination. The reason is that initial guesses are hard to make out with present method for those cases. In this paper, a direct mesh marring scheme to generate initial guess on the sliding constraint surface described by finite element patches is suggested for one step inverse analysis to calculate initial blank shape. Radial type mapping is adopted for the simulation of rectangular cup drawing process with large aspect ratio and parallel type mapping for the simulation of S-Rail forming process with steep vertical angle of inclination.

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