• Title/Summary/Keyword: Plane strain forming

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Effect of Out-of- Plane Stress on the theoretical Forming Limit Strain of Sheet Metals (판재의 이론적 변형한계 스트레인의 면외압 의존성)

  • 정태훈
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.10a
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    • pp.162-169
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    • 2004
  • In press forming of sheet metals, the material sheet is usually subjected to very large plastic strain under in-plane stressing. Moreover, the sheet also very often is subjected to out-of-plane compressive force between tools such as the upper and lower dies, the blank holder and the die, and so forth. In this paper, it is clearly demonstrated theoretically that out-of-plane stress may notably raise the forming limit strain and thus it can be effectively utilized to avoid earlier fracture of the sheet in press forming.

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Nonsteady Plane-strain Ideal Forming without Elastic Dead-zone

  • Chung, Kwansoo;Lee, Wonoh;Kang, Tae Jin;Youn, Jae Ryoun
    • Fibers and Polymers
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    • v.3 no.3
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    • pp.120-127
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    • 2002
  • Ever since the ideal forming theory has been developed for process design purposes, application has been limited to sheet forming and, for bulk forming, to two-dimensional steady flow. Here, application for the non-steady case was made under the plane-strain condition. In the ideal flow, material elements deform fellowing the minimum plastic work path (or mostly proportional true strain path) so that the ideal plane-strain flow can be effectively described using the two-dimensional orthogonal convective coordinate system. Besides kinematics, schemes to optimize preform shapes for a prescribed final part shape and also to define the evolution of shapes and frictionless boundary tractions were developed. Discussions include numerical calculations made for a real automotive part under forging.

Localized necking condition of sheet metals is subjected to out-of plane force (면외압을 받는 판재의 국부네킹 발생 조건)

  • 정태훈
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2002.04a
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    • pp.579-584
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    • 2002
  • In press forming of sheet metals, the material sheet is usually subjected to very large plastic strain under in-plane stressing. Moreover, the sheet also very often is subjected to out-of-plane compressive force between tools such as the upper and lower dies, the blank holder and the die, and so forth. In this paper, it is clearly demonstrated theoretically that out-of-plane stress may notably raise the forming limit strain and thus it cm be effectively utilized to avoid earlier fracture of the sheet in press forming.

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Nonsteady Plane-strain ideal forming with elastic dead zone (탄성 변형 영역을 고려한 비정상 평면 변형 이상 공정 이론)

  • Lee W.;Chung K.;Richmond Owen
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.05a
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    • pp.190-193
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    • 2004
  • Ever since the ideal forming theory has been developed fur process design purposes, application has been limited to sheet forming and, for bulk forming, to two-dimensional steady flow. Here, application for the non-steady case was performed under the plane-strain condition based on the theory previously developed. In the ideal flow, material elements deform following the minimum plastic work path (or mostly proportional true strain path) so that the ideal plane-strain flow can be effectively described using the two-dimensional orthogonal convective coordinate system. Besides kinematics, for a prescribed final part shape, schemes to optimize a preform shape out of a class of initial configurations and also to define the evolution of shapes and boundary tractions were developed. Discussions include the two problematic issues on internal tractions and the non-monotonous straining. For demonstration purposes, numerical calculations were made for a bulk part under forging.

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Non-steady Ideal Forming in Plane Strain (평면 변형 하에서의 비정상 이상 공정 이론)

  • ;;Owen Richmond
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2002.05a
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    • pp.66-69
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    • 2002
  • In the ideal forming theory(1), which has been deviously developed as a direct method for optimizing forming process, material elements are required to deform following the minimum plastic work path (or the proportional true strain path). Besides the general theory(2,3), specific ideal forming theories have been developed for membrane sheet forming(4) as well as two-dimensional steady bulk forming(5-7). In this work, the ideal forming theory was successfully applied for non-steady bulk forming under the plane strain condition. Here, the shape change complying with the minimum plastic work path, was effectively described by developing a numerical code based on the characteristic method. Numerical results obtained for a specific industrial part also include the optimum pre-forming shape and its evolving shape change to the final shape as well as the boundary traction history.

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Thin Steel Sheet Roll Forming and Load Analysis (박판강대의 롤성형 및 부하 분석)

  • 서정현
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1999.03b
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    • pp.273-279
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    • 1999
  • In this paper the stress and strain behaivor in near homogeneous isotropic matrix of metal like steel was studied roll forming of thin steel sheet for cylindrical pipe. Analytical results reveals a body which is on the area of square thickness along and perpendicular to the width of thin steel sheet is in the state of plane strain during roll forming. As a result construction of analytical method for calculating deformation load and stably deformed length along the width of strained steel sheet was established. Also loads applied during roll forming were analyzed using two typical thin steel sheet 12.3m thick steel sheet with 42.5kg /mm2 yield strength of pipe and 5.3mm thick steel sheet with 32.5kg/mm2 yield strength of pipe. Through this analysis applicability of the analytical method for deformation load during roll forming of cylindrical thin steel pipe was evaluated with a study of necessary production technology for roll forming and design technology for roll forming machine.

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Thin Steel Sheet Roll Forming and Load Analysis (박판 강대의 롤성형 및 부하 분석)

  • 서정현
    • Transactions of Materials Processing
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    • v.8 no.6
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    • pp.554-562
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    • 1999
  • In this paper, the stress and strain behavior in near homogeneous isotropic matrix of metal like steel was studied during roll forming of thin steel sheet for cylindrical pipe. Analytical result reveals a body which is on the area of square thickness along and perpendicular to the width of thin steel sheet is in the state of plane strain during roll forming. As a result, construction of analytical method for calculating deformation load and stably deformed length along the width of strained steel sheet was established. Also, loads applied during roll forming were analyzed using two typical thin steel sheets. 12.3mm thick steel sheet with 42.5kg/㎟ yield strength of pipe and 5.3mm thick steel sheet with 32.5kg/㎟ yield strength of pipe. Through this analysis, applicability of the analytical method for deformation load during roll forming of cylindrical thin steel pipe was evaluated with a study of necessary production technology for roll forming and design technology for roll forming machine.

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Plane-Strain Analysis of Auto-Body Panel Using the Rigid-Plastic Finite Element Method (강소성 유한요소법을 이용한 자동차 판넬 성형공정의 평면 변형해석)

  • 양동열;정완진;송인섭;전기찬;유동진;이정우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.1
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    • pp.169-178
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    • 1991
  • A plane-strain finite element analysis of sheet metal forming is carried out by using the rigid-plastic FEM based on the membrane theory. The sheet material is assumed to possess normal anisotropy and to obey Hill's new yield criterion and its associated flow rule. A formulation of initial guess generation for the displacement field is derived by using the nonlinear elastic FEM. A method of contact treatment is proposed in which the skew boundary condition for arbitrarily shaped tools is successively used during iteration. In order to verify the validity of the developed method, plane-strain drawing with tools in analytic expression and with arbitrarily shaped tools is analyzed and compared with the published results. The comparison shows that the present method can be effectively used in the analysis of plane-strain sheet metal forming and thus provides the basis of approximate sectional analysis of panel-like sheet forming.

Plane Strain Analysis of Sheet Metal with Arbitrary Forming Conditions (임의의 성형조건을 갖는 박판의 평면변형율 해석)

  • Keum, Y.T.;Lee, S.Y.;Wagoner, R.H.
    • Transactions of Materials Processing
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    • v.1 no.1
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    • pp.95-103
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    • 1992
  • The plane strain analysis for simulating the stretch/draw forming operation with an arbitrarily-shaped tool profile is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The linear line elements are used for depicting the formed sheet, based on membrane approximation. The FEM formulation is tested in the sections of automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains is obtained in the stretched section, but also the numerical stability of formulation is verified in the draw-in section.

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Yield function of the orthotropic material considering the crystallographic texture

  • Erisov, Yaroslav A.;Grechnikov, Fedor V.;Surudin, Sergei V.
    • Structural Engineering and Mechanics
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    • v.58 no.4
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    • pp.677-687
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    • 2016
  • On the basis of the energy approach it is reported a development of the yield function and the constitutive equations for the orthotropic material with consideration of the crystal lattice constants and parameters of the crystallographic texture for the general stress state. For practical use in sheet metal forming analysis it is considered different loading scenarios: plane stress and plane strain states. Using the proposed yield function, the influence of single ideal components on the shape of yield surface was analyzed. The six texture components investigated here were cube, Goss, copper, brass, S and rotated cube, as these components are typically observed in rolled sheets from FCC alloys.