• Title/Summary/Keyword: 스트레치 성형

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Aluminum autobody technology for the '90 (90년대의 Al 차체 기술)

  • 박석완;권순용;조원석
    • Journal of the korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.3-8
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    • 1993
  • 본 고에서는 차체제작의 첫단계인 프레스 성형시 문제가 되는 알루미늄 합금판재의 성형성에 대하여 기술한다. 차체용 Al합금판의 성형성을 인장시험, 헤밍시험, 스트레치 포오밍 시험 등으로 조사해 보았다. 냉연강판과 비교하여 현재의 차체용 Al합금판은 강도와 연신율 면에서 열세임에 틀림이 없으나, 앞으로 냉여강판에 버금가는 Al합금판이 나오리라 예상한다. 1. 시편의 종류. 2. 결정립 조직. 3. 집합 조직. 4. 상온 인장시험. 5. 고온 인장시험. 6. 헤밍시험(Hemming test). 7. 스트레치 포오밍 시험(Stretch forming test)

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A Theoretical and Experimental Study on Forming Limits in the Flanging Processes (플랜징 공정 의 성형한계 에 대한 이론 및 실험적 연구)

  • 양동열;박승교
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.6
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    • pp.777-787
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    • 1985
  • The study is concerned with the analysis of flanging as a sheet metal working process. In terms of mechanics, the flanging process can be divided into two groups, i.e, shrink flanging and stretch flanging. In this study, the shrink flanging process is analyzed by using the proposed energy criterion and the forming limit is found for the process. The forming limit for stretch flanging is also found by employing the neckind theory. Experiments are carried out for both processes. Approximate forming limits are obtained from the experiments. An approximate method to calculate the punch force is proposed and the computed results are compared with the experimental results. It is shown that there are good agreements in forming limits and punch forces between theory and experiments.

Flexible Forming Process Analysis for Sheet Material Curved Surface Forming (박판소재 곡면성형을 위한 가변성형공정 해석)

  • Seo, Y.H.;Heo, S.C.;Ku, T.W.;Kim, J.;Kang, B.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.118-121
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    • 2008
  • Flexible die is more efficacious than fixed die which is generally used in stretch forming process in view of production cost. Accordingly, in order to verily the validity of the flexible forming process, curved thin skin structure forming analyses using the fixed and flexible die were performed. As results, merit and demerit with regard to the fixed and flexible die were confirmed. The result of the stretch forming process analysis using the flexible die was better than that using the fixed die in view of the elastic recovery. However wrinkles were occurred on the sheet material due to die cavities between the punches in the flexible forming process, thus the solutions against these problems were presented.

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A Finite Element Analysis of Non-Isothermal Sheet Metal Forming Process (비등온 박판 성형공정의 유한요소해석)

  • ;Wagoner, R. H.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1119-1128
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    • 1990
  • A numerical method for analyzing non-isothermal, rigid-viscoplastic deformation problems has been presented. As an application, a stretch forming of sheet metals, including temperature effect, has been analyzed by a three-dimensional finite element method. Bishop`s step-wise decoupled method is adopted to solve thermomechanical coupling between deformation and heat transfer. Using the method, the effect of temperature on strain distribution during stretch forming is investigated. By comparison of the non-isothermal results with isothermal analysis, the importance of including temperature effects in the analysis of metal forming problems is emphasized. The predicted results were in good agreement with the existing experimental measurements at the different punch temperatures and dome heights investigated. It is also found that any increase of the punch temperature appeared to postpone the strain localization process by lowering the peak strain in the critical punch-sheet contact region and by normalizing strain distribution within the specimen.

Statistical Study on Correlation Between Design Variable and Shape Error in Flexible Stretch Forming (가변스트레치성형 설계변수와 성형오차의 상관관계에 대한 통계적 연구)

  • Seo, Y.H.;Heo, S.C.;Kang, B.S.;Kim, J.
    • Transactions of Materials Processing
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    • v.20 no.2
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    • pp.124-131
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    • 2011
  • A flexible stretch forming process is useful for small quantity batch production because various shape changes of the flexible die can be achieved conveniently. In this study, the design variables, namely, the punch size, curvature radius and elastic pad thickness, were quantitatively evaluated to understand their influence on sheet formability using statistical methods such as the correlation and regression analyses. Forming simulations were designed and conducted by a three-way factorial design to obtain numerical values of a shape error. Linear relationships between the design variables and the shape error resulted from the Pearson correlation analysis. Subsequently, a regression analysis was also conducted between the design variables and the shape error. A regression equation was derived and used in the flexible die design stage to estimate the shape error.

Tendency Analysis of Shape Error According to Forming Parameter in Flexible Stretch Forming Process Using Finite Element Method (유한요소법을 이용한 가변스트레치공정 성형변수에 따른 성형오차 경향분석)

  • Seo, Y.H.;Heo, S.C.;Song, W.J.;Kim, J.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.19 no.8
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    • pp.486-493
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    • 2010
  • A shape error of the sheet metal product made by a flexible stretch forming process is occurred by a various forming parameters. A die used in the flexible stretch forming is composed of a punch array to obtain the various objective surfaces using only one die. But gaps between the punches induce the shape error and the defect such as a scratch. Forming parameters of the punch size and the elastic pad to prevent the surface defect must be considered in the flexible die design process. In this study, tendency analysis of shape error according to the forming parameters in the flexible stretch process is conducted using a finite element method. Three forming parameters, which are the punch size, the objective curvature radius and the elastic pad thickness, are considered. Finite element modeling using the punch height calculation algorithm and the evaluation method of the shape error, which is a representative value for the formability of formed surface, are proposed. Consequently, the shape error is in proportion to the punch size and is out of proportion to the objective curvature radius and the elastic pad thickness.

Identification of Forming Limits of Sheet Metals for Automobile Parts by Asymmetric Deep-drawing Experiments (비대칭 시편의 딥드로잉 실험에 의한 박판금속의 성형한계도)

  • Heo, Hun;Lee, Chung-Ho;Jeong, Jae-Ung
    • Transactions of Materials Processing
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    • v.7 no.1
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    • pp.81-93
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    • 1998
  • Identification of forming limits of sheet metals is an important task to be done before the sheet metal forming processes. The information of the forming limit is indispensable for design of deformed shapes and related forming processes. This procedure becomes more important than ever as the auto-body becomes complicated and the number of auto-body parts is reduced for lower production cost. To identify the forming limit of sheet metals stretching with a hemispherical punch has gained popularity because of the convenient experimental procedure. The stretching experiment however has localized deformation or the shear band is originated from the non-unifrom deformation in the critical circum-stance instead of the absolute criterion. More accurate information of the forming limit therefore could be obtained by a more appropriate experiment to the real process. In this papaer an experiment program is devised to practivally identify the forming limits of sheet metals for auto-body parts. The experiment program contains not only stretching but deep-drawing Both forming experiments use the same hemispherical punch while they use different specimens. Deep-drawing experiments use speci-mens cut out in circular arc on both sides of circular blank to make it torn during the deep-drawing They also use speciments cut out straight in one side of a circular blank to make it deformed unevenly which causes local deformation during the deep-drawing. The experimental result demonstrates that the forming limit diagrams in the two cases show difference in their effective magnitude. The forming limit curve from deep-drawing is located lower than that from stretching. It is noted from the result that the deep-drawing process causes acceleration of localized deformation in comparison with the stretching process. From the experimental result the maximum value of forming limit could be pre-dicted for safe design.

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Usefulness Verification for Flexible Stretch Forming Process using finite Element Method (유한요소법을 이용한 가변 스트레치 성형공정의 적합성 검증)

  • Seo, Y.H.;Heo, S.C.;Park, J.W.;Song, W.J.;Ku, T.W;Kim, J.;Kang, B.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.241-244
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    • 2009
  • This paper deals with a usefulness verification of stretch forming process using flexible die. The stretch forming method is widely used in aircraft and high-speed train industries for manufacturing of skin structure, which is made of sheet metal. A great number of solid dies are originally used and developed for specific shapes with respect to different curvature radii of the skin structures. Accordingly, flexible stretch forming process is proposed in this study. It replaces the conventional solid dies with a set of height adjustable discrete punches. A usefulness of the flexible die is verified through extensive numerical simulations of the stretch forming process for simply curved sheet plate. The elastic recovery is considered and formability evaluations are conducted through a comparison of symmetry plane configurations.

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Development of Stretch Forming Apparatus using Flexible Die (가변금형을 이용한 스트레치 성형장치 개발)

  • Seo, Y.H.;Heo, S.C.;Park, J.W.;Ku, T.W.;Song, W.J.;Kim, J.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.19 no.1
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    • pp.17-24
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    • 2010
  • A stretch forming method has been widely used in sheet metal forming process. Especially, this process has been adopted in aircraft and high-speed train industries for skin structure forming having a variety of curvature. Until now, solid dies, which are designed with respect to the specific shapes and manufactured as a single piece, have been usually applied to stretch forming process. Therefore, a great number of solid dies has to be developed according to the shapes of the curved skin structure. Accordingly, a flexible die is proposed in this study. It replaces the conventional solid dies with a set of height adjustable punch array. A usefulness of the flexible die is verified through a formability comparison with the solid die using finite element method considering an elastic recovery and the stretch forming apparatus with the flexible die is developed.