• Title/Summary/Keyword: Flexible Stretch Forming

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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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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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Manufacture of Architectural Skin-structure with a Double Curved Surface Using Flexible Stretch Forming (가변 스트레치 성형공정을 활용한 건축외피 구조물의 비정형 곡면 제작)

  • Park, J.W.;Kim, Y.B.;Kim, J.;Kim, K.H.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.22 no.4
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    • pp.196-203
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    • 2013
  • Flexible stretch forming is an appropriate process for manufacturing of components for aerospace, shipbuilding and architecture structures. Flexible stretch forming has several advantages including that it could be applied to form various shapes such as ones with double curved surfaces. In this study, a systematic numerical simulation was conducted for forming double curved surfaces using flexible stretch forming. The desired surface had a saddle type configuration. It had two radii one of 2500mm and the other of 2000mm along its length and width. In the simulation, the decrease of elastic recovery due to the stretching was confirmed. Experiments were also conducted to confirm the viability of the process. By comparing the simulation to the experiment results, the suitability of flexible stretch forming for double curved surfaces was verified. From the results, the maximum error from desired surface was confirmed at about 1.3mm at the edge of the surface. Hence, it is confirmed that flexible stretch forming has the capability and feasibility to manufacture curved surfaces for architectural skin-structures of buildings.

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.

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.

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.

Design of Flexible Die Punch and Control System for Three-dimensional Curved Forming Surface (3차원 성형곡면 구현을 위한 가변금형의 펀치 및 제어시스템 설계)

  • Seo, Y.H.;Heo, S.C.;Ku, T.W.;Kim, J.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.20 no.3
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    • pp.206-213
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    • 2011
  • A flexible die, which is composed of a number of punches with adjusted heights to form a three-dimensional curved surface, is a crucial part of a flexible forming technology. In this study, the punch and control system of the flexible die were designed. The flexible die is divided into three modules, namely, punch, control and joint, and the corresponding modules were developed. The punch module materializes a three-dimensional forming surface by the control module, which is composed of an AC servo motor set and a linear guide. The joint module is necessary for the sequential motion between the servo motor set and the punch module. A sequential motion algorithm for the AC servo motor set, that uses the data of the punch relative heights, was also proposed. Finally, a flexible stretch forming test was carried out using the presently designed flexible die.

Multi Point Press Stretch Forming System Applied to Curved Hull Plate of Aluminum Ship (알루미늄 선박의 외판 가공을 위한 인장성형 시스템 연구)

  • Bae, Chul-Nam;Hwang, Se-Yun;Lee, Jang-Hyun;Jeong, Uh-Cheul;Kim, Kwang-Ho
    • Korean Journal of Computational Design and Engineering
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    • v.17 no.3
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    • pp.188-197
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    • 2012
  • Recently, aluminum ships are constructed more than ever because of the environmental pollution generated by FRP (Fiber Reinforced Plastic) ships. In particular, FRP ships have been replaced by the Aluminum ships. The forming process of the curved aluminum plate has been performed only by labor works without systematic technique. Therefore, it is difficult to construct the aluminum ship that the design satisfies both required propulsion performance and hull design. Present study introduces a MPSF (Multi Point Stretching Forming) that is a flexible manufacturing technique to form large sheet panels of doubly curvature. The hull pieces are stretch-formed over the MPSD (multi-point stretching die) generated by the punch element matrix. In this study, MPSF is applied to deform the doubly curved surfaces of aluminum ship. The forming system including FEA (finite element analysis) of the processes for stretching the plate were carried out by static implicit analysis is suggested. Residual deformation of the surface is modeled by an elasto-plastic contact phenomena while the forming process is simulated by FEA. Finally, the proposed system is also validated, comparing the deformed shape by MPSF with that of object surfaces.

Development of a Flexibly-reconfigurable Roll Forming Apparatus for Curved Surface Forming (곡면성형을 위한 비정형롤판재성형 장비 개발)

  • Yoon, J.S.;Park, J.W.;Son, S.E.;Kim, H.H.;Kim, J.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.25 no.3
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    • pp.161-168
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    • 2016
  • Sheet metals are often required to be formed into three dimensional curved shapes for use as skin structures. As a result various sheet metal forming methods, such as press die forming, stretch forming, and line heating have been used over the years in industrial production lines. Although they are extensively used in industry, these methods are not suitable for small quantity batch productions. Studies have been conducted to improve or replace these methods with plausible flexible forming technologies. As a part of these studies, we developed a new and more efficient forming device named flexibly-reconfigurable roll forming (FRRF). The current study presents the process development and experimental verification for the applicability of this device. To improve the efficiency of the FRRF apparatus, several hardware components were invented and a suitable operating program was developed using MFC of visual C++. The ways to make the FRRF apparatus fully functional are also described. Sheet metal was formed into three dimensional shapes using the FRRF apparatus and the final products are presented as evidence for the applicability of the developed device.

Press Forming of Extruded Aluminum Profile for Automotive Parts (자동차 부품용 알루미늄 압출재의 프레스 성형기술)

  • Choi Young;Park Joon-Hong;Kang Myun-Gyu;Oh Kae-Hee;Park Sang-Woo;Yeo Hong-Tae
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.5 s.182
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    • pp.51-58
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    • 2006
  • The necessities for heightening fuel efficiency as well as lightweight design, lead to an increase of the use of aluminum alloys in the automobile industry. Extruded aluminum profile channels are used widely for the design of frame parts as lightweight assemblies, especially if a high stiffness is needed. While many applications can be realized with forming of hollow square-sectioned extruded profiles such as a stretch bending and a hydro-forming, some applications demand the use of a press bending which can be hardly found in the previous study. In this study, by introducing the use of a press bending into car sub-frames, the demands for higher accuracy as well as higher flexible method than the conventional methods will be satisfied. With respect to the design of sub-frames, the process planning was performed from the shape of a sub-frame product. The designed processes were analyzed by the commercial FEM code, DEFORM-3D. Forming dies for the each process were designed and prototypes of sub-frames were manufactured by the verified farming process. In addition, some of the important features of design parameters in the press bending were reviewed.