• Title/Summary/Keyword: 판재 굽힘 가공

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Forming Analysis of L-type Bending of Sandwich Sheet with Pyramid Core (피라미드 코어를 가진 샌드위치 판재의 L형 굽힘 성형해석)

  • Lim, Sung-Jin;Chung, Wan-Jin;Kim, Jong-Ho
    • Elastomers and Composites
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    • v.44 no.4
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    • pp.378-383
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    • 2009
  • In this study, the use of a condensed model is proposed for the simulation of forming of sandwich sheet with pyramid core. A corresponding finite element analysis for L-type bending is carried out to prove the accuracy and the effectiveness. In order to improve the accuracy of forming analysis, more precise modeling of core shape and consideration of work-hardening of previous core forming are carried out. Simulation results are compared with those of experiment. Deformation shape and post-buckling behavior by simulation are in good agreement with those of experiment for the considerable range of deformation. From the comparison of force-displacement curve, it is shown that the proposed model shows good prediction of post-buckling behavior.

Evaluation of incremental sheet forming characteristics for 3D-structured aluminum sheet - part 2 (3D 구조 알루미늄 판재의 점진판재성형 특성 평가 (제2보))

  • Kim, Young-Suk;Do, Van-Cuong;Ahn, Dae-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.3
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    • pp.1585-1593
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    • 2015
  • 3D-structured (embossed) aluminum sheets have been used in the heat insulation purpose for automative exhaust parts because of increasing their surface areas and stiffness reinforcement imposed in making the embossing pattern. However, there are many restrictions in press forming of the embossed sheet compared with the flat sheet (non-embossed one) because of its difference in the mechanical properties and the geometrical 3-dimensional shape. In this paper we investigated the deformation characteristic of embossed aluminum sheet in the incremental sheet forming process which has frequently used in the design verification and the trial manufacturing of sheet products. The single point incremental forming (SPIF) experiments for the rectangular cone forming using the CNC machine with a chemical wood-machined die and a circular tool shape showed that the formability of the embossed sheet are better than that of the flat sheet in view of the maximum angle of cone forming. This comes from the fact that the embossed sheet between the tool and the elastic die wall is plastically compressed and the flatted area contributes to increase the plastic deformation. Also the tool path along the outward movement from the center showed a better formability than that of the inward movement from the edge. However the surface quality for the tool path along the outward movement evaluated from the surface deflection is inferior than that of the tool path along the inward movement.

Deformation Pattern of the Pyramid-Core Welded Sandwich Sheet Metal in L-Bending (피라미드코어재를 갖는 접합판재의 L-굽힘가공 특성)

  • Kim, J.H.;Chung, W.J.;Cho, Y.J.;Kim, H.G.;Hong, M.J.;Yooe, J.S.;Seong, D.Y.;Yang, D.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.316-319
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    • 2008
  • The L-bending of inner-structure bonded sandwich sheet metal is examined by using a bending die attached to the material testing machine. The specimen is composed of top and bottom layers and a middle layer of pyramid-core structure and each layer is bonded by brazing. The variables chosen for experiments were clearance between punch and die, location of bend line on the specimen surface and clamping type of specimen during L-bending. Effects of these variables on deformation of specimen around die-corner radius were investigated. It was shown that the irregular shapes of recess are formed in the inner layer of bended parts and they greatly depend on working conditions.

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Experimental estimation of effective strain on strength of hydroformed engine cradle (액압성형공정을 적용한 엔진크레들의 변형률에 따른 강도변화의 실험적 연구)

  • Lee, S.M.;Park, H.K.;Yim, H.S.;Kim, K.S.;Moon, Y.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.503-506
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    • 2008
  • 본 연구에서는 하이드로포밍 공정을 적용한 엔진크레들 제품에 대해 최종 제품의 강도를 평가하고자 하였다. 먼저 적용 판재인 370과 440 소재에 대해 인장시험을 수행하여 소재의 경도와 강도의 상관관계를 분석하여 경도와 강도의 변환식을 도출하였다. 그런 다음 예비굽힘, 예비성형, 최종성형된 제품의 각 공정에 따른 유효변형률을 측정하고 같은 위치에서의 경도를 측정하였다. 측정된 경도는 앞서 도출한 경도와 강도의 변환식에 대입하여 각 공정을 마친 제품의 강도를 예측하고 결국 하이드로포밍된 엔진 크레들 제품의 유효변형률에 따른 강도를 예측식을 실험으로 도출하였다. 그 결과 예비굽힘, 예비성형, 최종성형을 마친 엔진 크레들 제품에 대해 유효변형률이 $24{\sim}72%$로 변하였고 이때 HF370의 경우에는 유동응력값이 $375{\sim}500MPa$로 증가하여 원소재에 비해 성형 후 $25{\sim}66%$의 강도증가량을 보였고, HF440의 경우에는 $470{\sim}565MPa$로 증가하여, 원소재에 비해 $17{\sim}41%$로 강도가 증가하는 것으로 나타났다. 그리고 이와 같은 변화값을 이용하여 유효변형률과 강도의 상관관계를 도출하였다.

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Comparison of Friction Coefficients of Sheet Materials in Various Deformation Modes (변형모드별 판재의 마찰특성 비교)

  • Kim, Young-Suk;Kim, Ki-Soo
    • Transactions of Materials Processing
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    • v.3 no.1
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    • pp.51-62
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    • 1994
  • Cup drawing test and U-bending test were performed to evaluate the friction characteristics of sheet materials for the different deformation modes involved in stamping process. The coefficient of friction calculated from the each test was compared to that obtained from the draw bead friction test. It was clarified that the cup drawing test could be simply used for evaluating the friction characteristic of sheet material in deep drawing process with high contacting pressure. However the U-bending test is suitable to evaluate the frictional characteristic of sheet material in bending process with low contacting pressure.

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Sectional Finite Element Analysis of Forming Process of Aluminum Sandwich Sheet by Bending Augmented Membrane Elements (굽힘 첨가 박막요소에 의한 알루미늄 샌드위치 판재 성형공정의 단면 유한요소 해석)

  • 이재경;금영탁;유용문;이명호
    • Transactions of Materials Processing
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    • v.10 no.2
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    • pp.91-100
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    • 2001
  • A sectional FEA program is developed lot analyzing forming processes of sandwich sheets, which are intensively used recently as a lightweight material of an automobile body. The aluminum sandwich sheet consists of two aluminum skins and a polyprophylen core in between. The aluminum sandwich sheet is dominantly effected by the bending effects in small radius of curvature, so that an appropriate description of bending effects is required to analyze the forming processes. For the evaluation of bending effects, the bending equivalent forces are calculated from the bending moment computed using the curvature of the tool and are added to the membrane stretch forces. To verify the validity of the developed program the sectional FEA results in stretch/draw forming Processes of a square cup and draw forming Processes of an outer hood panel were compared with the measurements.

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The Development of Inner Structure of Metallic Sandwich Plates for Bending (굽힘성형을 위한 금속 샌드위치판재의 내부구조재 개발)

  • Seong, D.Y.;Jung, C.G.;Yoon, S.J.;Shim, D.S.;Lee, S.H.;Ahn, D.G.;Yang, D.Y.
    • Transactions of Materials Processing
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    • v.15 no.2 s.83
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    • pp.126-131
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    • 2006
  • Metallic sandwich plates are ultra-light materials not only with high strength and stiffness but also with other multifunctional physical properties. Inner dimpled shell structure can be fabricated by a piecewise sectional forming process, and then bonded with face sheets of the same material by resistance welding. Possible region for bending and limit radius of curvature are defined to compare the formability of sandwich plates. Tests have shown that sandwich plates with inner dimpled shell structure subject to bending have longer possible region for bending and smaller limit radius of curvature than other types of sandwich plates. The proposed inner dimpled shell structure is shown to have better formability of sandwich plates for bending than other types inner structures.

Efficient FE-Analysis Method with Equivalent Models for Metallic Sandwich Plates with Inner Dimpled Shell Subject to 3-Point Bending (등가 모델을 이용한 3점 굽힘 하중을 받는 딤플형 금속 샌드위치판재의 효율적 해석)

  • Seong D. Y.;Jung C. G.;Yoon S. J.;Yang D. Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.05a
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    • pp.130-133
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    • 2005
  • Efficient finite element method has been introduced for metallic sandwich plates subject to 3-point bending. A full model 3-point bending FE-analysis shows that plastic behavior of inner structures appears only at the load point. So, Unit structures of sandwich plates are defined to numerically calculate the bending stiffness with recurrent boundary condition of pure bending. And then equivalent models with same bending stiffness and strength of full models are designed analytically. It is demonstrated that results of both models are almost same and FE analysis method with equivalent models can reduce analysis time effectively.

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Forming Analysis of L-type Bending of Sandwich Sheet with Pyramid Core (피라미드 코어를 가진 샌드위치 판재의 L형 굽힘 성형해석)

  • Chung, W.J.;Kim, J.H.;Lim, S.J.;Yoo, J.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.560-563
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    • 2008
  • A condensed model is proposed for the simulation of forming of sandwich sheet with pyramid core. A corresponding finite element analysis for L-type bending is carried out to prove the accuracy and the effectiveness. Simulation results are compared with those of experiment. Deformation shape and post-buckling behavior by simulation are in good agreement with those of experiment for the considerable range of deformation. From the comparison of force-displacement curve, it is shown that the proposed model shows good prediction of the forming force compared to the experiment. Thus, the effectiveness of the proposed method is sufficiently demonstrated.

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Efficient Methods of Prediction Incorporating Equivalent Models for Elasto-Plastic Bending Behavior of Metallic Sandwich Plates with Inner Dimpled Shell Structure (등가형상을 이용한 딤플형 금속 샌드위치 판재의 효율적 굽힘 거동 예측)

  • Seong D. Y.;Jung C. G.;Yoon S. J.;Yang D. Y.
    • Transactions of Materials Processing
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    • v.14 no.8 s.80
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    • pp.718-724
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    • 2005
  • An efficient finite element method has been introduced for analysis of metallic sandwich plates subject to bending moment. A full model 3-point bending FE-analysis shows that the plastic behavior of inner structures appears only at the load point. The unit structures of sandwich plates are defined to numerically calculate the bending stiffness and strength utilizing the recurrent boundary condition for pure bending analysis. The equivalent models with the same bending stiffness and strength of full models are then designed analytically. It is demonstrated that the results of both models are almost the same and the FE-analysis method incorporating the equivalent models can reduce the computation time effectively. The dominant collapse modes are face buckling and face yielding. Since the inner dimpled structures prevent face buckling, sandwich plates with inner dimpled shell structure can absorb more energy than other types of sandwich plates during the bending behavior.