• Title/Summary/Keyword: Hill's Anisotropic Yield Criterion

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The Determination of Initial Blank Shape by Using the One-Step FEM (One-Step FEM을 이용한 초기 블랭크 형상 결정에 관한 연구)

  • Jung, Dong-Won;Lee, Sang-Je
    • Journal of Ocean Engineering and Technology
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    • v.13 no.3 s.33
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    • pp.21-28
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    • 1999
  • In this paper, a finite element method for the determination of initial blank shape in sheet metal forming process will be introduced. The initial blank shape is determined by the only one step from the final to the initial blank. The used finite element inverse method adopted Henky's deformation theory, Hill's anisotropic yield criterion and simplified boundary conditions. Based on this theory. a three-dimensional membrane finite element code was developed. The developed code will be applied to several sheet metal forming examples for the demonstration of its validity.

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Analysis of Deep Drawing of Planar Anisotropic Materials Using the Rigid- Plastic Finite Element Method (강소성 유한요소법을 이용한 평면 이방성 재료의 디프 드로잉 해석)

  • 김형종;김동원
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.2
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    • pp.248-258
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    • 1992
  • Three-dimensional rigid-plastic finite element formulation based on the membrane theory was described and a computer program for large deformation analysis was developed. In the formulation, normal and planar anisotropy of sheet material and rotation of the principal axes of anisotropy was taken into consideration. Sheet metal was assumed to be rigid-plastic material obeying Hill's quadratic yield criterion and its associated flow rule. Deep drawing process, as a preliminary test, for normal anisotropic material was analyzed in order to examine the validity of developed finite element program. The results were consistent with the existing finite element solutions or experimental data. The present study was mainly concerned with the influence of planar anisotropy on deformation behaviour. Finite element analysis and experiment were carried out for the whole process of deep drawing of planar anisotropic material. The computational and experimental results on the shape of ear, strain distribution and punch load were in good agreement.

ESTIMATION OF DUCTILE FRACTURE BEHAVIOR INCORPORATING MATERIAL ANISOTROPY

  • Choi, Shin-Beom;Lee, Dock-Jin;Jeong, Jae-Uk;Chang, Yoon-Suk;Kim, Min-Chul;Lee, Bong-Sang
    • Nuclear Engineering and Technology
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    • v.44 no.7
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    • pp.791-798
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    • 2012
  • Since standardized fracture test specimens cannot be easily extracted from in-service components, several alternative fracture toughness test methods have been proposed to characterize the deformation and fracture resistance of materials. One of the more promising alternatives is the local approach employing the SP(Small Punch) testing technique. However, this process has several limitations such as a lack of anisotropic yield potential and tediousness in the damage parameter calibration process. The present paper investigates estimation of ductile fracture resistance(J-R) curve by FE(Finite Element) analyses using an anisotropic damage model and enhanced calibration procedure. In this context, specific tensile tests to quantify plastic strain ratios were carried out and SP test data were obtained from the previous research. Also, damage parameters constituting the Gurson-Tvergaard-Needleman model in conjunction with Hill's 48 yield criterion were calibrated for a typical nuclear reactor material through a genetic algorithm. Finally, the J-R curve of a standard compact tension specimen was predicted by further detailed FE analyses employing the calibrated damage parameters. It showed a lower fracture resistance of the specimen material than that based on the isotropic yield criterion. Therefore, a more realistic J-R curve of a reactor material can be obtained effectively from the proposed methodology by taking into account a reduced load-carrying capacity due to anisotropy.

Axisymmetric Multi-Stage Deep Drawing Die Design Analysis Using Finite Element Method (유한요소법을 이용한 축대칭 다단계 딥드로잉 금형 설계 해석)

  • Lee, Dong-Ho;Lee, Seung-Yeol;Geum, Yeong-Tak
    • Transactions of Materials Processing
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    • v.7 no.6
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    • pp.594-602
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    • 1998
  • The design analysis of axisymmetric, multi-stage deep drawing dies was performed using the rigid-viscoplastic finite element formulation. In the formulation the axisymmetric CFS algorithm was employed. Hill's non-quadratic normal anisotropic yield criterion and isotropic hardening rule were considered. For trial initial displacements and tool contact points. the geometric force equilibrium method was adopted. In order to see the validity of the formulation, the multi-stage deep drawing processes of shell-cylinder front part of hydraulic booster were simulated. The simulation showed good agreements with measurments and PAM-STAMP results.

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Forming Limit Diagrams of Zircaloy-4 and Zirlo Sheets for Stamping of Spacer Grids of Nuclear Fuel Rods (핵연료 지지격자 성형을 위한 Zircaloy-4와 Zirlo 판재의 성형한계도 예측)

  • Seo, Yun-Mi;Hyun, Hong-Chul;Lee, Hyung-Yil;Kim, Nak-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.8
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    • pp.889-897
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    • 2011
  • In this work, we investigated the theoretical forming limit models for Zircaloy-4 and Zirlo used for spacer grid of nuclear fuel rods. Tensile and anisotropy tests were performed to obtain stress-strain curves and anisotropic coefficients. The experimental forming limit diagrams (FLD) for two materials were obtained by dome stretching tests following NUMISHEET 96. Theoretical FLD depends on FL models and yield criteria. To obtain the right hand side (RHS) of FLD, we applied the FL models (Swift's diffuse necking, M-K theory, S-R vertex theory) to Zircaloy-4 and Zirlo sheets. Hill's local necking theory was adopted for the left hand side (LHS) of FLD. To consider the anisotropy of sheets, the yield criteria of Hill and Hosford were applied. Comparing the predicted curves with the experimental data, we found that the RHS of FLD for Zircaloy-4 can be described by the Swift model (with the Hill's criterion), while the LHS of the FLD can be explained by Hill model. The FLD for Zirlo can be explained by the S-R model and the Hosford's criterion (a = 8).

Axisymmetric Multi-Stage Deep Drawing Dies Design Analysis Using Finite Element Method (유한요소법을 이용한 축대칭 다단계 딥드로잉 금형 설계 해석)

  • 이동호;금영탁
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1998.06a
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    • pp.65-73
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    • 1998
  • The design analysis of axisymmetric, multi-stage deep drawing dies was performed using the rigid-viscoplastic finite element formulation. In the formulation, the axisymmetric CFS algorithm was employed. Hill's non-quadratic normal anisotropic yield criterion and isotropic hardening rule were considered. For trial initial displacements and tool contact points, the geometric force equilibrium method was adopted. In order to see the validity of the formulation, the multi-stage deep drawing processes of shell-cylinder front part of hydraulic booster were simulated. The simulation showed good agreements with measurements and PAM-STAMP.