• Title/Summary/Keyword: Yield Criterion

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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.

TAFEM을 이용한 터널 예제 해석

  • Jo, Seon-Gyu;Jeong, Jae-Dong;Eom, Jong-Uk
    • Proceedings of the Korean Geotechical Society Conference
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    • 1991.10a
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    • pp.216-232
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    • 1991
  • This Finite Element Program(TAFEM) has been developed to be able to carry out the structural analsis of tunnel section and simulate the surrounding ground behaviour due to New Austrian Tunnelling Method, of which main support is the surrounding ground, itself. The Elasto-plastic theory has been applied. The used finite elements are 8-noded isoparametric element(rock & shotcrete), 2 or 3-noded rod element(rock bolt) and infinite boundary element. The load incremental method and tangential stiffness method has been used. Associated flow rule was applied to plastic flow and yield criteria inclued not only Mohr-Coulomb but also Drucker-Prager. In this paper, Drucker-Prager yield criterion has been used. The relationship between plastic strain and stress is based on the incremental strain concept and stress-strain equation on the basis of the stress path of each gauss point has been adopted. It may be rational that rock is considered to be no-tension material, so that no-tension analysis has been adopted in accordance with the brittle fracture constitutive equation.

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Study on the plastic deformation of a cylinder subjected to localized impulsive pressure (국부충격하중을 받는 원관의 삭성변형에 관한 고찰)

  • ;;Zoo, Young Woo
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.5 no.2
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    • pp.131-138
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    • 1981
  • The effect of axial stress on the plastic deformation of rigid-perfectly plastic cylindrical tube under the impulsive band pressure is investigated. It is assumed that the tube is constructed with the material of Tresca's yield criterion. A closed from sloution is obtained for a rectangular pulse shape of uniform band pressure by using the circumscribed yield surface. The analysis shows that the effect ot exial stress is negligible when the dimensionless axial stress(n$\sub$x/= N$\sub$x/.delta.$\sub$y/H) is less than 0.2 or the dimensionless whdth of band pressure(.xi.=C/.root.RH) is greater than 2, but the effect of axial stress is of considerable importance when the axial stress is greater than 0.3 and the width of band pressure is less than 1.

Prediction of forming limits for anisotropic sheet metals with ellipsoidal voids (타원체 보이드를 갖는 이방성 판재의 성형한계 예측)

  • Son, H.S.;Kim, J.;Kim, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.254-257
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    • 2003
  • The modified yield function of Gologanu-Leblond-Devaux in conjunction with the Barlat and Lian's yield criterion is studied to clarify the plastic deformation characteristic of voided anisotropic sheet metals. The void growth of an anisotropic sheet under biaxial tensile loading and damage effect of void growth on forming limits of sheet metals are investigated. Also, the shape parameter defining non-spherical(prolate ellipsoidal) voids with initially random orientations is introduced in M-K model. The predicted forming limits are compared with the published experimental data.

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Kinematics of the Nonsteady Axi-symmetric Ideal Plastic Flow Process

  • Alexandrov, S.;Lee, W.;Chung, K.
    • Fibers and Polymers
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    • v.5 no.3
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    • pp.209-212
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    • 2004
  • A nonsteady axi-symmetric ideal flow solution is obtained here. It is based on the rigid perfect-plastic constitutive law with the Tresca yield condition and its associated flow rule. The process is to deform a circular solid disk into a spherical shell of prescribed geometry. It is assumed that there are no rigid zones and friction stresses. The solution obtained provides the distribution of kinematic variables and involves one undetermined function of the time. This function can be in general found by superimposing an optimality criterion.

Design Sensitivity Analysis of Elasto-perfectly-plastic Structure for Stiffened Shell Structure (탄성-완전-소성 보강쉘 구조물의 설계민감도해석)

  • Jung, Jae-Joon;Lee, Tae-Hee;Lim, Jang-Keun
    • Proceedings of the KSME Conference
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    • 2001.11a
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    • pp.746-752
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    • 2001
  • Design sensitivity analysis for nonlinear structural problems has been emerged in the last decade as a glowing area of engineering research. As a result, theoretical formulations and computational algorithms have already developed for design sensitivity of nonlinear structural problems. There is not enough research for practical nonlinear problems using multi-element, due to difficulties of implementation into FEA. Therefore, nonlinear response analysis for stiffened shell which consists of Mindlin plate and Timoshenko beam, was considered. Specially, it presents the backward-Euler method which is adopted to describe an exact yield state in the stress computation procedure. Then, design sensitivity analysis of nonlinear structures, particularly elasto-perfectly-plastic structure, is developed using direct differentiation method. The accuracy of the developed sensitivity analysis was compared with the central finite difference method. Finally, on the basis of above results, design improvement for stiffened shell is suggested.

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Non-Local Analysis of Forming Limits of Ductile Material Considering Damage Growth (보이드 성장을 고려한 재료의 성형한계에 대한 비 국소 해석)

  • Kim, Young-Suk;Won, Sung-Yeun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.6
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    • pp.914-922
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    • 2003
  • In this paper, the strain localization of voided ductile material has been analyzed by nonlocal plasticity formulation in which the yield strength not only depends on an equivalent plastic strain measure (hardening parameter), but also on the Laplacian thereof. The gradient terms in yield criterion show an important role on modeling strain-softening phenomena of material. The influence of the mesh size on the elastic -plastic deformation behavior and the effect of the characteristic length parameter for localization prediction are also investigated. The proposed nonlocal plasticity shows that the load -strain curves converge to one curve. Results using nonlocal plasticity also exhibit the dependence of mesh size is much less sensitivity than that for a corresponding local plasticity formulation.

Strain Path Dependence of Forming Limits Predicted by Barlat and Lians Non-Quadratic Anisotropic Yield riterion for Sheet Materials

  • Kim, Young-suk;Son, Hyun-sung
    • Journal of Mechanical Science and Technology
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    • v.15 no.2
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    • pp.210-216
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    • 2001
  • This paper presents an analytical study that can predict the path-dependent forming limit of anisotropic sheet materials that experience various combinations of strain paths. To predict the forming limit diagrams(FLD), the proposed analytical procedure is performed within the framework of the Marciniak and Kuczynski(M-K) approach by using the Barlat and Lians non-quadratic anisotropic yield criterion and introducing the effect of the existence of a strain gradient over a stretching punch. The predicted path-dependent forming limit of an anisotropic sheet has been compared with the published experimental results. It has been found that the predicted path-dependent forming limits are in good agreement with the experimental data.

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A Theoretical Investigation of Forming Limits of Voided Anisotropic Sheet Metals (기공을 포함한 이방성 판재의 성형한계 예측)

  • You Bongsun;Yim Changdong;Kim Youngsuk;Won Sungyeun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.8 s.239
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    • pp.1139-1145
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    • 2005
  • Most failures of ductile materials in metal forming processes occurred due to material damage evolution - void nucleation, growth and coalescence. In this paper, the modified yield function of Liao et al in conjunction with the Hosford's yield criterion is studied to clarify the plastic deformation characteristic of voided anisotropic sheet metals. The void growth of an anisotropic sheet under biaxial tensile loading and damage effect of void growth on forming limits of sheet metals are investigated. Also the characteristic length defining the neck geometry is introduced in M-K model to incorporate the effect of triaxial stress in necked region on forming limits. The forming limits theoretically predicted are compared with experimental data. Satisfactory agreement was obtained between the predictions and experimental data.

The Effect of Dynamic Strain Aging on the High Temperature Plastic Deformation Behaviour of Al-Mg Alloy (Al-Mg 합금의 고온 소성 변형 특성에 미치는 동적 변형 시효의 영향)

  • 이상용;이정환
    • Transactions of Materials Processing
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    • v.5 no.4
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    • pp.327-336
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    • 1996
  • The effect of dynamic strain aging on high temperature deformation behaviour of the A-Mg alloy was investigated by strain rate change tests and stress relaxation tests between 20$0^{\circ}C$and 50$0^{\circ}C$. Yield point, short stress transient and periodic discontinuities on the stress-strain curve were considered as an evidence of the effect of dynamic strain aging. With this criterion two distinct strain rate-temperature regimes could be manifested. Dynamic strain aging was considered to be effective in the high temperature-low strain rate regime, whereas dynamic recovery was a dominant deformation mechanism in the low temperature-high strain rate regime. It was found that dynamic strain aging in the high temperature deformation was governed by the mechcanism of diffusion-controlled, viscous dislocation movement.

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