• Title/Summary/Keyword: Rigid-Viscoplastic FEM

Search Result 22, Processing Time 0.028 seconds

Implementation of Polycrystal Model in Rigid Plastic Finite Element Method (강소성 유한요소법에서의 다결정 모델의 구현)

  • Kang, G.P.;Lee, K.;Kim, Y.H.;Shin, K.S.
    • Transactions of Materials Processing
    • /
    • v.26 no.5
    • /
    • pp.286-292
    • /
    • 2017
  • Magnesium alloy shows strong anisotropy and asymmetric behavior in tension and compression curve, especially at room temperature. These characteristics limit the application of finite element method (FEM) which is based on conventional continuum mechanics. To accurately predict the material behavior of magnesium alloy at microstructural level, a methodology of fully coupled multiscale simulation is presented and a crystal plasticity model as a constitutive equation in the simulation of metal forming process is introduced in this study. The existing constitutive equation for rigid plastic FEM is modified to accommodate deviatoric stress component and its derivatives with respect to strain rate components. Viscoplastic self-consistent (VPSC) polycrystal model was selected as a constitutive model because it was regarded as the most robust model compared to Taylor model or Sachs model. Stiffness matrix and load vector were derived based on the new approach and implemented into $DEFORM^{TM}-3D$ via a user subroutine handling stiffness matrix at an elemental level. The application to extrusion and rolling process of pure magnesium is presented in this study to assess the validity of the proposed multiscale process.

Plane Strain Analysis of Thin Sheet Forming with Arbitrary Conditions (임의 조건으로 성형되는 박판의 평면변형률 해석)

  • ;;R. H. Wagoner
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1992.03a
    • /
    • pp.201-212
    • /
    • 1992
  • The plane strain analysis for simulating the stretch/draw forming operation of arbitrarily-shaped tool profiles and arbitrarily draw-in conditions is introduced. An implicit, incremental, updated Lagrangian formulation is employed, introducing a rigid-viscoplastic constitutive equation. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshe without depending on the explicit spatial derivatives of tool surfaces. The FEM formulation is tested in the sections automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains in the stretched section is obtained, but also the numerical stability of current formulation is verified in the two-side draw-in section.

  • PDF

Prediction of Earings in the Deep Drawing Processes of a Cylindrical Cup (원통컵 디프드로잉 공정의 귀발생 예측)

  • 이승열;이승열;금영탁;정관수;박진무
    • Transactions of Materials Processing
    • /
    • v.4 no.3
    • /
    • pp.222-232
    • /
    • 1995
  • The planar anisotripic FEM analysis for predicting earing profiles and draw-in amounts in the deep-drawing process is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-based unit vector and normal contact pressure. The consistent full set of governing relations, which is comprising euilbrium and geometric constraint equations, is appropriately linearized. Barlat's strain-rate potential is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and potential parameters. The linear triangular membrane elements are used for depicting the formed sheet. In the numerical simulations of deep drawing processes of a flat-top cylindrical cup for 2090-T3 aluminum alloy sheet show good agreement with experiments, although some discrepancies were observed in the directional trend of cup height and thickness strains.

  • PDF

Design of automotive inner panel by sectional forming analysis (단면성형 해석에 의한 자동차 내부 판넬의 설계)

  • 금영탁;왕노만
    • Journal of the korean Society of Automotive Engineers
    • /
    • v.12 no.6
    • /
    • pp.48-59
    • /
    • 1990
  • A finite element program was developed using line elements for simulating the stretch/draw forming operation of an arbitrarily-shaped plane-strain section. An implicit, incremental, updated Lagrangian formulation is employed, introducing a minimum plastic work path assumption for each time step. Geometric and material nonlinearities are also considered within each time step. The finite element equation is based on the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The membrane approximation is adopted under the plane stress assumption. The sheet material is assumed to obey a rigid-viscoplastic constitutive law. The developed program was tested in the die-tryout of typical automotive inner panels. In order to determine a single friction coefficient and boundary length, FEM results and measurements of thinning for a stretched section of final die were compared. After finding analysis parameters, the sheet forming operations of original and final die designs were simulated. Excellent agreement between measured and computed thickness strains was obtained and the developed program was able to identify die designs which were rejected during die tryout.

  • PDF

A Study On The Microstructural Evolution In Hot Rolling (열간압연중 발생하는 미세조직 변화에 관한 연구)

  • 조현중;김낙수
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1995.10a
    • /
    • pp.16-29
    • /
    • 1995
  • A full three-dimensional thermo-coupled rigid-viscoplastic finite element method and the currently developed microstructural evolution system which includes semi-empirical mathematical equations suggested by different research groups were used together to form an integrated system of process and microstructure simulation of hot rolling. The distribution and time history of thermomechanical variables such as temperature, strain, strain rate, and time during pass and between passes were obtained FEM analysis of multipass hot rolling processes. Then distribution of metallurgical variables were calculated successfully on the basis of instantaneous thermomechanical data. For the verification of this method the evolution of microstructure in plate rolling and shape rolling was simulated and their results were compared with the data available in literature. Consequently, this approach makes it passible to describe the realistic evolution of microstructure by avoiding the use of erroneous average value and can be used in CAE of multipass hot rolling.

  • PDF

A Study of Forging Equipment for One Body Crankshaft of Medium Sized Marine Engine (선박 중형엔진 일체형 Crankshaft 제작용 형단조장치 기술개발에 관한 연구)

  • 윤성만
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1999.03b
    • /
    • pp.107-110
    • /
    • 1999
  • The purpose of this research is for the development of a new type forging equipment H.C.G(Hyundai Continuous Grain-flow) by using two virtual build-up tools rigid viscoplastic FEM and downsized plasticine experiment. This forging equipment consists of consecutive horizontal and vertical pressure while the traditional forging method consists of only vertical pressure. Using this method high quality crankshafts can be forged as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape die reaction forces stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results the proper design of the H.C.G for ging equipment is enabled.

  • PDF

Sectonal Forming Analysis of Stamping Processes of Aluminum Alloy Sheet Metals (알루미늄 합금 박판 스탬핑 공정의 단면 성형 해석)

  • 이광병;이승열;금영탁
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1996.10a
    • /
    • pp.38-47
    • /
    • 1996
  • Sectional analysis program for plane strain or axisymmetric geometry of aluminum alloy sheet metals was developed. For modeling the anomalous behavior of aluminum alloy, Barlat's strain rate potential and Hill's 1990 non-quadratic yield theory arranged under the plane stress assumption were employed. 2-D rigid-viscoplastic FEM formulation based on the bending-augmented membrane theory was derived, solving simultaneously force equilibrium as well as non-penetration condition. Isotropic hardening law was also assumed for yielding behavior. To verify the validity and availability of the developed program, 2-D stretch/draw forming process for plane strain geometry and cylindrical cup deep drawing process for axisymmetric geometry were simulated.

  • PDF

Analysis of Microstructures in a Forged Ti-6Al-4V Disk (Ti-6Al-4V 단조 디스크의 미세조직 분석)

  • 김대영;박종진
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1997.10a
    • /
    • pp.202-209
    • /
    • 1997
  • The mechanical properties of Ti-6Al-4V greatly vary for changes of microstructures. Therefore, when manufacturing components with this material, it is important to understand the influence of process parameters to the resulting microstructures. In the present investgation, it was attempted to relate the process parameters with the microstructures in a hot forged Ti-6Al-4V disk. The investigation was carried out by a rigid thermo-viscoplastic FEM analysis, flow stress measurements and microstructure studies. It was found that the dynamic recrystallization would hardly occur in this material and that variations of strain, strain rate and temperature of several locations in the disk were below the assumed dynamic recrystallization zone. These findings confirmed the experimental obervations that the microstructures in the disk were only deformed without being recrystallized.

  • PDF

A Study of Forging Equipment for One Body Crankshaft of Medium Sized Marine Engine (선박 중형엔진용 일체형 Crankshaft 단조장치에 관한 연구)

  • 박승희;윤성만;신상엽;박래원;박종국;이응기;김대두
    • Transactions of Materials Processing
    • /
    • v.8 no.3
    • /
    • pp.237-244
    • /
    • 1999
  • The purpose of this research is for the development of a new type forging equipment. H.C.G.(Hyundai Continuous Grain-Flow), by using two virtual build-up tools, rigid viscoplastic FEM and downsized plasticine experiment. This forging method consists of only vertical pressuree. Therefore, high quality crankshafts can be forged with this method as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape, die reaction forces, stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results, the proper design of the H.C.G. forging equipment is enabled.

  • PDF

Earing Predictions in the Deep-Drawing Process of Planar Anisotropic Sheet-Metal (평면 이방성 박판 딥드로잉 공정의 귀발생 예측)

  • 이승열;금영탁;정관수;박진무
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1994.03a
    • /
    • pp.118-128
    • /
    • 1994
  • The planar anisotropic FEM analysis for predicting the earing profiles and draw-in amounts in the deep-drawing processes is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-based unit vectors and the normal contact pressure. the consistent full set of governing relations, comprising equilibrium and geometric constraint equations, is appropriately linearized. Barlat's strain-rate potential is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and potential parameter. The linear triangular membrane elements are used for depicting the formed sheet. with the numerical simulations of deep drawing processes of flat-top cylindrical cup for the 2090-T3 aluminum effects on the earing behavior are examined. Earing predictions made for the 2090-T3 aluminum alloy sheet show good agreement with experiments, although some discrepancies were observed in the directional trend of cup height and thickness strains.

  • PDF