• Title/Summary/Keyword: Phase-field model

Search Result 558, Processing Time 0.03 seconds

Phase Field Modeling of Graphitization in Ductile Cast Iron by Strip Casting(I);Modeling of Phases with Negligible Solubility (스트립캐스팅한 구상흑연주철 박판의 흑연화 과정에 대한 phase-field 모델링 (I);고용도가 없는 상의 모델링)

  • Kim, Sung-Gyun;Ra, Hyung-Yong
    • Journal of Korea Foundry Society
    • /
    • v.20 no.2
    • /
    • pp.129-140
    • /
    • 2000
  • This study aims at the phase-field modeling of the phase transformation in graphitization of the cast iron. As the first step, we constructed a phase-field model including the phases with negligible solubility. Under the dilute regular solution approximation, a simplified version of the phase-field model was obtained, which can be used for the phase transformation related with the stoichiometric phases. The results from the numerical calculation of the phase-field model was in good agreement with the exact analytic solution. The compositional shift due to Gibbs-Thomson effect can be reproduced within 0.5% error in the numerical calculation. The interface velocity, whereas, in numerical calculation of phase-field model appeared to be 15% larger than that from the analytic solution. This error is due to the shift of the interface position in phase-field model from the position with ${\phi}=0.5$.

  • PDF

Nondestructive Evaluation of Railway Bridge by System Identification Using Field Vibration Measurement

  • Ho, Duc-Duy;Hong, Dong-Soo;Kim, Jeong-Tae
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.30 no.6
    • /
    • pp.527-538
    • /
    • 2010
  • This paper presents a nondestructive evaluation approach for system identification (SID) of real railway bridges using field vibration test results. First, a multi-phase SID scheme designed on the basis of eigenvalue sensitivity concept is presented. Next, the proposed multi-phase approach is evaluated from field vibration tests on a real railway bridge (Wondongcheon bridge) located in Yangsan, Korea. On the steel girder bridge, a few natural frequencies and mode shapes are experimentally measured under the ambient vibration condition. The corresponding modal parameters are numerically calculated from a three-dimensional finite element (FE) model established for the target bridge. Eigenvalue sensitivities are analyzed for potential model-updating parameters of the FE model. Then, structural subsystems are identified phase-by-phase using the proposed model-updating procedure. Based on model-updating results, a baseline model and a nondestructive evaluation of test bridge are identified.

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF A PHASE-FIELD MODEL FOR ANISOTROPIC INTERFACIAL ENERGY

  • Kim, Jun-Seok
    • Communications of the Korean Mathematical Society
    • /
    • v.22 no.3
    • /
    • pp.453-464
    • /
    • 2007
  • A computationally efficient numerical scheme is presented for the phase-field model of two-phase systems for anisotropic interfacial energy. The scheme is solved by using a nonlinear multigrid method. When the coefficient for the anisotropic interfacial energy is sufficiently high, the interface of the system shows corners or missing crystallographic orientations. Numerical simulations with high and low anisotropic coefficients show excellent agreement with exact equilibrium shapes. We also present spinodal decomposition, which shows the robustness of the pro-posed scheme.

Numerical Calculation of Transformation Plasticity Using a FE Analysis Coupled with n Phase Field Model (상장모델과 유한요소법의 연계해석을 통한 변태소성 전산모사)

  • Cho, Y.G.;Kim, J.Y.;Cha, P.R.;Lee, J.K.;Han, H.N.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2009.05a
    • /
    • pp.318-321
    • /
    • 2009
  • Transformation plasticity is that when a phase transformation of ferrous or non-ferrous alloys progresses even under an extremely small applied stress compared with a yield stress of the material, a permanent deformation occurs. One of widely accepted description for the transformation was proposed by Greenwood and Johnson [1]. Their description is based on an assumption that a weaker phase of an ideal plastic material could deform plastically to accommodate the externally applied stress and the internal stress caused by the volumetric change accompanying the phase transformation. In this study, an implicit finite element model was developed to simulate the deformation behavior of a low carbon steel during phase transformation. The finite element model was coupled with a phase field model, which could simulate the kinetics for ferrite to austenite transformation of the steel. The thermo-elasto-plastic constitutive equation for each phase was adopted to confirm the weaker phase yielding, which was proposed by Greenwood and Johnson [1]. From the simulation, the origin of the transformation plasticity was quantitatively discussed comparing with the other descriptions of it.

  • PDF

Three-phase-lag model on a micropolar magneto-thermoelastic medium with voids

  • Alharbi, Amnah M.;Othman, Mohamed I.A.;Al-Autabi, Al-Anoud M. Kh.
    • Structural Engineering and Mechanics
    • /
    • v.78 no.2
    • /
    • pp.187-197
    • /
    • 2021
  • This paper harnesses a micropolar thermoelastic medium consisting of voids to scrutinize the impacts of a magnetic field on it. To assess the problem, the three-phase-lag model (3PHL) has been employed and the analytical expressions of various variables under consideration have been derived using normal model analysis. The paper presents a graphical illustration of the material's stress, temperature, and dimensionless displacement. It has also been ensured that the predictions associated with results by different theories are not neglected instead; they are used to carry out appropriate comparisons in scenarios where the magnetic field is present as well as absent. The numerical results indicate that the magnetic field and the phase-lag of heat flux play a vital role in determining the distribution of field quantities. Thus, the investigation helped derive various interesting cases.

PHASE FIELD MODELING OF CRYSTAL GROWTH

  • Sekerka, Robert F.
    • Proceedings of the Korea Association of Crystal Growth Conference
    • /
    • 1996.06a
    • /
    • pp.139-156
    • /
    • 1996
  • The phase field model is becoming the model of choice for the theoretical study of the morphologies of crystals growth from the melt. This model provides an alternative approach to the solution of the classical (sharp interface) model of solidification by introducing a new variable, the phase field, Ø, to identify the phase. The variable Ø takes on constant values in the bulk phases and makes a continuous transition between these values over a thin transition layer that plays the role of the classically sharp interface. This results in Ø being governed by a new partial differential equation(in addition to the PDE's that govern the classical fields, such as temperature and composition) that guarantees (in the asymptotic limit of a suitably thin transition layer) that the appropriate boundary conditions at the crystal-melt interface are satisfied. Thus, one can proceed to solve coupled PDE's without the necessity of explicitly tracking the interface (free boundary) that would be necessary to solve the classical (sharp interface) model. Recent advances in supercomputing and algorithms now enable generation of interesting and valuable results that display most of the fundamental solidification phenomena and processes that are observed experimentally. These include morphological instability, solute trapping, cellular growth, dendritic growth (with anisotropic sidebranching, tip splitting, and coupling to periodic forcing), coarsening, recalescence, eutectic growth, faceting, and texture development. This talk will focus on the fundamental basis of the phase field model in terms of irreversible thermodynamics as well as it computational limitations and prognosis for future improvement. This work is supported by the National Science Foundation under grant DMR 9211276

  • PDF

Study of Li-Ion Diffusion and Phase Transition in Cathode of Li-Ion Battery (리튬 이차전지의 양극 내부 이온 확산 및 상변화 특성 연구)

  • Kim, Sooil;Kim, Dongchoul
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.37 no.7
    • /
    • pp.665-667
    • /
    • 2013
  • Metal ions show various transitions in the cathode of a lithium-ion battery. The diffusion process of lithiumions and the phase transition in the cathode need to be thoroughly understood for the advanced design of an improved lithium-ion battery. Here, we employ a phase field model to simulate the diffusion of lithiumions and to study the phase transition in the cathode.

A viscoelastic-micropolar solid with voids and microtemperatures under the effect of the gravity field

  • Said, Samia M.
    • Geomechanics and Engineering
    • /
    • v.31 no.2
    • /
    • pp.159-166
    • /
    • 2022
  • The model of two-dimensional plane waves is analyzed in a micropolar-thermoelastic solid with microtemperatures in the context of the three-phase-lag model, dual-phase-lag model, and the Green-Naghdi theory of type III. Harmonic wave analysis is used to hold the solution to the problem. Numerical results of the physical fields are visualized to show the effects of the gravity field, magnetic field, and viscosity. The expression for the field variables is obtained generally and represented graphically for a particular medium.

Grain Growth and Texture Evolution of Mg: Phase Field Modeling (마그네슘의 결정립 성장과 집합조직: 상장모델 계산)

  • Kim, Dong-Uk;Cha, Pil-Ryung
    • Journal of Powder Materials
    • /
    • v.18 no.2
    • /
    • pp.168-171
    • /
    • 2011
  • We investigate grain growth behavior of poly-crystalline Mg sheet having strong basal fiber texture using phase field model for grain growth and micro-elasticity. Strong initial basal texture was maintained when external load was not imposed, but was weaken when external biaxial strain was imposed. Elastic interaction between elastic anisotropy of Mg grain and external load is the reason why texture evolution occurs.

Application of Phase-Field Theory to Model Uranium Oxide Reduction Behavior in Electrolytic Reduction Process (전해환원 공정의 우라늄 산화물 환원 거동 모사를 위한 Phase-Field 이론 적용)

  • Park, Byung Heung;Jeong, Sang Mun
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.16 no.3
    • /
    • pp.291-299
    • /
    • 2018
  • Under a pyro-processing concept, an electrolytic reduction process has been developed to reduce uranium oxide in molten salt by electrochemical means as a part of spent fuel treatment process development. Accordingly, a model based on electrochemical theory is required to design a reactor for the electrolytic reduction process. In this study, a 1D model based on the phase-field theory, which explains phase separation behaviors was developed to simulate electrolytic reduction of uranium oxide. By adopting parameters for diffusion of oxygen elements in a pellet and electrochemical reaction rate at the surface of the pellet, the model described the behavior of inward reduction well and revealed that the current depends on the internal diffusion of the oxygen element. The model for the electrolytic reduction is expected to be used to determine the optimum conditions for large scale reactor design. It is also expected that the model will be applied to simulate the integration of pyro-processing.