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Search Publications by: James A. Warren (Fed)

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Displaying 51 - 75 of 90

Modeling the Formation and Dynamics of Polycrystals in 3D

October 1, 2005
Author(s)
R Kobayashi, James A. Warren
Phase field models of solidification have been extended to include grain boundaries, using a variety of techniques. A model developed by Kobayashi et. al cite} has been used to model a host of physical phenomena, but has so far been confined to two

FiPy: A Finite Volume PDE Solver Using Python

September 1, 2005
Author(s)
Daniel Wheeler, Jonathan E. Guyer, James A. Warren
The solution of coupled sets of partial differential equations (PDEs) is ubiquitous in continuum models for phase transformations, such as in phase field or level et simulations. We are developing an object-oriented PDE solver, written in the Python

Exact Solution of a Field Theory Model of Frontal Photopolymerization

August 11, 2005
Author(s)
James A. Warren, J Cabral, Jack F. Douglas
Frontal photopolymerization (FPP) provides a versatile method for the rapid fabrication of solid polymer network materials by exposing photosensitive molecules to light. Dimensional control of structures created by this process is crucial in applications

On the Growth and Form of Spherulites

July 1, 2005
Author(s)
L Granasy, T Pusztai, G -. Tegze, James A. Warren, Jack F. Douglas
Many structural materials (metal alloys, polymers, minerals, etc.) are formed by quenching liquids to form crystalline solids. This highly non-equilibrium process leads to an extraordinary variety of polycrystalline growth patterns that are broadly termed

Lateral Deformation of Diffusion Couples

April 1, 2005
Author(s)
William J. Boettinger, Geoffrey B. McFadden, Sam R. Coriell, R F. Sekerka, James A. Warren
A model is proposed to describe the shape change (displacement field) of a binary diffusion couple when the intrinsic (lattice) diffusivities of the two substitutional atomic species differ. As for the Kirkendall effect, the displacement is due the

Modelling Polycrystalline Solidification Using Phase Field Theory

October 1, 2004
Author(s)
L Granasy, T Pusztai, James A. Warren
We review recent advances made in phase field modelling of polycrystalline solidification. Areas covered include the development of theory from early approaches that allow for only a few crystal orientations, to the latest models relying on a continuous

Phase Field Modeling of Solidification Under Stress

July 1, 2004
Author(s)
Julia Slutsker, Alexander L. Roytburd, James A. Warren, Geoffrey B. McFadden, William J. Boettinger
A phase-field model that includes stress field during non-isothermal solidification of a one-component system has been developed. The model has been applied to solidification and melting of confined spherical volumes. It has been shown that at some

Nucleation and Polycrystalline Solidification in Binary Phase Field Theory

April 1, 2004
Author(s)
L Granasy, T Pusztai, T Borzsonyi, James A. Warren, B Kvamme, P F. James
We present a phase field theory for the nucleation and growth of one and two-phase crystals solidifying with different crystallographic orientations in binary alloys. The accuracy of the model is tested for crystal nucleation in single-component systems

Phase-Field Modeling for Eutectic Solidification

April 1, 2004
Author(s)
Jonathan E. Guyer, William J. Boettinger, James A. Warren, Geoffrey B. McFadden
A diffuse interface (phase field) model for a simple electrochemical system is developed. We describe the minimal set of components needed to model an electrochemical interface and present a Lagrangian derivation of te governing equations. With a simple

Phase-Field Models for Eutectic Solidification

April 1, 2004
Author(s)
D J. Lewis, T Pusztai, L Granasy, James A. Warren, William J. Boettinger
This article discusses two methods for modeling eutectic solidification using the phase-field approach. First, the multi-phase field model is used to study the three-dimensional morphological evolution of binary eutectics. Performing the calculations in

Phase Field Modeling of Electrochemistry. I. Equilibrium

February 1, 2004
Author(s)
Jonathan E. Guyer, William J. Boettinger, James A. Warren, Geoffrey B. McFadden
A diffuse interface (phase field) model for an electrochemical system is developed. We describe the minimal set of components needed to model an electrochemical interface and present a variational derivation of the governing equations. With a simple set of

Phase Field Modeling of Electrochemistry. II. Kinetics

February 1, 2004
Author(s)
Jonathan E. Guyer, William J. Boettinger, James A. Warren, Geoffrey B. McFadden
The kinetic behavior of the phase field model described in (J.E. Guyer, W.J. Boettinger, J.A. Warren and G. B. McFadden, Phase field modeling of electrochemistry: Equilibrium, unpublished) is explored for advancing (plating) and receding (corroding)

Extending Phase Field Models of Solidification to Polycrystalline Materials

December 1, 2003
Author(s)
James A. Warren, R Kobayashi, A E. Lobkovsky, W Carter
We present a new, two dimensional phase field model of grain boundary statics and dynamics. We begin with a brief description and physical motivation of the crystalline phase field model. The description if followed by characterization and analysis of some

Phase Field Modelling of Alloy Polycrystals

May 1, 2003
Author(s)
James A. Warren, I Loginova, L Granasy, T Borzsonyi, T Pusztai
Recent results using a phase field model of polycrystalline alloy dynamics are presented, using two numerical techiques: adaptive grids and parallel grids. The growth of alloy dendrites, and their subsequent impingement to form grain boundaries is

Three Dimensional Phase Field Modeling of Binary Eutectics

May 1, 2003
Author(s)
D J. Lewis, William J. Boettinger, James A. Warren
A multi-phase field model was used to study the three-dimensional dynamics of morphology evolution in binary eutectics. Performing the calculations in three dimensions enables the study of the transition from rod-like to lamellar morphology and the study

Growth Pulsations in Symmetric Dentritic Crystallization in Thin Polymer Blend Films

May 1, 2002
Author(s)
V Ferreiro, Jack F. Douglas, James A. Warren, Alamgir Karim
The crystallization of polymeric and metallic materials normally occurs under conditions far from equilibrium, leading to patterns that grow as propagating waves into the surrounding unstable fluid medium. The Mullins-Sekerka instability causes these wave

Phase Field Modeling Applied to the Double Layer

May 1, 2002
Author(s)
Jonathan E. Guyer, William J. Boettinger, James A. Warren, Geoffrey B. McFadden
We present the first application of phase field modeling to electrochemistry. A free energy functional that includes the electrostatic effect of charged particles leads to rich interactions between concentration, electrostatic potential, and phase

Non-Equilibrium Pattern Formation in the Crystallization of Polymer Blend Films

April 1, 2002
Author(s)
V Ferreiro, Jack F. Douglas, James A. Warren, Alamgir Karim
The crystallization of polymeric and metallic materials normally occurs under conditions far from equilibrium. The morphologies formed reflect a competition between order associated with the symmetries of the equilibrium crystal geometry and disorder

Model of Electrochemical Double Layer" Using the Phase Field Method

March 20, 2002
Author(s)
William J. Boettinger, Geoffrey B. McFadden, James A. Warren, Jonathan E. Guyer
We present the first application of phase field modeling to electrochemistry. A free energy functional that includes the electrostatic effect of charged particles leads to rich interactions between concentration, electrostatic potential, and phase