A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting.

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Solidification of dendritic alloys is modeled using stabilized finite element techniques to study convection and macrosegregation driven by buoyancy and shrinkage. The adopted governing macroscopic conservation equations of momentum, energy and species transport are derived from their microscopic counterparts using the volume-averaging method. A single domain model is considered with a fixed numerical grid and without boundary conditions applied explicitly on the freezing front. The mushy zone is modeled here as a porous medium with either an isotropic or an anisotropic permeability. The stabilized finite-element scheme, previously developed by authors for modeling flows with phase change, is extended here to ... continued below

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Dr. Zabaras, N. & Samanta, D. April 27, 2005.

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Solidification of dendritic alloys is modeled using stabilized finite element techniques to study convection and macrosegregation driven by buoyancy and shrinkage. The adopted governing macroscopic conservation equations of momentum, energy and species transport are derived from their microscopic counterparts using the volume-averaging method. A single domain model is considered with a fixed numerical grid and without boundary conditions applied explicitly on the freezing front. The mushy zone is modeled here as a porous medium with either an isotropic or an anisotropic permeability. The stabilized finite-element scheme, previously developed by authors for modeling flows with phase change, is extended here to include effects of shrinkage, density changes and anisotropic permeability during solidification. The fluid flow scheme developed includes streamline-upwind/Petrov-Galerkin (SUPG), pressure stabilizing/Petrov-Galerkin, Darcy stabilizing/Petrov-Galerkin and other stabilizing terms arising from changes in density in the mushy zone. For the energy and species equations a classical SUPG-based finite element method is employed with minor modifications. The developed algorithms are first tested for a reference problem involving solidification of lead-tin alloy where the mushy zone is characterized by an isotropic permeability. Convergence studies are performed to validate the simulation results. Solidification of the same alloy in the absence of shrinkage is studied to observe differences in macrosegregation. Vertical solidification of a lead-tin alloy, where the mushy zone is characterized by an anisotropic permeability, is then simulated. The main aim here is to study convection and demonstrate formation of freckles and channels due to macrosegregation. The ability of stabilized finite element methods to model a wide variety of solidification problems with varying underlying phenomena in two and three dimensions is demonstrated through these examples.

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  • Journal Name: International Journal for Numerical Methods in Engineering

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  • Report No.: DOE/ID/14396
  • Grant Number: FC36-02ID14396
  • DOI: 10.1002/nme.1423 | External Link
  • Office of Scientific & Technical Information Report Number: 850516
  • Archival Resource Key: ark:/67531/metadc783129

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  • April 27, 2005

Added to The UNT Digital Library

  • Dec. 3, 2015, 9:30 a.m.

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  • Jan. 9, 2017, 11:01 a.m.

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Dr. Zabaras, N. & Samanta, D. A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting., article, April 27, 2005; United States. (digital.library.unt.edu/ark:/67531/metadc783129/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.