Metallurgical and Materials Transactions B

, Volume 31, Issue 3, pp 515–527 | Cite as

A computational model for defect prediction in shape castings based on the interaction of free surface flow, heat transfer, and solidification phenomena

  • S. Bounds
  • G. Moran
  • K. Pericleous
  • M. Cross
  • T. N. Croft
Article

Abstract

High-integrity castings require sophisticated design and manufacturing procedures to ensure they are essentially macrodefect free. Unfortunately, an important class of such defects—macroporosity, misruns, and pipe shrinkage—are all functions of the interactions of free surface flow, heat transfer, and solidication in complex geometries. Because these defects arise as an interaction of the preceding continuum phenomena, genuinely predictive models of these defects must represent these interactions explicitly. This work describes an attempt to model the formation of macrodefects explicitly as a function of the interacting continuum phenomena in arbitrarily complex three-dimensional geometries. The computational approach exploits a compatible set of finite volume procedures extended to unstructured meshes. The implementation of the model is described together with its testing and a measure of validation. The model demonstrates the potential to predict reliably shrinkage macroporosity, misruns, and pipe shrinkage directly as a result of interactions among free-surface fluid flow, heat transfer, and solidification.

List of Nomenclature

A

1 or ∂/∂t in Table I

C

Carmen-Kozeny constant

Cp

specific heat

D

mold thickness

d

characteristic “structure” or grain size dimension

f

solid fraction

fc

coherency point

fe

eutectic point

Fμ

smooth switching function

g

acceleration due to gravity

g

gas

h

enthalpy

K

permeability

L

latent heat

m

metal

n

normal vector

P

pressure

Pames

ambient pressure

PI

initiation pressure

Qair

air flow rate through the mold

Qv

volume source

Qs

surface flux source

R

flow resistance in the mold

r

pore radius

S

mass sources

Sv

specific surface area

SD

Darcy source term

T

temperature

u

liquid velocity

vslip

slip velocity

ε

mold porosity

μ

viscosity

ρ

density

φ

transported variable

σ

surface tension

φm

metal fraction

Γ

diffusion coefficient

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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2000

Authors and Affiliations

  • S. Bounds
    • 1
  • G. Moran
    • 1
  • K. Pericleous
    • 1
  • M. Cross
    • 1
  • T. N. Croft
    • 1
  1. 1.the Centre for Numerical Modelling and Process AnalysisUniversity of GreenwichLondonUnited Kingdom

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