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Numerical Heat Transfer, Part A: Applications
An International Journal of Computation and Methodology
Volume 71, 2017 - Issue 11
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Original Articles

Investigation on the effect of the thermal dynamic, evaporation, and alternative material properties in a laser melt pool with a developed 2D model based on the VOSET method

, , , , &
Pages 1104-1122 | Received 21 Jan 2017, Accepted 27 Apr 2017, Published online: 14 Jun 2017
 

ABSTRACT

The melt pool is the general process of the laser additive manufacturing process. An in-depth understanding of the evolution of the melt pool will facilitate obtaining an optimum mechanical performance. In this paper, a novel 2D transient model is presented, which considers most physical phenomena taking place in the laser melt process and incorporates a coupled multiphase capture method. This model is validated by comparing it to Han’s research. Then an investigation on the transient thermal dynamic in the melt pool including quenching time is carried out, and the effects of evaporation and alternative material properties on the evolution of the melt pool are discussed. The results show that the deformation of the free surface and the temperature in the workpiece both increase with energy input. After quenching, the temperature in the workpiece decreases sharply and the melt pool also shrinks. The evaporation effect is vigorous in the center of the melt pool and negligible in the periphery. The material properties have significant influence on the evolution process because the convection and diffusion in the melt pool are directly dominated by them.

Nomenclature

C=

volume fraction function

Cp=

specific heat, J/(kg · K)

d=

distance from the grid to the interface, m

g=

gravity, m/s2

gl=

liquid fraction in the melt pool

H=

enthalpy, J/kg

ΔH=

latent heat of melting, J/kg

κ0=

permeability coefficient

Lv=

latent heat of evaporation, J/kg

pr=

vapor recoil force, N

P=

pressure, Pa

Plaser=

laser power, W

ΔPe=

Peclet number

QA=

radiation energy of point A at 100 ms, W

Qct=

radiation energy at current time, W

t=

time, s

T=

temperature, K

Tm=

melting temperature, K

T0=

ambient temperature, K

Ts=

solidification temperature, K

Tsurf=

surface temperature of melt pool, K

U=

heat of evaporation per Avogadro’s number atoms

=

velocity, m/s

Vdv=

rate of the free surface deformation, m/s

V0=

sound velocity in the workpiece, m/s

x, y=

coordinate directions, m

δx=

distance between the adjacent grid points

Greek symbols=
β=

coefficient of volume expansion

γ=

surface tension coefficient, N/m

ε=

emissivity

ε0=

transition region thickness

ζ=

small number

η=

absorptivity coefficient

κ=

interface curvature

λ=

thermal conductivity, W/(m•K)

μ=

dynamic viscosity coefficient, Pa•s

ρ=

density, kg/m3

σ=

Stefan Boltzmann constant, 5.67 × 10−8 W/(m2 · K4)

τ=

radiation ratio

ϕ=

level set function

Subscripts=
1=

liquid phase

2=

gas phase

i, j=

index of point

surf=

surface

Abbreviations=
BFC=

body-fitted coordinates

CSF=

continuum surface force

LBAM=

laser-based additive manufacture

LS=

level set

SLM=

selective laser melting

VOF=

volume of fluid

Nomenclature

C=

volume fraction function

Cp=

specific heat, J/(kg · K)

d=

distance from the grid to the interface, m

g=

gravity, m/s2

gl=

liquid fraction in the melt pool

H=

enthalpy, J/kg

ΔH=

latent heat of melting, J/kg

κ0=

permeability coefficient

Lv=

latent heat of evaporation, J/kg

pr=

vapor recoil force, N

P=

pressure, Pa

Plaser=

laser power, W

ΔPe=

Peclet number

QA=

radiation energy of point A at 100 ms, W

Qct=

radiation energy at current time, W

t=

time, s

T=

temperature, K

Tm=

melting temperature, K

T0=

ambient temperature, K

Ts=

solidification temperature, K

Tsurf=

surface temperature of melt pool, K

U=

heat of evaporation per Avogadro’s number atoms

=

velocity, m/s

Vdv=

rate of the free surface deformation, m/s

V0=

sound velocity in the workpiece, m/s

x, y=

coordinate directions, m

δx=

distance between the adjacent grid points

Greek symbols=
β=

coefficient of volume expansion

γ=

surface tension coefficient, N/m

ε=

emissivity

ε0=

transition region thickness

ζ=

small number

η=

absorptivity coefficient

κ=

interface curvature

λ=

thermal conductivity, W/(m•K)

μ=

dynamic viscosity coefficient, Pa•s

ρ=

density, kg/m3

σ=

Stefan Boltzmann constant, 5.67 × 10−8 W/(m2 · K4)

τ=

radiation ratio

ϕ=

level set function

Subscripts=
1=

liquid phase

2=

gas phase

i, j=

index of point

surf=

surface

Abbreviations=
BFC=

body-fitted coordinates

CSF=

continuum surface force

LBAM=

laser-based additive manufacture

LS=

level set

SLM=

selective laser melting

VOF=

volume of fluid

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