multi-physics process simulation of static magnetic fields in … · 2012. 11. 9. · multi-physics...
TRANSCRIPT
Multi-Physics Process Simulation of StaticMagnetic Fields in High Power Laser Beam
Welding of Aluminum
Marcel Bachmann, Vjaceslav Avilov,
Andrey Gumenyuk, Michael Rethmeier
COMSOL Conference Milan 2012, October 10 – 12, 2012
Excerpt from the Proceedings of the 2012 COMSOL Conference in Milan
Overview
Introduction
Physical Principles
Numerical Modeling & Results
Experimental Observation
Conclusions
COMSOL Conference Milan 2012 Marcel Bachmann 1
Introduction
Applications deep-penetration laser beam welding
Ship-building industry
Reactor vessels & tanks
Power plant components
Aerospace industry
High-Speed Car FerriesAustan Ships
Aluminum Reactor VesselsMaulifab Engineers
NASA tank dome
COMSOL Conference Milan 2012 Marcel Bachmann 2
Introduction
Characteristics of the laser beam welding of thick metal parts
Related issues:
Intensive Marangoni convection
Buoyancy forces
Recoil pressure
Surface stability
Melt ejections
Non-uniform solidification
laser beam
COMSOL Conference Milan 2012 Marcel Bachmann 3
Introduction
Possibility to decelerate the melt? apply volumetric forces contact-less
all welding positions
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Physical Principles
Hartmann Effect – Flow Deceleration
u
j
B
FL
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Norm alized Velocity u/ umean
0.0
0.2
0.4
0.6
0.8
1.0
No
rma
lize
d c
ha
nn
el
wid
th
Ha2 = 0 analyt ic
Ha2 = 1 analyt ic
Ha2 = 25 analyt ic
Ha2 = 100 analyt ic
Ha2 = 0 sim ulat ion
Ha2 = 1 sim ulat ion
Ha2 = 25 sim ulat ion
Ha2 = 100 sim ulat ion
1.6
Liquid metal flow induces electric currents
Ratio of magnetic induced to viscous drag Ha2 = (BL)2σ/η
Resulting Lorentz force directed against melt movement
COMSOL Conference Milan 2012 Marcel Bachmann 5
Physical Principles
Permanent magnets applied to partial penetration welding
Mitigation of weld pool dynamics
Avoid turbulent flow pattern
Achieve parallel side walls
COMSOL Conference Milan 2012 Marcel Bachmann 6
Numerical Modelling
air
magnet
workpiece
50 mm
20 mm
50 mm
~21 mm
keyhole
Workpiece width: 40 mm
Magnet cross section:
50 mm × 50 mm
Vertical shift of the
magnet: 20 mm
Thermal
Simulation
Computational
Fluid Dynamics
Simulation
Electro-
magnetic
Simulation
Material
Properties
900,000 tetrahedral finite elements ⇒ 8,100,000 DoF
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Numerical Modelling
symmetry
WORKPIECE
inflowoutflow
adiabatic
free slip
Marangoni
adiabatic
free slip
Marangoni
adiabatic
free slip
free slip
adiabatic
Marangoni
adiabatic
free slip
Navier Stokes equations volume source term
F = −ρg − c1(1−fL)
2
f3L+ε
(u− uweld) + j×B
Buoyancy Solidification modelling Lorentz force
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Velocity distribution
B = 0 B = 0.5 T
B = 1.0 T B = 2.0 T
0.1
0
0.02
0.04
0.06
0.08
velo
city
, m
/s
Welding speed 0.5 m/min
3D flow ⇒ 2D flow
Buoyancy suppression
Marangoni flow suppression
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Velocity distribution
0.2 m/s
�5 0 5 10 15 20x, mm
40
42
44
46
48
50
z, m
m
0.2 m/s
�5 0 5 10 15 20x, mm
40
42
44
46
48
50
z, m
m
0.2 m/s
�5 0 5 10 15 20x, mm
40
42
44
46
48
50
z, m
m
0.2 m/s
�5 0 5 10 15 20x, mm
40
42
44
46
48
50
z, m
m
B=0 B=0.5 T
B=1 T B=2 T
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Temperature distribution
500
750
1000
1250
1500
1750
2000
2250
2500
Te m pe ra ture T, K
B = 0 B = 0.5 T B = 1 T B = 2 T
Marangoni convection suppressed at free surface
Weld bead shortening
Curvature in solidification line eliminated
COMSOL Conference Milan 2012 Marcel Bachmann 11
Macro Section Solidification line
0 2 4 6 8 10 12 14y, mm
25
30
35
40
45
50z
- pos
ition
, mm
B = 0B = 0.5 TB = 1.0 TB = 2.0 Ttheoretical case
Marangoni convection suppressed
Weld bead width decrease
Curvature in solidification line eliminated
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Local Hartmann Number
0.0 0.2 0.4 0.6 0.8 1.0magnetic flux density B, T
102
103
104
105
106
Har
tman
n n
um
ber
Ha2
laminar Hartmann number
turbulent Hartmann number
η = ηlam + ηturb
Jump in Ha2 = (BL)2σ/η
Once turbulence is damped
Ha2lam ≈ Ha2turb
Critical Ha2 for effective flow
control around B=0.4 TPosition: 5 mm behind keyhole and 5 mm below surface
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Experimental Observation
AlMg3 Welding Experiments with 16 kW disc laser system andpermanent magnets
magnet pole
magnet pole
Bmax around 0.5 T
Weld narrowing
Less surface waviness
Wine-glass shape ⇒ V shapeLaser power: 16 kWWelding velocity: 0.5 m/minFocus position: -4 mmShielding gas: 30 l Ar
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Experimental Observation
Reference B = 500 mT
⇒ Same tendency in experiments and simulations!COMSOL Conference Milan 2012 Marcel Bachmann 15
Experimental Observation
B = 500 mT
Same results with changed
orientation of the magnet field
Evidence for the occurance of
Hartmann effect
Laser power: 16 kWWelding velocity: 0.5 m/minFocus position: -4 mmShielding gas: 20 l Ar
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Conclusions
Influence of steady magnetic fields in partial penetration laser beamwelding of aluminium is shown
Significant changes in the velocity distributions
Maximal turbulence damping beginning with Ha2 ≈ 104
Weld pool geometry changes due to Hartmann effect with increasingmagnetic field from wine-glass shape to V shape
Changes in solidification line can influence mechanical andmetallurgical properties
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Thank you for your attention.
Grant No. GU 1211/2-1 Grant No. 17.625 N
COMSOL Conference Milan 2012, October 10 – 12, 2012