Fully coupled multiphysics finite element simulation of
magnetic pulse welding of flat parts
Uwe Dirksen
Poynting GmbH, Dortmund, Germany
Final Seminar, 24th February 2016, BWI, Ghent, Belgium
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
1) Application of Electromagnetic pulse welding MPW
2) Fully coupled multiphysics finite element simulation
3) Finite element analysis in product and process design for MPW
Overview
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Magnet Pulse Welding MPW of sheet metal with inserted composite
Magnet Pulse Welding MPW of composite sheets with metal inserts(assembling of hybrid parts)
Flange plate (aluminium or sandwich)
Clamping sheet (aluminium flyer)
Composite part,cone with flanged end
polymer/composite
embeddedaluminium
metallic joining partner
composite sheetor prepreg
aluminium sheet
metal base plate / sheet
welded sandwich sheet
Welding of flat
Metal-Composite hybrid Parts
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Electromagnetic Forming (EM)
of Sheet Metal – Principle
Flat forming setup and process principle
flat coil (multi-turn)die / drawing
ring
workpiece (forming states)
coil current I magnetic field B~H
Zoom direction induced current
direction coil current
resulting pressure direction
Magne
tic P
ressure
(i
n M
Pa
)
Time (in µs)
Magnetic Pressure Impulse
acting between tool coil and workpiece at a certain radial position,
but at r = 0 always p(t) = 0
)()(2
1)( 2
diff
2
gap0 tHtHtp
I (t) H (t) p (t)
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Electricaloscillating
circuit
Electro-magnetic
field
TemperatureStructuralmechanics
Numerical Modelling of Process
Flat forming setup and process principle
flat coil (multi-turn)die / drawing
ring
workpiece (forming states)
coil current I magnetic field B~H
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Electricaloscillating
circuit
Electro-magnetic
field
TemperatureStructuralmechanics
Physical Domain
Circu124 / Circu125
ANSYS 2D Element Types
Plane233: 2D 8 node electromagnetic solid
Plane223: 2D 8 node coupled-field solid
Plane223: 2D 8 node coupled-field solid
Solid226: 3D 20 node coupled-field solid
Solid226: 3D 20 node coupled-field solid
Solid236: 3D 20 node electromagnetic solid
Electrical circuit
Electromagn. field
Structural mech.
Temperature
Physical Domain
Circu124 / Circu125
ANSYS 3D Element Types
Electrical circuit
Electromagn. field
Structural mech.
Temperature
Physical Domains and Coupling within ANSYS
Selected Finite Element Types
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
• 1 mesh for allphysical domains
• Fully automized simulationusing ANSYS APDL script
• Solver: Sparse
System Model
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Example of Finite Element Analysis
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Skin depth s in conductors (coil, workpiece) must be considered
Air must be meshed
: Frequency of current
: Magnetic permeability
: Electrical conductivity
Skin depth
Skin depth s in copper at = 10 kHz: s = 660 µm
Target sheet Flyer sheet
Composite
Coil
Meshing and Air-Remeshing
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Nodes:
Elements:
1 Time-step:
638910
422731
30 - 45 min
Nodes:
Elements:
1 Time-step:
66584
44032
1- 1.5 min
3D Finite Element Simulation
Meshing and Performance
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
2D planar simulation model for sheet partsNo symmetry axis exist!
Constraint Equation for
Coupling of electrical RLC Circuit
Constraint equation:
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Contact Offset
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Process time t= 3.0 µs
Coil + flyer Coil Flyer
Evaluation of Product and Process Design
Current DensityProcess time t= 3.0 µs
Top view
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Rectangular single-turn test coilFrec140x130-1/10
Plastic deformation of copper conductor, caused by local pressure overload along all edges (clearest in the corners)
Deformation indicates the current distribution facing the flyer sheet
Current 400 kA10 discharges
Evaluation of Product and Process Design
Test Coil Wearing
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
Evaluation of Product and Process Design
Flyer Sheet Displacement
Process timet= 12.5 µs
View direction
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
lower limit curve is a function of strength / hardness of materials
upper limit curve is a limit of kinetic energy resulting in undesired melted layer
explosive cladding allows to assume stationary conditions,while MPW is used for small workpiece areas resulting in transient geometrical conditions
FE Process Simulation needed to determine, analyse and predict weldability
nevertheless, dependencies of collision point velocity and collision angle seem to be relevant for process design
"weldability window"
vc,crit vc,max = f(cb,)
lower limit
curve
upper limit curve
vp = 2 vd sin( / 2)geometrical relation
between vc, vp and :
state of the art is determined by basic knowledge of explosive welding (cladding)
Fundamental Investigations of MPW
Weldability Window
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
d
α
Determination of Collision Angle:
Determination of Collision Point Velocity:
1.Determination of collision points at each load step2.Computation of velocity of collision point between load steps
Collision Angle and
Velocity of Collision Point
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
vy
N(x,y)
Welding Parameter Impact Velocity
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
An
gle
at c
olli
sio
n p
oin
t
in d
eg
lower limit curve (Wittman):
= k1 /vp HV/
HV: Vickers Hardness in N/m2
: material density
surface descriptionk1: 0,6 high quality cleaned
1,2 imperfectly cleaned
Weldability Window -
Collision Point Velocity and AngleAS23 (peel test, dye penetrant test)
Flyer sheet
Target
sheet
1,0 mm
two welded areas
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
0 0.34 0.57 0.80
Total mechanical strain v. Mises
0.12 >1.05
Axisymmetric FEALoad energy 18 kJOverlap o= 0 mm -60 140 273 406
Velocity dy/dt in m/s
7 >540
t= 18.4 µs
One potential welding zone
Axisymmetric FEALoad energy 18 kJOverlap o= 3 mmChamfer 45°, 1 mm 0 0.23 0.38 0.53
Total mechanical strain v. Mises
0.08 >0.69 0 180 300 420
Velocity dy/dt in m/s
60 >540
t= 21.5 µs
Two potential welding zones
High strains
Low contact angle
Optimization of Product Design
and Process Parameters
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
90mm in
FEA
Virtual Welding
Welding / bonding of joined materials is notsimulated in the structural mechanics sub-simulation!
No final bonding of components in welded zone
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
90mm in
FEA
Virtual Welding
Feature „Critical bonding temperature“ ofcontact element Contact172/Contact174 (ANSYS)is used to implement „Virtual Welding“
Load curve is used to specifythe bonded contact elements
Final Seminar, 24th February 2016
Belgium Welding Institute, Ghent
90mm in
FEA
Virtual Welding
Feature „Critical bonding temperature“ ofcontact element Contact172/Contact174 (ANSYS)is used to implement „Virtual Welding“
Load curve is used to specifythe bonded contact elements