fully coupled multiphysics finite element simulation of magnetic

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



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



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)



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



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



• 1 mesh for allphysical domains

• Fully automized simulationusing ANSYS APDL script

• Solver: Sparse

System Model



Example of Finite Element Analysis



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



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



2D planar simulation model for sheet partsNo symmetry axis exist!

Constraint Equation for

Coupling of electrical RLC Circuit

Constraint equation:



Contact Offset



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



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


Test Coil Wearing




Flyer Sheet Displacement

Process timet= 12.5 µs

View direction



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



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



vy

N(x,y)

Welding Parameter Impact Velocity



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



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



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



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

fully coupled multiphysics finite element simulation of magnetic

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