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ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
User-friendly FEA for Electromagnetic Forming
Dr. Charlotte Beerwald, Moritz Beerwald, Dr. Uwe Dirksen, Artur Henselek
Poynting GmbH, Dortmund, Germany
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Simulation of Electromagnetic Formingwith SMU-SimTool
User-friendly FEA of EMF with SMU-SimToolElectromagneticformingprocess EMF
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Company Profile
POYNTING company performs contract research, development and equipment manufacturing in the field of
Pulsed Power Technologies
Our intention is to bring new research-based technologies into application and make them available for diverse industrial branches.
Fields of activity comprise
• components and assemblies for pulsed power systems (high current, high voltage supplies) as well as complete turn-key systems,
• to design and build unique instrumentation for research and scientific use, and
• customer-specific equipment for industrial series production when processes are based on high-level electrical or electromagnetic field impulses
Pulse Modulator for ESS, Lundwith integratedHigh Voltage Power Supply225 kW, 6 kV
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Characteristic for this technology is that a large amount of energy [up to Megajoule range] will be charged and stored in a capacitance or in an inductance or in an accelerated mass to be suddenly discharged within a very short impulse of a few micro- or milliseconds.
As a result of this it is possible to generate temporarily extremely high power levels [in a Gigawatt range], which demands high electrical, but most of all mechanical requirements to the used components and structures.
Typically the peak values are much higher than the mean values. This can be used to initiate threshold reactions or to benefit from special non-linear effects.
Pulsed power technologies can be used advantageously if it is possible to achieve a better result compared to conventional methods, or if the pulsed power principle even enables a desired application for the first time.
Pulsed Power Technologies
What does ‘Pulsed Power‘ mean?
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
HV Power Suppliespower categoriesup to several hundred kW
Pulse Generatorse.g. SMU machinescompact or modular design
Components, Individual Parts, AssembliesTool Coil Design
Feasibility Studies
Product Range - Hardware
Pulsed Power Equipment
• The hardware product range of Poynting mainly consist of high-voltage power supplies, pulse generators, and accessory equipment
• Normally, in our high-current and high-voltage applications the high forces induced by the magnetic fields are undesired
• Nevertheless, applications exists where these high forces are welcome.
• In the Electromagnetic Forming EMF process the magnetic pressure impulse is used to form and join metallic workpieces
• SMU machines are special pulse generators usedfor the EMF process
• On the left side two coils for the EMF process areshown
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
High Current Switch
Workpiece(tubular)
C
Li
Ri
EMF – Process Principle
p = 1/2 µ0 H 2
µ0: permeability of vacuum
Magn. Pressure
Process Time
H: magn. field strength
• On the left side you can see a simplified process setup for Electromagnetic Forming
• The pulse generator is represented by its equivalent electrical circuit with resistance Ri, inductance Li, and capacitor bank C
• The Electromagnetic Forming process starts with charging the capacitor bank
• The energy in the capacitor bank is discharged if the high current switch is closed
• The high current switch must switch very fast and the power loss must be low (max. current can be up to 1000 kA)
• If the high current switch is closed a current starts to flow through thecoil
Electromagnetic Forming is a High Velocity Forming Process using the energy densityof a pulsed magnetic field to form or accelerateworkpieces of good electrical conductivity.
Pulse generator
Coil Current
Process Time
Compression Coil
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Magnetic Field Strength H(pressure zone)
EMF – Process Principle
p = 1/2 µ0 H 2
µ0: permeability of vacuum
Magn. Pressure
Process Time
H: magn. field strength
Coil Current
Process Time
• As the current flows through the coil a magnetic field develops around the coil
• The magnetic field induces eddy currents in the metallic workpiece which also develop a magnetic field
• The higher the electrical conductivity of the workpiece thehigher the eddy currents and the developed magnetic field
High Current Switch
Workpiece(tubular)
C
Li
Ri
Compression Coil
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Coil Current
Process Time
High Current Switch
Workpiece(tubular)
C
Li
Ri
Magnetic Field Strength H(pressure zone)
I (t) H (t) p (t)
SMU – Process Principle
p = 1/2 µ0 H 2
µ0: permeability of vacuum
Magn. Pressure
Process Time
H: magn. field strength
• If the magnetic field strength H is known the magneticpressure p can be determined
• If the pressure p is high enough the workpiece is plasticlyformed
• The current I directly influences the pressure and accordinglythe forming of the workpiece
• Electromagnetic Forming is a high velocity process and theprocess duration of workpiece forming is in the range of 10 µs to 1 ms
Compression Coil
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Compression
Expansion
Flat Forming
Electromagnetic Forming is a High Velocity Forming Process using the energy density of a pulsed magnetic field to form or accelerate workpieces of good electrical conductivity.
Process Typesresulting of the coil-workpiece arrangement
Capacitor Bank
High Current Switch
Workpiece(tubular)
Compression Coil
C
Li
Ri
SMU – Process Principle
• Electromagnetic Forming can be used to form tubes andsheets
• The used process type depends on the coil shape andthe coil-workpiece arrangement
1. Flat forming:A flat spiral coil can be used to form sheet metals
2. Compression:A metallic tube inside of a spiral coil can reducethe radius of the tube
3. Expansion:A metallic tube outside of a spiral coil can expandthe radius of the tube
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Fluid Pipes for Automotive Applications
(coated aluminium tube and steel fitting)
Assembling and Oil Tight Sealing of
Hydraulic Compen-
sating Bellows
Joining of Multi-Material Components
(high strength FRP – aluminium parts)Chassis
Components
(Cross-Steering
BMW M3 CSL)
Joining by EMF – Tubes + Profiles
Joining of Car Body Components
(aluminium spaceframe components)
• Electromagnetic Forming can be used for joining, cutting, and forming of tubes and sheet metals
• Joining of tube-shape workpieces is the most important process type at the moment. It is a mechanical joining where at least one joining partner is formed. The join can be realized as force-fit and form fit. At high impact velocities a firmly bonded join is also possible
• Due to the contact-less forming process no tool marks on the workpiece coated workpieces can be used
• Only the formed workpiece must have a good electrical conductivity
Joins with material combinations of different metals and metal / non-metal can be manufactured
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Fluid Pipes for Automotive Applications
(coated aluminium tube and steel fitting)
Assembling and Oil Tight Sealing of
Hydraulic Compen-
sating Bellows
Joining of Multi-Material Components
(high strength FRP – aluminium parts)Chassis
Components
(Cross-Steering
BMW M3 CSL)
Joining by EMF – Tubes + Profiles
Joining of Car Body Components
(aluminium spaceframe components)
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Research Project
Grant Agreement Nr: 609039Collaborative Project - FP7-2013-NMP-ICT-FOF(RTD)
Optimization of joining processes for new automotive metal-composite hybrid parts
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Relevant Propertiesfor Simulation of EMF Process
SMU-COMPACT 3020-FS (max. 30 kJ, max. 20 kV)
• Simulation of a manufacturing process requiresan understanding of the relevant processcomponents and properties
• For the EMF process an important processparameter is the current. It mainly depends on the SMU machine, the energy conduction systemand the consumer load which consist of the toolcoil and the workpiece
• These components build the discharge circuitwhich can be simplified to the equivalentelectrical circuit below. The consumer load isdescribed with Ra and La separatly becausethese values changes during the process
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Relevant Propertiesfor Simulation of EMF Process
SMU-COMPACT 3020-FS (max. 30 kJ, max. 20 kV)
• The current is responsible for creation of the magnetic fields• The magnetic fields creates the magnetic pressure which deforms the
workpiece• Deformation of the workpiece changes the inductance of the
consumer load• Joule heating in the conductors increase the temperature in the
conductors• Changes in the temperature also changes electrical and mechanical
properties of the components (workpiece, coil, etc.)
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Physical Domains and their Dependencies
Electrica loscilla ting
circu it
E lectro-m agnetic
fie ld
Tem peratureS tructura l
m echanics
• Modeling of the Electromagnetic Forming requires considering the “physical domains”:
• Electrical circuit• Electromagnetic field• Structural mechanics• Temperature
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Physical Domains and their Dependencies
Electrica loscilla ting
circu it
E lectro-m agnetic
fie ld
Tem peratureS tructura l
m echanics
• The “physical domains“ depend from each other and their values
change over process time• Simulation of the EMF process requires one simulation which can
solve all „physical domains“ or coupling of different simulations whichindividually solve the „physical domains“
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Element Selection
Electrica loscilla ting
circu it
E lectro-m agnetic
fie ld
Tem peratureS tructura l
m echanics
Phys. Domain
Circu124 / Circu125
2D 3D
Circu124 / Circu125
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
• Required components of the electrical circuit can bedescribed using the elements Circu124 and Circu125
• The electromagnetic fields can be presented using theelement Plane223 for 2D and Solid236 for 3D
• The structural mechanics and the changes in temperature can be described using the coupled-fieldelements Plane223 for 2D and Solid226 for 3D
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Simulation System Model
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Simulation System Model
The simulation model:
• Implementation starts with ANSYS v13 using ANSYS classic
• Fully automized using APDL scripts
• Two main sub-simulations (sparse solver)
• El-Mag-Simulation solves electrical circuit and electromagnetic fields
• Mech-Ther-Simulation solves structural mechanics and changes in temperature
• Both sub-simulations uses the same mesh. Mesh is automatically generated using a feature-
based description of the process components
• The types of the elements are updated between the sub-simulation and results are transfered
using the LDREAD APDL-command
• After each sub-simulation results are post-processed and can be evaluated by the user
• Number of sub-steps in the Mech-Ther sub-simulation are adjusted according to the maximum
velocity of elements
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Meshing
r
z
Compression Coil Field shaper
Tube
Mandrel
Symmetry axisat r = 0
Skin depth s in conductors(coil, field shaper, workpiece) must be considered
Air must be meshed
𝛿𝑠 =1
𝜋 𝑓 𝜇 𝜅
: Frequency of current
: Magnetic permeability: Electrical conductivity
𝑓𝜇𝜅
Skin depth
Skin depth s in copperat = 10 kHz: s = 660 µm𝑓
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Meshing
r
z
Compression Coil Field shaper
Tube
Mandrel
Symmetry axisat r = 0
Skin depth s in conductors(coil, field shaper, workpiece) must be considered
Air must be meshed
𝛿𝑠 =1
𝜋 𝑓 𝜇 𝜅
: Frequency of current
: Magnetic permeability: Electrical conductivity
𝑓𝜇𝜅
Skin depth
Skin depth s in copperat = 10 kHz: s = 660 µm𝑓
• Determination of the electromagnetic fields requires meshing the air between
the workpiece, joining partner, coil, and field shaper1
• The EMF process uses AC currents which requires considering the skin effect
in meshing the components. The skin effect describes the effect that the
current density is not equal across the cross section at AC currents. Instead of
it decreases from the surface to the inner parts. At the skin depth the current
is decreased to 1/e of the current on the surface.
Describing the skin effect accurately requires suitable number of elements
and elements sizes in the coil, field shaper, and workpiece
1Field shaper is used to concentrate the magnetic field generated by the coil
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Coupling of Electrical Circuit and Coil
r
z
Symmetry axisat r = 0
Compression Coil
Field shaper
Tube
Mandrel
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Coupling of Electrical Circuit and Coil
r
z
Symmetry axisat r = 0
Compression Coil
Field shaper
Tube
Mandrel
• The pulse generator and the energy conduction system are summarized in theequivalent electrical circuit using the resistor R, the inductor L and thecapacitor C
• The electrical circuit is coupled to the coil elements using a constraintequation
• At the beginning of the simulation the capacitor is initialized with the loadvoltage Ucircuit
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Contact Definition
• Using one mesh for El-Mag sub-simulation and Mech-Ther sub-simulations means that between the contact partners alwaysexist elements representing the air. These elements are requiredfor computation of the magnetic field
• A contact gap of at least 50 µm must be defined to avoidcollapsing of the air elements
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
System Model of SMU-SimTool
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
System Model of SMU-SimTool
• The simulation model for the EMF process is rather complicated• The product and process designer do not want to take care on these aspects!• Poynting has developed the simulation tool SMU-SimTool which hides the setup of a 2D
process simulation and the required pre- and post-processing for the EMF process• SMU-SimTool is implemented for operating systems Windows and Linux• SMU-SimTool is separated in two components: frontend and backend• SMU-SimTool frontend
• Installed on user side• Feature-based modelling of the product and process components. Process
components can be selected from libraries.• Configuration of main parameters of simulation process such as final process
time, contact gap and so on• Controlling of simulation (start, stop, restart)• Visualization of already post-processed relevant simulation results
• SMU-SimTool backend• Running at Poynting• SMU-SimTool frontend transfers product and process data to the backend if the
users starts or restarts the simulation• The backend automatically starts the simulation model on ANSYS• After each simulation step relevant results are post-processed and transferred to
the users SMU-SimTool frontend for evaluation
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
SMU-SimTool: Modelling in 5 Steps
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
SMU-SimTool: Modelling in 5 Steps
• Modelling of the product and process components is feature-based
• For each component a base type is selected and further detailed using a small
number of parameters
• Material, coil, and pulse generators can be easily selected from libraries
• The selected SMU machine is configured by switching on the requested
capacitor banks and defining the requested load energy or load voltage
• Only five steps are required for defining the model!
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
SMU-SimTool: Application Example
r
z
Compression Coil Field shaper
TubeØ75mm x 2.5mm
Mandrel withconical groove
Symmetry axisat r = 0
Desired time curvesat certain position z = 0
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
SMU-SimTool: Application Example
r
z
Compression Coil Field shaperFF75l15
Tube, AW6060 T6Ø75mm x 2.5mm
Mandrel, S235conical groove
Symmetry axisat r = 0
Desired time curvesat certain position z = 0
• The application examples shows the simulation of the EMF process type
compression. A tube is formed on an inner joining partner. Therefore a coil with
four turns and a field shaper are used.
• After each load step the following data is sent to the SMU-SimTool frontend
and displayed as curve
• Current
• At one specified location on the outer side of the tube
• Displacement in x-direction
• Velocity in x-direction
• Magnetic pressure
On next page:
• Beside time data also contour plots are created and transferred to the SMU-
SimTool frontend
All data transferred to the SMU-SimTool frontend is stored locally and can offline
be further evaluated
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
SMU-SimTool: Application Example
ANSYS Conference & 32nd CADFEM Users' Meeting 2014June 4 – 6, 2014, NCC Ost, Messe Nürnberg
Summary and Outlook
Fully-coupled simulation for EMF process• APDL scripts with two main simulations using 1 mesh
User-friendly FEA of EMF process with SMU-SimTool• No FEA simulation knowledge required• Fast modelling due to feature-based modelling• Define process time and press START button• Relevant simulation results are already post-processed
• Time data• Contour plots
Future work• Multi-frame restart• Automatic air-remeshing in 3D• …