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Katja Karola Holzer Impulse forming process

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The explosive forming method was investigated numerically for aluminium alloy sheet.
Numerical investigation of
explosive forming with the help
of QForm and Altair Radioss
Katja Holzer
12.10.2018
IAESTE Internship 03.09. – 12.10.2018
At Moscow Polytech
Department of Material Forming and Additive Technologies
Michael Petrov
Outline
1) About me
2) Explosive Forming
3) Simulation in QForm
4) Introduction to HyperWorks RADIOSS
5) Forming with RADIOSS
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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1) About me
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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2) Explosive Forming
• Explosive charge replaces punch used in conventional forming
• Hight Velocity Forming process (HVF), 20 – 300
1
s
• Explosives: TNT, Dynamite, gaseous mixtures, propellants etc.
 Empirical
+ Low cost tooling
 Not observable
+ No limitation in geometry
 High labour cost
+ Metals deform more readily under high
strain rates  Titanium, Tungsten alloys
 No mass production
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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2) Explosive Forming – Contact / Confined type
Carriage
Explosive
Enclosure
• Pressure/shock wave in direct contact with
workpiece
• Mostly tubular
• Workpiece collapses into die cavity
Workpiece
+ More efficient
 Geometric limitations
Die
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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2) Explosive Forming – Stand off / Unconfined type
Enclosure
Water
Explosive
• Explosive placed in medium (water)
• Defined stand off distance S
• Semi-empirical descriptions of pressure on
surface available
S
Role of water:
Workpiece
• Energy transfer medium
Vacuum
Die
Katja Holzer: Simulation of Explosive Forming
• Uniform transfer of energy
• “Smoothen” of shock wave
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2) Explosive Forming - Video
• https://www.youtube.com/watch?v=54FBjdcEbIg – 00:20
• https://www.youtube.com/watch?v=i5OgIcR0DXc – 02:00
Katja Holzer: Simulation of Explosive Forming
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3) Simulation in QForm - Setup
Geometry
Material
• Die
• Die: 5XNM, non deformable
250
200
• WP: C45, constant yield stress
• 20 °C, no lubrication
Mesh
• Die: free
250
300
20
• Max. element size 1,5mm
R5
• Workpiece 300x250x4
Katja Holzer: Simulation of Explosive Forming
Simulation parameters
• Setup 1: default time step
• Setup 2: max. time step 1 ms
Moscow, 12.10.2018
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3) Simulation in QForm - Setup
Load
• Decaying pressure
with Θ – decay time
and Pm – peak pressure
dependent of explosive, charge weight
and stand off distance
• Reduced speed of shock wave
• Used to simulate „plug cushion forming“
Aim
• Simulate short sequence of events
in eplosive forming  strain rates, time step
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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3) Simulation in QForm – Results Strain Rate
Setup 1
Katja Holzer: Simulation of Explosive Forming
1
s
Setup 2
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3) Simulation in QForm – Results Mean Stress [MPa]
Setup 1
Katja Holzer: Simulation of Explosive Forming
Setup 2
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3) Simulation in QForm – Conclusion
Time Scale
Automatic time step
sufficient when
deformed;
otherwise manually
adaption needed
Strain Rate
Mean Stress
Strain rates of
1
~106 very high;

experimentally for
1
Al alloy ~ 104
Pressure decay can
be indicated

• Vaildation with experimental data
• Is indication of acting pressure needed when no deformation appears?
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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4) Introduction to HyperWorks RADIOSS
• Explicit solver
• Mainly used for crash analysis
• No units
• No checks for reasonability
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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4) Introduction to HyperWorks RADIOSS – Crash Box
• Try 1
Katja Holzer: Simulation of Explosive Forming
• Try 2 - Displacement
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5) Forming with RADIOSS – Setup
• Pre-studies
• No multi-physics simulation
• Valid for all following Simulations
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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16
17
18
19
50
20
21
5) Forming with RADIOSS – Result
• Input and Output
files generated
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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4) Forming with RADIOSS – Plasticity
• Setup equal
• isotropic elasto-plastic material, (Mat2)
Johnson-Cook empirical material model
• material stress as a function of strain, strain rate
and temperature
 No failure criterion
+ Work hardening
 High increase in computational effort
+ Effect of plastic strain
+ Effect of strain rate
Katja Holzer: Simulation of Explosive Forming
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5) Forming with RADIOSS – Plasticity Setup
• Total time 5 (s)
• Load applied for 1 (s)
• 2 Materials
• Mat 1 – Ideal elastic
• Mat 2 – Isotropic elasto-plastic
Katja Holzer: Simulation of Explosive Forming
Moscow, 12.10.2018
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5) Forming with RADIOSS – Plasticity Result
Displacement
Displacement
Mat1 – Ideal elastic
Mat2 – Isotropic elasto-plastic
Katja Holzer: Simulation of Explosive Forming
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5) Forming with RADIOSS – further steps
• Implement plastic material model
• Check the interface defintion
• Validation with experiments/experimental data
• Multi-physics simulation
Katja Holzer: Simulation of Explosive Forming
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Теги
impulse forming, numerical simulation, explosive forming, QForm VX, Altair Radioss
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