Expansion Jianhui Shang, Steve Hatkevich, Larry Wilkerson American - - PowerPoint PPT Presentation

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Expansion Jianhui Shang, Steve Hatkevich, Larry Wilkerson American - - PowerPoint PPT Presentation

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Experimental Study and Numerical Simulation of Electromagnetic Tube Expansion Jianhui Shang, Steve Hatkevich, Larry Wilkerson American Trim LLC, Lima, Ohio USA *Thank Professor Glenn Daehn and Mr. Geoffrey Taber of the Ohio State University for

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April 24-26, 2012 – Dortmund, Germany

Experimental Study and Numerical Simulation of Electromagnetic Tube Expansion

Jianhui Shang, Steve Hatkevich, Larry Wilkerson

American Trim LLC, Lima, Ohio USA

ICHSF 2012

*Thank Professor Glenn Daehn and Mr. Geoffrey Taber of the Ohio State University for the velocity measurement using PDV, and Pierre L'eplattenier of Livermore Software Technology Corporation for LS-DYNA software support

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ICHSF 2012 Motivation

1. Electromagnetic forming involves large deformation, high velocity and high strain rate. 2. Tube expansion is a simple 2D axisymmetric forming process. 3. Photon Doppler Velocimeter (PDV) enables the reliable measurement of high velocity. 4. Electromagnetism module of LS-DYNA allows the simulation of electromagnetic forming. 5. Combination of PDV and LS-DYNA can help the study of the dynamic behavior of aluminum alloys at high strain rate and high velocity.

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ICHSF 2012 Procedure

Electromagnetic Tube Expansion Experiment

Tube Expansion Velocity PDV Current through Coil Rogowski coil

LS-DYNA Electromagnetism Simulation

Input Material Properties including Dynamic Behavior Input Tube Expansion Velocity Output Comparison Determine if material properties are suitable

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ICHSF 2012 Basic Layout of Electromagnetic Forming

Charging System Capacitor bank High current switch Coil Tube

+ + + + + +

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ICHSF 2012

Charging System Capacitor bank High current switch Coil Tube Rogowski Coil PDV Probe B PDV Probe A

+ + + + + +

Experimental Set-up

Rogowski coil measures current; PDV measures expansion velocity.

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ICHSF 2012 Capacitor Bank Used

A 16kJ Magneform machine in OSU (1) Maximum charging voltage is 8.66kV; (2) Total capacitance is 426µF; (3) Internal inductance is around 100nH;

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ICHSF 2012 Three-turn Coil

OD: 61mm; Gap between turns: 1.8mm; 6.3mm x 6.3mm cross section

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ICHSF 2012 Al6061-T6 Tube

PDV probe A (Middle of 3-turn coil) PDV probe B (10mm away from Probe A) OD of Al tube: 63.5 mm; Wall thickness: 0.89mm; Length: 45mm

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ICHSF 2012 Velocity and Current Measurements (0.8 kJ)

  • 40
  • 20

20 40 60 80

  • 50

50 150 250 350 450

Time (micro-second) Velocity (m/s)

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  • 20

20 40 60 80

Current (kA) Velocity B Velocity A Current

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ICHSF 2012 2D Axisymmetric Modeling

At the beginning of simulation At the end of simulation

G10 holder Cu 3-turn coil Al tube Axisymmetric axe

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ICHSF 2012 2D Axisymmetric Modeling (Closer look)

Cu 3-turn coil Al tube Axisymmetric axe PDV probe B(10mm away from Probe A) PDV probe A (Middle

  • f 3-turn coil)
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Johnson-Cook Strength Model

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ICHSF 2012

Model for Al 6061-T6 A (MPa) B (MPa) C n m Tm (K) Model 1 [1] 324 114 0.002 0.42 1.34 925 Model 2 [2] 275 500 0.02 0.3 1.0 925 Model 3 [3] 293 121.3 0.002 0.23 1.34 925 Model 4 [4] 289.6 203.4 0.011 0.35 1.34 925

Johnson-Cook strength model was selected, because of high strain rate in electromagnetic forming.

) 1 )( ln 1 )( (

*m n

T C B A − + + = ε ε σ 

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ICHSF 2012 Comparison--- Velocity A (0.8 kJ)

10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 100

Time (micro-second) Velocity (m/s) Model 1 Model 2 Model 3 Model 4 Measurement 1 3 2 4

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ICHSF 2012 Comparison --- Velocity B (0.8 kJ)

5 10 15 20 25 30 35 40 45 50

10 20 30 40 50 60 70 80 90 100

Time (micro-second) Velocity (m/s) Model 1 Model 2 Model 3 Model 4 Measurement

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Strain and Strain Rate for Position A (0.8 kJ)

500 1000 1500 2000 2500 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Time (micro-second) Effective plastic strain rate (/s)

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Effective plastic strain Effective plastic strain rate Effective plastic strain

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ICHSF 2012 Stress-strain Plots for Position A (0.8 kJ)

100 200 300 400 500 600 700 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Effective plastic strain Effective stress (MPa) Model 1 Model 2 Model 3 Model 4 1 2 3 4

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ICHSF 2012 Parameters for J-C model

) 1 )( ln 1 )( (

*m n

T C B A − + + = ε ε σ 

Model for Al 6061-T6 A (MPa) B (MPa) C n m Tm (K) Model 1 324 114 0.002 0.42 1.34 925 Model 2 275 500 0.02 0.3 1.0 925 Model 3 293 121.3 0.002 0.23 1.34 925 Model 4 289.6 203.4 0.011 0.35 1.34 925 (1) Strain rate sensitivity C should be small for Al 6061-T6; (2) Strain hardening has smaller effect than strain rate hardening in this case;

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ICHSF 2012 Summary

1) PDV was applied for the velocity measurement and Ls- dyna electromagnetism module was applied for the simulation of the Al 6061-T6 tube EM expansion; 2) Comparison between the numerical and experimental results showed the good agreement; 3) Four different parameter sets for Johnson-Cook strength model were used in the numerical simulation. The results showed that the value of the strain rate sensitivity for Al 6061-T6 should be small; 4) Strain rate hardening has larger effect in EM expansion;

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ICHSF 2012 Acknowledgement

The authors would like to thank Professor Glenn Daehn and

  • Mr. Geoffrey Taber of the Ohio State University for the

experiment and the velocity measurement using PDV, and Pierre L'eplattenier of Livermore Software Technology Corporation for LS-DYNA software support.

References of J-C strength model parameters:

(1) Corbett, B.: Numerical simulations of target hole diameters for hypervelocity impacts into elevated and room temperature bumpers. International Journal of Impact Engineering 33 (2006), p. 431-440. (2) Elsen, A.; Ludwig, M.; Schaefer, R.; Groche, P.: Fundamentals of EMPT-Welding. Proceedings of 4th International Conference on High Speed Forming, Columbus, OH, 2010, p.117-126. (3) Rule, W.: A numerical scheme for extracting strength model coefficients from Taylor test

  • data. International Journal of Impact Engineering 19 (1997), p.797-810.

(4) Fish, J.: Al 6061-T6 - elastomer impact simulations. Technical report, 2005.

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ICHSF 2012

Questions?