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Thermally-Enhanced Forming of Mg Sheets Midterm Report, Dec. 5, 2008 - May 31, 2009

Thermally-Enhanced Forming of Mg Sheets Midterm Report, Dec. 5, 2008 - May 31, 2009. Robert H. Wagoner R. Wagoner, LLC 144 Valley Run Place Powell OH 43065. One-Year Project Goals (from Research Agreement, signed December 5, 2008).

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Thermally-Enhanced Forming of Mg Sheets Midterm Report, Dec. 5, 2008 - May 31, 2009

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  1. Thermally-Enhanced Forming of Mg SheetsMidterm Report, Dec. 5, 2008 - May 31, 2009 Robert H. WagonerR. Wagoner, LLC144 Valley Run PlacePowell OH 43065

  2. One-Year Project Goals(from Research Agreement, signed December 5, 2008) • Task “1.Formulate a simple, approximate, constitutive equation based on simple testing temperature at a range of temperatures, rates and strains that is suitable for implementation in commercial sheet-forming softward (LS-Dyna, PamStamp, etc.). ” • Status: First fitting completed. (For Posco AZ31B material provided.) To be improved. • Task “2.Develop a thermo-mechanical FE model of a simplified sample part to be specified by Posco.” • Status: The simplified model has been constructed in Abaqus and preliminary testing has been done. Will perform simulations using Abaqus for comparison with Posco simulation using LS-Dyna or PamStamp. Will refine thermal model. • Task “3.Using the constitutive equation of Goal 2 and the FE model of Goal 3, identify optimal thermally-assisted forming strategies for the sample part.” • Status: Not started yet.

  3. Summary Task I. Constitutive Equation Measurement -A. Tensile testing – AUSTEM Mg AZ31B -B. Screening of material (use 118-5) -C. Tensile testing - Posco Mg AZ31B -D. Fitting to 3 laws: H, V, H&V -E. Test with FEA simulation Task II. Postech/Posco Formability Test Simulation -A. Put in ABAQUS model -B. Modify B.C. for convergence -C. Preliminary simulation using Posco/Postech constitutive eq* * K. Oh and et al., “Development of New Formability Test for Sheet Materials using Axiomatic Design”, submitted to J. Mater. Proc. Tech..

  4. Summary of Properties of Mg sheets material used

  5. Tensile Test Results:AUSTEM vs. Posco Mg AZ31B

  6. Tensile Tests of Mg AZ31B at 150oC & 200oC

  7. Tensile Tests of Mg AZ31B at 250oC & 300oC

  8. Tensile Test Results: Posco Mg AZ31B

  9. Tensile Tests of Mg AZ31B at 10-1/s & 10-2.5/s

  10. Tensile Test of Mg AZ31B at 10-4/s

  11. Constitutive Equation Framework = 3 choices Hollomon: Voce: H / V: Three versions: # Parameters (h(T) w/1 parameter) 1) Hollomon: 4 2) Voce: 5 3) H / V: 8

  12. Fitting Procedure Least squares fit to 4, 5, or 8 parameters, using tensile data from 0.02 – Software: SigmaPlot Starting parameters were varied in this order: K1, K2 = 50, 100, …, 1000 n = 0.05, 0.06, …, 0.5 m = 0.05, 0.06, …, 0.2 B = 0.01, 0.05,…, 0.5 C = 5, 10, …, 200 = 0.1, 0.2, …,1 = 0.1, 0.2, …,1 Least squares fit => K1, n, m, K2, B, C, , (smallest standard dev.)

  13. Choice of Temperature Function h(T) “T-1” “T-2” “T-exp”

  14. Least-Squares Fits (Current Best Eq.)

  15. Fitting of Tensile Test at 150oC & 200oC

  16. Fitting of Tensile Test at 250oC & 300oC

  17. Test of Best-Fit Constitutive Equations Tensile test simulations: • FEM model, using ABAQUS software • Uniform temperature distribution • Solid element: C3D8R • Material property: Voce Law – (T-2)

  18. Tensile test of Mg AZ31B – Voce (T-2)

  19. Tensile test of Mg AZ31B – Voce (T-2)

  20. PosTech / Posco Formability Test Simulation

  21. Simulation of Stamping Process • ABAQUS/Standard • Material: 340BH* • Thickness = 0.738 mm • * • Contact: • Friction coefficient: 0.15* • The z-coordinates of the nodes in • blankholder which were not 0 were • changed to 0. • K. Oh and et al., Development of New Formability Test for Sheet Materials • using Axiomatic Design, J. Mater. Proc. Tech. (submitted)

  22. Current Results vs. Oh paper*, Fig. 14 D D C A A C B Oh paper* Fig. 14(c) B Current results Minor strain distribution Holding force = 300kN Drawing depth = 60 mm • K. Oh and et al., Development of New Formability Test for Sheet Materials • using Axiomatic Design, J. Mater. Proc. Tech. (submitted)

  23. Current Results vs. Oh paper*, Fig. 14 B B C C A A Oh paper* Fig. 14(c) D D Current results Minor strain distribution Holding force = 300kN Drawing depth = 60 mm • K. Oh and et al., Development of New Formability Test for Sheet Materials • using Axiomatic Design, J. Mater. Proc. Tech. (submitted)

  24. Current Results vs. Oh paper*, Fig. 9 D D A A C C B B To be compared with Fig. 9 (a)* To be compared with Fig. 9 (a)* Thickness distribution Holding force = 100kN Drawing depth = 30 mm Thickness distribution Holding force = 300kN Drawing depth = 30 mm • K. Oh and et al., Development of New Formability Test for Sheet Materials • using Axiomatic Design, J. Mater. Proc. Tech. (submitted)

  25. Current Results and Oh paper*, Fig. 9 D A C B To be compared with data for Fig. 9 (c)* Thickness distribution Holding force = 500kN Drawing depth = 30 mm • K. Oh and et al., Development of New Formability Test for Sheet Materials • using Axiomatic Design, J. Mater. Proc. Tech. (submitted)

  26. Note R. Wagoner LLC requests the original Oh data* for Figure 9 and possibly other draw depths and variables (thickness strain, von Mises strain) for comparison with current results. Also, as shown on the next slide, punch force vs. draw depths could be compared. The paper does not clearly show those results. • K. Oh and et al., Development of New Formability Test for Sheet Materials • using Axiomatic Design, J. Mater. Proc. Tech. (submitted)

  27. Punch Force vs. Draw Depth * K. Oh and et al., “Development of New Formability Test for Sheet Materials using Axiomatic Design”, submitted to J. Mater. Proc. Tech..

  28. Conclusions • Tensile tests of Posco Mg AZ31B have been carried out, 150oC - 300oC, 10-1/s - 10-4/s. • A preliminary constitutive model reproduces measured tensile data with reasonable accuracy (<s> = 7 MPa) • Further refinement of constitutive model is needed to reproduce • large-strain tensile response better. • The Oh formability test has been implemented and tested using Abaqus (material: 340BH). • Additional data from Oh simulations are requested to permit additional verification. * K. Oh and et al., “Development of New Formability Test for Sheet Materials using Axiomatic Design”, submitted to J. Mater. Proc. Tech..

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