Background

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Background
Mg AZ31B sheet alloy has advantages of low
density, high strength and high stiffness.
However, it has limited formability at room
temperature, and unknown behavior at complex
forming conditions, especially in the
thermoforming process. The objective of
this research is 1) Design and optimize test
devices for elevated-temperature tension /
compression (T / C) of sheet metal alloys 2)
Measure T / C plastic hardening curves for Mg
AZ31B sheet 3) Develop constitutive laws for
Mg AZ31B sheet alloys (0.1/s-10-4/s,
150oC-300oC) 4) Simulate thermo-assistant
deep drawing of Mg AZ31B, enhancing formability
using non-isothermal heating strategies
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Sheet Tension / Compression Test Room Temperature
Mg AZ31B, O-temper, 3.2mm
Boger et al., Int. J. Plast., 2005
Lou et al., Int. J. Plast., 2007
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Sheet Tension / Compression Test Elevated
Temperature
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Sheet Tension / Compression Test Elevated
Temperature
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Constitutive Equations, 150oC-300oC Mg AZ31B 1mm
sheet
M1 lt7MPagt
M2opt lt4MPagt
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Thermo Deep Drawing
Uniform Temperature
150oC-300oC

• Axisymmetric
• Material Model M2opt
• Friction coeffcient 0.08
• Fix the positions of blank holder and die
• Finer Mesh in the corner of punch and die
• Velocity of punch 10, 1, and 0.1 mm/s

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Thermo Deep Drawing
R60mm, Punch speed 1mm/s Failure criteria
thickness strain -0.2
150oC-300oC

150oC
LDR Di/Df (Depth) 10mm/s 1mm/s 0.1mm/s
150oC 1.9 (38mm) 1.9 (37mm) 1.9 (37mm)
200oC 1.9 (38mm) 1.9 (37mm) 1.9 (37mm)
250oC 1.9 (38mm) 1.9 (37mm) 1.8 (36mm)
300oC 1.9 (38mm) 1.9 (37mm) 1.8 (35mm)
150oC-200oC 2.3 (58mm) 2.2 (49mm) 2.2 (49mm)
150oC-250oC 2.4 (63mm) 2.6 (72mm) 2.6 (73mm)
150oC-300oC 3.2 (121mm) 3.2 (123mm) 3.3 (125mm)
Diameter of finished cup Df 55.2mm
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Conclusions

• Develop high-temperature T/C device
• Temperature range RT - 450oC
• DT (Gage Length) lt 8oC
• Heating time 10 minutes for 250oC

• High Temperature T/C testing of Mg AZ31B sheet
• Inflected flow (twinning) disappears between
  130oC - 140oC

• Constitutive equations for Mg AZ31B sheet
• Experiments, numerical fitting and FEA
  verification
• 150oC - 300oC, 0.1-10-4/s, standard deviation
  4MPa

• Thermo-assistant deep drawing
• Non-isothermal heating improve the LDR from 1.9
  to 3.3

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Mg AZ31B Sheet Formability Experiment and
Simulation K. Piao and R. H. Wagoner Department
of Materials Science and Engineering, The Ohio
State University