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Research Papers

Experimental Investigation of Grain and Specimen Size Effects During Electrical-Assisted Forming

[+] Author and Article Information
Michael S. Siopis

Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824

Brad L. Kinsey1

Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824bkinsey@unh.edu

1

Corresponding author.

J. Manuf. Sci. Eng 132(2), 021004 (Mar 30, 2010) (7 pages) doi:10.1115/1.4001039 History: Received July 15, 2009; Revised January 08, 2010; Published March 30, 2010; Online March 30, 2010

Alternative manufacturing processes such as hot working and electrical-assisted forming (EAF), which involves passing a high density electrical current through the workpiece during deformation, have been shown to increase the potential strain induced in materials and reduce required forces for deformation. While forming at elevated temperatures is common, the EAF process provides more significant improvements in formability without the undesirable effects associated with forming at elevated temperatures. This research investigates the effect of grain size and current density on annealed pure copper during the EAF process. The flow stress reduction effect of the process was shown to decrease with increasing grain sizes. A threshold current density, required to achieve a significant reduction in the flow stresses, becomes more apparent at larger grain sizes, and the value increases with increasing grain size. The effects increase with increasing strain due to dislocations being generated during deformation. Therefore, the dislocation density, related in part by the grain size, appears to be a factor in the EAF process.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

EAF experimental setup

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Figure 2

Example of corrected displacement data for a 2 mm 0 A/mm2 fine grain case

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Figure 3

Experimental and averaged curves for the 1 mm fine grain 0 A/mm2 case

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Figure 4

Reduction in theoretical current density with increasing strain

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Figure 5

2 mm fine and medium grain cases with varying current density

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Figure 6

1 mm fine grain case with varying current density

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Figure 7

0.5 mm fine grain case with varying current density

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Figure 8

1 mm medium grain case with varying current density

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Figure 9

0.5 mm medium grain case with varying current density

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Figure 10

1 mm coarse grain case with varying current density

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Figure 11

0.5 mm coarse grain case with varying current density

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Figure 12

Reduction in flow stress at various strains for the 2 mm 60 A/mm2 case with varying grain size

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Figure 13

Reduction in flow stress at various strains for the 1 mm 60 A/mm2 case with varying grain size

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Figure 14

Reduction in flow stress at various strains for the 1 mm 250 A/mm2 case with varying grain size

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Figure 15

Data scatter magnitude at various strains for the 1 mm 0 A/mm2 case with varying grain size

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Figure 16

Data scatter magnitude at various strains for the 1 mm 60 A/mm2 case with varying grain size

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Figure 17

Data scatter magnitude at various strains for the 1 mm 200 A/mm2 case with varying grain size

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Figure 18

Micrographs of deformed 1 mm coarse grain specimens. Two specimens for the 0 A/mm2 case are shown in (a) and (b), and two specimens for the 250 A/mm2 case are shown in (c) and (d).

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Figure 19

Micrographs and hardness measurements of deformed coarse grain specimens with current densities of (a) 0 A/mm2 and (b) 250 A/mm2

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