Civil Engineering Reference
In-Depth Information
(a)
100A/mm
2
(b)
120A/mm
2
Effect of Pulse Period
Effect of Pulse Duration
-
-
Fig. 11.46
EAM channel formation formability results [
23
]. EAM was not as effective with
channel forming as uniaxial tension, because channel forming caused localized deformation
regions, whereas uniaxial tension consisted of uniform deformation.
a
Engineering stress-elon-
gation profiles for CD
=
100 A/mm
2
with varying pulse periods.
b
Engineering stress-elongation
profiles for CD
=
120 A/mm
2
with varying pulse durations
• When dealing with localized strain regions, such as with channel forming, it is
no longer optimum to apply the electricity throughout the entire part, but rather
to devise a method to divert the electricity to primarily the regions of localized
strain, which need it most.
• When examining the effects of die speed, it can be concluded that there is a
relationship between the strain-rate sensitivity of the Al5052-O alloy and the
electricity's sensitivity.
• As the current density is increased, the longer durations and more frequent
pulse periods can be detrimental to the overall formability of the specimen, even
if they do reduce required deformation forces in the process.
11.4.4 Springback Reduction Using EAF
Springback can be a big concern when metal forming. Currently, springback is
reduced by costly trial-and-error processes or by slow and intensive modeling
strategies. In 2009, Green et al. examined the effectiveness of applied electricity
when reducing springback in formed sheet metal specimens. In this work, Al6111
sheet strips were used. Specifically, shape retention testing was performed, in
which the sheet strip specimens were bent around a round die, clamped in place,
and then a single pulse of electricity was applied. Immediately after the pulse of
electricity, the clamps were removed and the springback was measured.
Current density and duration of the single pulse were varied as part of this
research. Figure
11.47
shows the amount of springback reduction that was achieved
from this work 0. From the figure, for a single 1.5-s-long electrical pulse, the
