Civil Engineering Reference
In-Depth Information
• The eficiency of the applied electrical parameters must be considered because
the same amounts of formability improvements may be possible from less pow-
erful electrical input parameter combinations.
11.4.3 Non-uniform Deformation (E.G. Channel Formation)
The majority of EAM research has been conducted on processes where uniform and
uniaxial deformations were taking place. However, this work researched the effect
of the EAM technique on a non-uniform channel formation process using Al5052-O
sheet strip specimens [
23
]. The experimental setup can be seen in Fig.
11.45
, includ-
ing the custom insulated EAM channel die supplied by the Ford Motor Company.
The EAM variables which were examined in this work are current density,
pulse duration, pulse period, and die speed. Specifically, the Al5052 sheet strip
specimens were formed into channels using the EAM technique and experiments
were run with different combinations of the variables mentioned above.
Engineering stress versus elongation plots examining the effects of either pulse
period or pulse duration can be seen in Fig.
11.46
(parts a and b). In part a for this
particular current density magnitude, it can be seen that the length of the pulse
period had little effect on the increased elongation. However, in part b, a longer
pulse duration (2 s) was proved to be overly powerful and led to premature failure
compared to non-EAM baseline channel forming.
Conclusions from this work are as follows:
• EAM parameter combinations above the threshold can improve the part elonga-
tion and reduce the forming forces.
• Additionally, the magnitude of each of the electrical variables must be propor-
tionally “balanced” for best results.
Ceramic Top Plunger
Specimen
Clamp
Bottom Die
Bottom Insulation
Fig. 11.45
EAM channel formation experimental test setup [
23
]. This setup included a 2-part
channel die, composed of a top ceramic plunger and a metal bottom portion with insulation inte-
grated into the base structure
