Civil Engineering Reference
In-Depth Information
Fig. 11.18
Springback
reduction for various pulse
duration [
1
,
2
]. Percent of
springback reduction in
relation to the duration of
each electrical pulse (constant
pulse period, die width, and
current density)
80
60
40
w
d
=
38.1
mm
c
d
=
30
Amps/mm
2
20
0
0
1
2
3
Pulse Duration [s]
electrical tests. Also, there was only about a 5-10 N difference in flow stress drop-
offs between the 20 and 30 A/mm
2
tests, with the 30 A/mm
2
test producing the
larger drop-offs.
The percent of springback reduction as a function of pulse duration can be
shown in Fig.
11.18
. For this graph, a constant current density of 30 A/mm
2
, die
width of 38.1 mm, and pulse period of 30 s were used. The percent reduction in
springback is significantly dependent on the length of the pulse duration. Of note
is that, using a pulse duration of 3 s, and pulsing every 30 s during deformation,
about 77 % of the total springback can be removed from the specimens.
11.1.9.3 Effect of Pulse Period
The following figures help to illustrate how different pulse periods (time in
between successive electrical pulses) can influence bending load and springback.
Figure
11.19
displays plots of load versus position data where a constant current
density of 30 A/mm
2
, a constant pulse duration of 2 s, and constant die width of
38.1 mm were maintained while pulse periods of 20 and 30 s were utilized. The
flow stress was reduced by about 5-10 N for the 30-s pulse-period test and by about
15-20 N for the 20-s pulse period test, when compared to the classical test. The
more frequent pulses of the 20-s-period test provided for a slightly lower flow stress
profile compared to the 30-s-period test. Additionally, the drop-off magnitudes of
Fig. 11.19
EAB forming
loads for different pulse
periods [
1
,
2
]. Forming load
profiles are presented which
represent a 20 and 30 s pulse
period in between successive
electrical pulses (constant
pulse duration, die width, and
current density)
120
Classical
100
80
60
40
p =
20
sec
20
p =
30
sec
C
d
=
30
Amps/mm
2
0
0
2
4
6
8
10
12
14
Position [mm]
