Civil Engineering Reference
In-Depth Information
Fig. 11.13
Forming load
recorded for
w
d
=
38.1 mm
[
1
,
2
]. Displayed are the
forming loads for the
classical and two EAB tests
parameters at a die width of
38.1 mm
120
Classical
100
80
60
40
C
d
=
20
Amps/mm
2
C
d
=
30
Amps/mm
2
20
w
d
=
38.1
mm
0
0
2
4
6
8
10
12
14
Position [mm]
Fig. 11.14
Forming load
recorded for
w
d
=
50.8 mm
[
1
,
2
]. Displayed are the
forming loads for the
classical and two EAB tests
parameters at a die width of
50.8 mm
75
Classical
50
25
C
d
=
20
Amps/mm
2
C
d
=
30
Amps/mm
2
w
d
=
50.8
mm
0
0
2
4
6
8
10
12
14
Position [mm]
50.8 mm die width, the 20 A/mm
2
drop-offs were more noticeable and the 30 A/
mm
2
drop-offs were only about twice as large. In Fig.
11.13
, the drop-offs for the
30 A/mm
2
test were larger than those of the 20 A/mm
2
test. However, the aver-
age bending load profile throughout the test remained relatively the same between
the two current densities (note that the load profile was reduced by about 20 N in
comparison with the respective non-pulsed classical test). In Fig.
11.14
, the drop-
offs were again more significant for the higher current density. The bending load
profile produced from the 20 A/mm
2
test showed no notable reduction compared
to the respective classical test, whereas the 30 A/mm
2
test posted a bending load
profile that was about 15 N lower than the conventional load profile. When com-
paring the two figures, the 38.1 mm die width allowed for greater reductions in
the load profile, where both current densities lowered the load profile by 20 N.
However, with the 50.8 mm die width, there may be a type of threshold reached
since the 20 A/mm
2
profile was not reduced compared to the conventional profile,
but the 30 A/mm
2
profile was reduced by about 15 N.
The amount of springback after the test, SB, was determined from Eq. (
11.21
).
SB
=
β
−
β
r
β
·
100
[
%
]
(11.21)
where
β
is the angle at which the specimen was bent (
β
=
180°
−
α
), and
β
r
is the
real angle, measured after the test. The application of electricity during the defor-
mation process resulted in lower springback (up to about a 20 % overall reduction
