Civil Engineering Reference
In-Depth Information
Fig. 8.5
True stress-strain
profiles for EAF tests
at CD
=
15 A/mm
2
[
5
].
As was the case with the
conventional compression
stress-strain profiles, the
stress-strain profiles for the
EAF test also showed no
difference
1200
1000
800
600
15.08 m, 21.99 m,
m
µ
µ
and 27.20
µ
400
200
0
0
0.2
0.4
0.6
0.8
1
1.2
True Strain
Figure
8.5
depicts true stress-strain profiles for EAF tests with a starting cur-
rent density of 15 A/mm
2
. All of the profiles were the same, thus signifying no
relation with the different grain sizes tested.
8.1.3 EAF/Grain Size Conclusions
The differences between the grain sizes did not have an effect on the stress-strain
profiles of the conventional compression and the EAF compression tests under
these conditions. Additionally, there was only about a 15 °C difference in the ther-
mal profiles (stationary electrical and EAF compression) between the largest grain
size and the other two grain sizes; however, this was a very minor difference and
this did not have any effect on the mechanical performance during the EAF tests.
Work by Siopis et al. examined the effect of different grain sizes on EAF compres-
sion at the micro-level [
6
]. In this work, specimens with a diameter of up to 2 mm,
with grain sizes from 9 to 276 µm, were compressed, while electrical power was
applied. This work showed that the difference in the grains, at the micro-level, did
affect the EAF technique, in that as the grain size increased, the electrical thresh-
old current density increased.
8.2 Prior Cold Work Effect on EAF
Within this section, the relationship between dislocation density and efficiency of
EAF is explored. Since the starting grain sizes in the previous section were not dif-
ferent enough to produce experimental trends, the focus was shifted toward exam-
ining the effect of prior cold work in the specimens. As the cold work is increased
in a metal, the dislocation density within that metal will increase, thus leading
to a greater amount of obstacles which moving dislocations will have to surpass
