Civil Engineering Reference
In-Depth Information
the conventional compression tests in Fig.
8.9
, the worked specimen was about 10 °C
hotter than the non-worked specimen. From the profile, the temperatures were identi-
cal at the beginning of the test. Then, the largest difference between tests was near
the middle of the tests. Toward the end of the tests, the temperatures of the worked
and non-worked specimens became close to one another. The same trend was fol-
lowed for the EAF tests in Fig.
8.10
, where the worked and non-worked specimen
temperature profiles were the same at the beginning, they reached their maximum
difference near the middle of the test, and then, the difference between the temper-
atures reduced slightly as the tests came to an end. This divergent then convergent
thermal behavior is a result of the initial dislocation densities in the parts. With the
higher starting dislocation density, the %CW thermal profile increases at a greater
rate in the beginning of the test, whereas the annealed specimen (with a lower dis-
location density) showed a linear increase in temperature. In the middle of the test,
where the %CW specimens were the hottest, conduction heat transfer could be
responsible for the convergence of the %CW and annealed thermal profiles.
The engineering stress-strain plots for the 20 % worked/non-worked tests are
shown below. Specifically, the conventional compression tests are in Fig.
8.11
and
the EAF compression tests are in Fig.
8.12
. Looking at the conventional compres-
sion tests in Fig.
8.11
, one can see that the worked specimens can be distinguished
from the annealed specimens due to the large difference in the flow stress yield
point. However, this difference in flow stress is depleted about halfway through the
testing, and the ending stress for both specimen types is the same. The EAF com-
pression tests in Fig.
8.12
show the same starting difference in stress at the begin-
ning. The difference decreases through the tests, but there is still a recognizable
difference between the stresses of the worked and annealed specimens undergo-
ing these tests. This signifies that the difference in dislocation densities due to the
20 % cold-working was enough to minimally affect the effectiveness of the EAF
technique. The remainder of the mechanical results and discussion is continued in
Appendix C.
From the thermal results, it can be seen that the worked specimens consistently
produced higher thermal profiles compared to the annealed specimens of the same
Fig. 8.11
Stress-strain
profiles (20 %CW/annealed,
conventional compression)
[
5
]. The stress-strain profiles
of the worked specimens are
higher at the beginning of
the test, and by the end of
the tests, both stress-strain
profiles are at the same level
7000
6000
5000
4000
Conv - 20% CW
3000
2000
Conv - 20% Anneal
1000
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Engineering Strain
