Civil Engineering Reference
In-Depth Information
Fig. 6.14
Strain input
sensitivity for diffuse
deformation model versus
experimental results at first
application of current (60 s)
[
4
]
The following figures show an enlarged portion of the thermal response at sev-
eral times during the test to depict the varying thermal responses from the model
results as compared to the experimental data. Figure
6.14
shows the different model
responses and experimental results during the first application of electricity. As
seen with a decreasing strain input to the diffuse model, this correlates with a lower
thermal profile. This is expected as the cross-sectional area is greater and it has an
inverse correlation with the heat generated within the specimen [i.e., larger cross-
sectional area means less heat generation as described in Eq. (
6.16
)]. As shown, the
experimental results are still less than all of the models, and this is a result of the
deformation still being quite uniform for the experimental test at this point.
In Fig.
6.15
, the same results are seen; however, the experimental results are equiva-
lent to the diffuse deformation model at a 40 % decrease. This is a result of the experi-
mental test having a greater amount of diffuse deformation. For the experimental test,
the deformation along the axial length is diffuse and may not be linearly distributed
from one end of the specimen to the center or at the center point. Thus, the peak tem-
perature may not increase linearly. However, for the model, this is an assumption that
was used when taking the fracture strain measurements from the CGA.
Similar results are presented in Fig.
6.16
, but the experimental result is now at
the diffuse deformation model at 20 % reduction in strain.
The overall conclusion from this analysis is that the sensitivity of the strain
input is not the reason for seeing a larger thermal response from the model that
considers all of the electrical energy is transformed into joule heating. This is
since at the end of the deformation test (i.e., experimental result is near failure),
the experimental result is only at the diffuse deformation model at 20 % reduction
in strain which is a large variation from the original experimental measured strain
data. Thus, this confirms that the observed variation in the thermal responses from
the diffuse deformation model to the experimental result is due to energy going
directly into aiding in deformation (i.e., electroplasticity).
