Civil Engineering Reference
In-Depth Information
Fig. 6.37
Stress reduction difference during current application between experiment and model
simulation for PS 4
against bulk heating effects as a result of the diffuse thermal output from the ther-
mal modeling section being used. The division of bulk heating and the electroplastic
effect will be accounted for in the subsequent thermo-mechanical modeling section.
Additional error may be due to the initial linear strain input used in the diffuse defor-
mation thermal model to produce the thermal response applied in this modeling sec-
tion. To physically quantify the difference in flow stress reduction, Fig.
6.37
displays the
difference in the flow stress reduction between the experimental result and the model
result. The difference in the flow stress reduction is nearly constant for each electrical
pulse with an average of 27 MPa. Thus, it is assumed to be a result of thermal expansion
stress which was not considered in this model. The flow stress reduction due to ther-
mal expansion is incorporated in the thermo-mechanical model in the next section. As
a result of thermal expansion not being incorporated in the model, the simulation pre-
dicts a greater material flow stress as compared to the experimental result. The model
exceeds the point at which the experimental result failed due to the lack of failure crite-
ria applied to the model simulation.
6.2.4 Mechanical Modeling Conclusions
The flow behavior in uniaxial tension is one key aspect to understanding the
macro-material properties of sheet metal subject to electric current flow during
deformation. As a result, this section examined the local material strain and stress
by incorporating both a structural and geometric non-homogeneity in the sheet
material. The model in this section was capable of predicting the flow behavior
and instability strain of sheet forming at room temperature and at constant elevated
temperatures. For non-uniform temperature distributions as in EAF, the model
was capable of predicting the incremental strains throughout the sheet sample and
