The stand parameter calibrations were used to reduce test data error and to minimize model
prediction error. The test data and its collection methods were carefully examined for possible
sources of error. It was found that the most likely sources of error were in the strip yield stress,
gap, and work roll crown measurements. Two calibrations were performed, one to minimize exit
thickness and rolling load error, the other to minimize strip exit crown error.
The yield-gap calibration varied the strip yield stress and the gap to find a combination which
would minimize the rolling load and exit thickness error. Nine simulations were run representing
a full-factorial two-parameter three-level expansion of three yield stresses and three gaps. From
the results, a response surface of total rolling-load and exit-thickness error was constructed using
quadratic isoparametric interpolation functions. The error over the sample space was minimized
to give the values of yield stress and gap that would minimize the error. This calibration produced
a yield stress of 0.02145 tonne/mm2 and a gap of 3.489 mm. The calibrated yield stress differed
from the test data yield stress of 0.02119 tonne/mm2 by 1.23% and the predicted gap differed
from the test data value of 3.983 mm by 12.40%. These calibrated values were used in the work
roll crown calibration and in the model validation.
The work roll crown calibration attempted to account for the effects of the thermal expansion
on the work roll crown, which affects the strip crown. Five simulations were run with varying
work roll crowns. The error in the strip crown versus the test data was computed and graphed.
The work roll crown that minimized the error was chosen. The calibration gave a work roll crown
of 0.0123 mm which differed from the test data value of -0.16 mm by 107%. While the difference
seems significant with respect to the percent difference, the actual change in crown was only
0.1477 mm and accounts for all thermal expansion of the work roll while rolling the strip.