Therefore, the m value thus deduced is not uniquely
determined (not a constant value) but an apparent one
that depends on plastic strain. Accordingly, in order to
remove the strain dependence, the data points are extrapolated
to zero strain and the extrapolated value is
assigned to be m0 for the time being. This m0 is approx.
0.67 which is, in a traditional sense, large enough to
exhibit superplasticity.