I am trying to calibrate a BB-model by using uniaxial cyclic load-unload data (loaded-unloaded for 8 times) at two different strain rates. The strain rates are 0.0008 and 0.0016 1/s. When I import this data into MCalibration, and try to calibrate a BB-model, I get a warning that I should use different strain rates to calibrate the BB-model. When I import that same data and I use 0.01 and 0.1 1/s for the strain rates (just to see if that makes a difference) I do not get this warning. It seems that the initial strain rates (which differ a factor of 2) are too close together to calibrate a BB-model?
Furthermore, I get several warnings that I use monotonic experimental data and that I therefore cannot use Mullins parameters. However, the data I provide is not monotonic loading data, but it consists of load-unload cycles that have been repeated for a total of 8 times.
I have uploaded a figure of one of the two datasets I use. The other dataset is similar but differs in strain rate only.
Anybody can help with this?