Hello!
I'm trying to create a model that recreates cyclic compression of a silicon cylinder (hyperelastic). I have the experimental data of a compression until 80% of deformation and have succesfully managed to recreate that model with very good results.

Now I'm trying to recreate the cyclic compression model with mullin's effect added, but the following error appears:

Error in job AmostraA_OgdenN2_Mullin: THE MATERIAL PARAMETERS COULD NOT BE DETERMINED FROM THE UNLOADING TEST DATA. THIS IS DUE TO A SINGULAR DESIGN MATRIX IN THE LEAST SQUARES FITTING PROBLEM.
Error in job AmostraA_OgdenN2_Mullin: CURVE FITTING ALGORITHM FOR MULLINS EFFECT DID NOT CONVERGE.

I have tried to use the calibration tool, to use my data as input to the mullin's effect directly on the material, but i don't understand which data I should use as input for the mullins effect.
I have the data from a single compression until 80% of deformation and the data from cyclic compression ate the same strain rate until 25% of deformation with 4 complete loading-unloading cycles.
I have watched multiple youtube tutorials, read many articles but can't figure this out, i'm just a beginner.

Thank you!