With unknown you can set which unknown will be used for deciding if an element should be refined. The size of the unknown field will be used.
Possibilities for unknown are: -materi_damage, -materi_displacement, -materi_plasti_kappa, -materi_strain_elasti, -materi_strain_plasti, -materi_strain_total, -materi_stress, -materi_velocity, -materi_void_fraction and -residue.
As a special option you can set unknown to -nothing; then an element is refined always.
For finding localization zones (e.g. shear bands) choosing -materi_strain_plasti or -materi_damage seems to be most robust.