Dyna-material capable of negative plastic strains?

[MaddogMcCree]

Is there a material model in LS-Dyna which can deal with plastic tangent moduli higher than the elastic young´s modulus?

An increase in material stiffness results in negative plastic true strains. Using it as input for MAT_24, negative plastic true strains are ignored and set to zero.

Can you propose a material model to me? Maybe a rubber-like one, as rubbers can also show an increase in stiffness.

Thanks a lot,
Maddog