Bilinear steel model with isotropic strain hardening- stl_bl2

This is a uniaxial bilinear stress-strain model characterized by a linear kinematic hardening rule and an optional feature of isotropic hardening which is described by a non-linear rule.

Users have to assign the mean value of steel strength and the mean value minus the standard deviation or the characteristic value in order to describe the mechanical characteristics of the existing or the new material respectively.