Vinayak Vipradas
Ansys Employee
Multilinear Isotropic Hardening is defined by Plastic Strain vs True Stress, where the first point indicates the onset of Plastic Deformation which is (0, yield strength). The first point in the table is at zero plastic strain and stress at the yield point. The stress-strain curve should be monotonically increasing so the negative slope of stress-strain data should be discarded.
For a detailed explanation on data points for defining Multilinear Hardening, please refer to this link:
Defining a Multilinear Plasticity Hardening Model in Ansys Mechanical - YouTube

Thank you,