For hyperelastic materials, the material Stress/Strain data that is input is the Engineering Stress/Strain. The ANSYS output, on the other hand, is True Stress/Strain. So, the user will need to convert the ANSYS output from True Stress/Strain to Engineering Stress/Strain when comparing the input material curve and output Stress/Strain curves. Formulae to be used: Convert ANSYS Output True Strain to Engineering Strain: Engineering Strain = EXP(True Strain) – 1 Convert ANSYS Output True Stress to Engineering Stress: Engineering Stress = True Stress/(1+Engineering Strain)