Answer:
When calculating nonlinear material models (especially for plastic material models), the calculation is always related to the original constant internal forces. Therefore, the smoothing of the FE elements should be set to "Constant" (see Image 01).
Furthermore, the stresses are related to the principal stresses σ1 or σ2
Even if these conditions are taken into account, deviations from the defined limit stress may occur. They usually result from the defined hardening modulus. This fact is explained in detail in this technical article, which can be found under the links.
