Hello, in a fully nonlinear analysis, the inelastic deformations (crack openings, plastic strains, etc.) are typically much more of interest than any stresses (especially after cracking/plastizations start to develop). If you wish a scalar value measuring plastic deformations, look at "Equivalent plastic strain".
For the "Bilinear Steel von Mises" material model, a new data attribute "Mises Equivalent Stress" is available in the current development version now being tested (5.0). If you wish to try the pre-release, please send an email to our general support address, including your ATENA User ID (WR). Mention that you wish to try the "Mises Equivalent Stress".