I have analyzed pure epoxy material with elasto-plastic material properties. I have defined the nonlinear plastic region using eq. plastic strain table. At the end of the analysis I get the global total strain energy (scalar) value but it is less than the real (experimental) value.
The figure below shows the true stress-true strain curves. Blue colored curve belongs to experimental data and the red colored curve belongs to results obtained after FE analysis.
By the way, I used 3D tetrahedron (element 157) for modeling epoxy.
