Why do I get underestimated strain energy values in the plastic region?

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.

In the elastic region curves almost coincide but in the plastic region there is huge strain energy difference.

By the way, I used 3D tetrahedron (element 157) for modeling epoxy.

0 Zach Fata over 3 years ago

The discrepancy could be in the material characterization. The FE results appear to yield before the experimental results. Are you confident in this material characterization? Have you correlated any other test results?
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0 Palm_Tree over 3 years ago

Dear Zach Fata,

Thank you for your reply,

What do you mean by material characterization?

Actually, FE result yields at the strain value where I initiated plasticity. Until that point (true) stress-strain values are almost the same. I am definig plasticity at the beginnig of non-linear region by using table. I have also added some of my analysis screenshots. May be it will be helpful for you to spot the mistake.
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0 Zach Fata over 3 years ago

By material characterization, I am referring to how well the material parameters entered into mentat reflect the true material used in the experiment. Based just on the information you have provided, it appears your yield point is not correct.
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