Platform: All Platforms Applies to: Structural Mechanics Module, Geomechanics Module Versions: All versions

Problem Description

Why do I get the error Failed to compute elastoplastic strain variables when using plasticity/concrete/soil plasticity?

Solution

This happens because the elastoplastic element cannot evaluate a plastic step if the current stress state is outside of the yield surface. There are three typical situations where you may encounter this problem:

In the first load step

The elastoplastic element fails to evaluate the consistence conditions (due to either loads, displacements, initial stress/strains), and it fails to compute the first elastic-predictor step. That is, your initial state, e.g. assumed in-situ stresses in a geomechanical problem are outside the yield surface.

During postprocessing

When results are requested at other positions than the Gauss points, the elastoplastic element actually performs a stress computation. If the gradients of the elastoplastic strains are a large within an element this computation may fail. If this happens, use the Gauss point variables such as solid.sGpx instead of general variables like solid.sx.