Radioss Validation Study: new post-criteria behaviors for /FAIL/JOHNSON
Altair EmployeeWhen it comes to metal or plastic damage, /FAIL/JOHNSON is a widely used, efficient failure model. This failure model uses a nonlinear, plastic strain-based, failure criteria with linear damage accumulation.
After the failure criteria is reached, some specific treatments can be applied to the solid elements through the parameter Ifail_so.
Until version 2024.1, only the following options were available:
- If Ifail_so=1, solid element is deleted when D=1 for 1 integration point
- If Ifail_so=2, for each integration point, the deviatoric stress tensor vanishes when D=1.
In Radioss 2025, new values for Ifail_so are being introduced:
- If Ifail_so=3, for each integration point, the deviatoric stress tensor vanishes and pressure can only be positive or null.
- If Ifail_so=4, for each integration point, the whole stress tensor vanishes.
The following pdf document is the validation report of these new features:
In summary, the following ballistic model highlights quite well the positive effect of Ifail_so=3.
Here are 2 of the demo models you can use to test these new features:
Do not hesitate to test these new features and provide us some feedbacks!