My nonlinear static analysis with bolt preload (2× M4 bolts, 3380N each) fails during the preload step with “integration of the constitutive law” errors and a singular matrix on bolt interface node N154812 (DZ component).
Root cause from the solver log: DEFI_CONTACT contains SANS_GROUP_NO=('master_0', ...) which excludes all 13,073 master surface nodes from contact detection. This results in Nombre de liaisons de contact: 0 on every iteration — no contact pairs ever activate, leaving the bolt halves unconstrained.
Materials are correct (elasto-plastic with valid SY values confirmed in solver input). The issue is purely the contact exclusion generated by SimScale’s code_aster translator.
Could you advise how to avoid this exclusion, or is this a known issue with PENALISATION + bolt preload?