Effect of temperature and geometry on the brittle failure of an 18MND5 steel in the lower part of the ductile to brittle transition

Tests on cracked CT and SENT specimens (152 tests) extracted from a nuclear pressure vessel steel (18MND5) were conducted between $-150$ ${}^{\circ }$C and $-50$ ${}^{\circ }$C together with tests on smooth and notched bars. Tests on tensile bars were used to calibrate a temperature-dependent hardening law. Tests on cracked specimens that exhibited brittle failure only were analyzed using the Beremin model. Special care was taken to evaluate local stresses using enhanced mixed finite elements. The Beremin model was able to represent the entire database provided the reference failure stress ${\sigma }_u$ increases with temperature. Finally, the results were also interpreted using the Master Curve approach, which was adapted to account for different stress states using the $Q$-parameter.