Consideration of Constraint Effect in Fracture Mechanics Assessment for a Vessel Low Alloy Steel

Abstract Numerous fracture tests have been performed by EDF and Framatome on various specimen’s geometry extracted from a 18MND5 ferritic steel plate, in the brittle-to-ductile transition regime. C(T), SE(T), SE(B), and non-standard specimens have been tested. This database has been recently updated with SE(T) tests performed in the lower shelf of the transition domain. This work highlights a robust methodology which allows to predict constraint effect with minor consequences of the choices of the Weibull stress model formulation (classic model, consideration of stress threshold...) and on m parameter on the final interpretation. A local approach based deterministic industrial method is proposed to consider this effect in Engineering Fracture Mechanics Assessment without considering any probability of failure or statistical approach. It allows to evaluate constraint effect at discrete locations along the crack tip. Its application on industrial cases shows that parameters set have limited impact on constraint effect prediction.