The application of High-Strength Low-Alloy steels (HSLA) in constructions is hindered by traditional design rules. HSLA steels, however, offer huge ductile resources as proven by numerical studies of (Bri17) on a modified Gurson-Tvergaard-Needleman model (GTN). Yet, previous studies on this topic did not consider cleavage fracture, which is necessary for a full prediction of the materials behavior, including the brittle material properties.
Up to now, cleavage fracture in Gurson models is mostly simulated by a combination with a Beremin model (Pin08). The major drawback of the Beremin model is the limitation of applicability to post-processing. This leads to the fact that inverse transition behavior of ductile failure and cleavage fracture cannot be predicted.
An extended Orowan cleavage fracture criterion defines failure in dependence of critical stress- and strain states for a single element (He17). By using this single element formulation, transition zone behavior can be well predicted as cleavage fracture and ductile failure mechanism are coupled in the material model. However, the extended Orowan criterion is not implemented in any Gurson model yet.
This study aims at evaluating and implementing a suitable cleavage fracture criterion for a GTN model to model the transition behavior of HSLA steels. Thus, the extended Orowan criterion given by (He17) was implemented into a Gurson model. A brief overview of the extended Orowan criterion and a summary of its implementation to a GTN model is given. The discussion of the influence of stress triaxialities and plastic strains on cleavage fracture as well as the experimental calibration scheme are further important aspects of this study. Thereby, this study supports the structural application of HSLA steels trough a better prediction of the transition behavior, as both ductile failure and cleavage fracture properties must be considered in design of structures made of HSLA steel.