Constraint corrected cleavage fracture assessment based on tests of standard and small scale cruciform specimens

The objective of the present study is the determination and validation of a constraint corrected probabilistic cleavage fracture model considering both, the nucleation and the possible instability of potentially critical microdefects. For this purpose, the local mechanical conditions at the cleavage triggering point are analyzed by a numerical simulation of different fracture mechanics experiments using C(T), M(T) and SE(B) specimens with deep and shallow cracks. The data base is extended by experiments on novel small scale cruciform bending specimens allowing the application of an additional stress acting longitudinally to the crack front. Based on the results, an enhanced local cleavage fracture model is proposed, which accounts for the nucleation of microdefects in terms of a combined p arameter of the local accumulated plastic strain and the local stress triaxiality ratio.