Effect of the Luders plateau on the relationship between fracture toughness and constraint for pipeline steels

The effect of Luders plateau on the fracture response of pipeline steels is studied. The study is carried out by using the finite element analysis method combined with the material damage model. The single edge notched bending (SENB) specimens are used, and the complete Gurson model (CGM) is used to simulate the crack growth process. The results show that the Luders plateau has an important effect on the relationship between the fracture toughness and the constraint. When the constraint level is low, the fracture toughness increases with the increase of the Luders plateau length. When the constraint level is high, the fracture toughness decreases with the increase of the Luders plateau length. With the increase of the Luders plateau length, the fracture toughness is more sensitive to the change of the constraint, and the decrease of the fracture toughness with the increase of the constraint is more significant. A constraint-based fracture failure criterion considering the Luders plateau is proposed and validated. The validation results show that the criterion has high accuracy and great application potential to the fracture analysis for pipeline steels with the Luders plateau.