Investigation of Rousselier Model and Gurson-Tvergaard-Needleman Model in Ductile Fracture of API X65 Gas Pipeline Steel

Abstract

In this research, the micromechanical Rousselier damage model, which is not available in commercial software is accomplished with a subroutine in Abaqus finite element analysis software. Ductile fracture behavior of API X65 steel is evaluated by simulation of tensile test of smooth and round notch bar specimens of base metal in hoop direction and weld metal. The Rousselier model and its parameters of this model are determined for API X65 steel based on experimental data. In this work, the Rousselier and Gurson damage model is compared for API X65 steel. Results of the tensile test and simulation for the Gurson model show inaccuracy in the final stage of the load-displacement plot. This is because in the Gurson model it is assumed that the fracture surface is flat and shear fracture does not occur in specimens, but in the Rousselier model, the shear fracture is considered. The Rousselier model shows more accurate results compared with experimental data in the final stage of loading. Furthermore, the Rousselier model shows little error comparing with the experiment around maximum load since the void growth due to nucleation is ignored in this model. Also, the Rousselier model shows better convergence when the grooving radius of tensile test specimen increasing but the Gurson model behaves differently.