Phenomenological 2D and 3D Models of Ductile Fracture for Girth Weld of X80 Pipeline

Welding is the main method for oil/gas steel pipeline connection, and a large number of girth welds are weak part pipeline. Under extremely complex loads, undergoes significant plastic deformations eventually leads to fracture. A damage mechanics model promising approach, capable describing material fracture problems according stress states materials. In this study, an uncoupled 2D with function strain triaxiality, two 3D models, consider effect Lode parameter stress-modified critical (LSMCS) model, extended Rice–Tracey (ERT) criterion were applied X80 welds. Comprehensive experimental research was conducted on different notched specimens, covering wide range states, corresponding finite element models established. phenomenon-based hybrid numerical–experimental calibration also determine these three triaxiality influence law tensile strength analyzed. The results showed that proposed could better characterize ductile behaviors pipeline; however, prediction accuracy higher than model. functional relationship between satisfied distribution form quadratic increased monotonically. can be used predict under various loads.