Cohesive simulation of hydrogen assisted crack initiation in X70 steel and welded joints

摘要

Fracture mechanics SENT testing and FE modelling to establish hydrogen influenced cohesive parameters for X70 structural steel have been performed. Base metal and weld simulated coarse grained heat affected zone have been included in the study. An example of application of the cohesive model in structural integrity assessments of welded joints have also been carried out. Base metal X70 did not fail at net section stresses lower than 1.29 times the yield strength and revealed low sensitivity to hydrogen embrittlement. Weld simulated coarse grained heat affected zone was prone to fracture at stresses above 70% of the yield strength, which indicates hydrogen embrittlement susceptibility. Cohesive parameters were σ-c=0.3 mm and σ-c=1700 MPa (3.5σ-y) for base metal and σ-c=0.3 mm and v=3900 MPa (4.8·σ-y) for coarse grained heat affected zone.I