Abstract：Constraint effect and fracture behaviour for X100 pipeline steel with axial crack were quantitatively studied by elasticplastic fracture theory combined with FEA. Considering the plastic effects, a parameter βQ was introduced on the basis of J-Q theory and the fracture criterion of J-βQ double parameters was established. The failure curve of X100 was fitted from the data of JR-Δa experiment. Failure pressures for pipelines with internal and external axial cracks were predicted separately. The results show that constraint effect of the external crack is little stronger than the internal crack, but it is opposited when a／δ≤018. For shallow cracks (a／δ≤0.40), crack tip fields are not very constrained and yield failure is most likely to occur as plastic deformation is larger, the failure pressure of pipeline corrosion criterion(PCORRC) is conservative. For deep cracks, strengthened constraint effect results in small plastic deformation and fracture failure will take place.
2011, Vol. 32 
