J-Integral resistance curves of a high-strength steel pipe base metal were measured using a single-specimen technique with clamped singleedge tension (SE(T)) specimens. The procedure is described in a format similar to that of ASTM E 1820-06 for single-edge bend (SE(B)) and compact tension (C(T)) specimens. The equations used, including those for evaluation of J-integrals from the area under load/plastic crack mouth opening displacement (CMOD) curves, and evaluation of crack size from CMOD unloading compliance including correction for rotation, were developed using finite element analysis (FEA) for specimens with a height to width ratio H/W=10. Compliance and rotation correction equations are valid for 0.05≤a/W≤0.95 and 0.1≤a/W≤0.7 respectively, and stress intensity factor equations for 0.05≤a/W≤0.95. J-integral equations are valid for 0.05≤a/W≤0.7 except for the crack growth correction parameter γ that is valid for 0.1≤a/W≤0.7. Some details of the tests, such as the loading procedure used for initial crack estimation, are also discussed and compared with those recommended for SE(B) specimens. The initial and final crack sizes evaluated using the unloading compliance technique are compared with those using the nine-point optical technique on broken specimens. J-Integral resistance curves measured using clamped SE(T) specimens and conventional SE(B) specimens, both plain-sided and side-grooved with shallow and deep cracks, are reported and compared.
Pipelines are increasingly required to have adequate resistance to large deformations such as caused by ground movement. In response to this, "strain-based design" has been developed to enable assessment of imperfections at applied strains beyond yield. In addition, it is proposed to take advantage of the increased apparent toughness under low constraint, appropriate for defects such as girth weld imperfections in pipe under axial tension, compared with the high-constraint toughness measured in conventional tests such as ASTM E 1820-06. This has been advantageously applied in offshore pipeline projects.
