Fracture Toughness Characterization of High-Pressure Pipe Girth Welds Using Single-Edge Notched Tension SE(T) Specimens
Enrico Lucon, Timothy S. Weeks, James Gianetto, W. R. Tyson, D. Y. Park
The safety and reliability of large-diameter pipelines for the transport of fluid hydrocarbons is being improved by the development of high-strength steels, advanced weld technologies and strain-based design (SBD) methodologies. Strain-based design imposes a limit on the applied strains rather than the applied stresses. For high-pressure pipelines, SBD requires an assured strength overmatch for the weld metal as compared to the base material, in order to avoid strain localization in the weldment during service. Achieving the required level of strength overmatch, as well as acceptable ductility and low-temperature fracture toughness, is a challenge as the pipe strength increases. Published studies show that low constraint geometries such as Single-Edge Bend, SE(T), or shallow notched Single-Edge Bend, SE(B), specimens represent a better match for the constraint conditions of surface-breaking circumferential cracks in large-diameter pipelines during service . However, the SE(T) geometry is not included in any of the most widely used elastic-plastic fracture mechanics (EPFM) test standards. A procedure has been developed for performing and analyzing SE(T) toughness tests using a single-specimen technique, which includes formulas for calculating J integral and Crack-Tip Opening Displacement (CTOD), as well as estimating crack size using rotation-corrected elastic unloading compliance. Crack-resistance curves and critical toughness values obtained from shallow-crack SE(T) specimens (a0/W = 0.25) are compared to shallow-crack (a0/W = 0.25) SE(B) specimens. We believe that the SE(T) methodology is mature enough to be considered for inclusion in future revisions of EPFM standards such as ASTM E1820 and ISO 12135.
, Weeks, T.
, Gianetto, J.
, Tyson, W.
and Park, D.
Fracture Toughness Characterization of High-Pressure Pipe Girth Welds Using Single-Edge Notched Tension SE(T) Specimens, Materials Performance and Characterization, [online], https://doi.org/10.1520/MPC20130098
(Accessed August 19, 2022)