An experimental investigation was performed to evaluate the applicability of using J-integral resistance (J-R) curves from laboratory specimens to describe the fracture behavior of circumferentially cracked 8 in. diameter ASTM A106 steel pipe. The approach of the study was to perform J-integral tests on 48 in. long, 8 in. diameter, Schedule 80 ASTM A106 steel pipes and compare them with J-integral tests performed on 1/2T, 1T plan, and 2T plan compact specimens machined from the pipe wall. The pipes were tested in four-point bending and were monitored for load, crack opening displacement, bend angle, and electrical potential drop. Elastic compliance and direct-current potential drop (DCPD) techniques were used simultaneously to predict crack length during the tests. The compact tension specimens were tested in a conventional screw-driven testing machine while being monitored for load, load-line deflection, and electrical potential drop. Elastic compliance and DCPD techniques were also used for crack length predictions during these tests.

The results of this series of J-integral tests indicate that similar J-R curves result from the two types of specimens. However, small specimen tests cannot easily be used to predict full J-R curve behavior for larger, full-sized specimens owing to the modest amount of crack extension available in laboratory-sized specimens.