The toughness and plasticity of steel generally decreases with increasing testing rate. The crack tip opening angle (CTOA) was measured on two types of commercial pipeline steels, API-X65 and API-X100 at a range of displacement rates to characterize rate effects. The testing was conducted at quasi-static and dynamic rates. The crosshead displacements in our test matrix ranged from approximately 0.002 mm/s in the quasi-static mode to 8 m/s in the dynamic mode. The quasi-static tests were conducted in a servo-hydraulic uniaxial test machine using Modified Double Cantilever Beam (MDCB) specimens. The dynamic experiments were made using the same type of specimen and a spring (Belleville) setup on a similar servo-hydraulic uniaxial test machine. The results of these tests indicate that rate effects have minor influence on the CTOA values measured for these materials. The CTOA values measured for the two materials show a small, but convincing differance. The resistance to fracture was found to be higher for the X65 steel. This paper presents results on the influence of displacement rates from quasi-static to dynamic for the X65 and X100 pipeline steels, as well as discussing optimizing the method for CTOA data reduction.
Proceedings Title: Proceedings of the IPC2008: 7th International Pipeline Conference
Conference Dates: September 29-October 3, 2008
Conference Location: Calgary, CA
Conference Title: IPC 2008
Pub Type: Conferences
crack growth velocity, crack tip opening angle, CTOA, pipeline, rate, steel, X65, X100