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Publication Citation: Crack tip opening angle: applications and developments in the pipeline industry

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Author(s): Elizabeth S. Drexler; Philippe Darcis; Richard J. Fields; Joseph D. McColskey; Christopher N. McCowan; Roni Reuven; Thomas A. Siewert;
Title: Crack tip opening angle: applications and developments in the pipeline industry
Published: July 01, 2009
Abstract: One of the most difficult safety problems associated with gas pipeline to be solved is the control of ductile fracture propagation. To address this issue, the crack tip opening angle (CTOA) criterion is becoming one of the more widely accepted properties for characterizing fully plastic fracture. Our current research has applied the CTOA concept in pipeline characterization. A test technique for direct measurement of CTOA was developed that uses a modified double cantilever beam specimen. In this article, CTOA data on high-strength API X100 pipeline steel are presented. Different optical measurement methods are evaluated, which use the crack edges and the specimen surface grid lines. Crack growth in the base metal and through pipeline girth welds was studied. The effect of specimen thickness on CTOA results was noticeable, with thicker specimens producing a greater resistance to fracture. Finally, the influence of the crack velocity on CTOA material strength was found to be small.
Conference: 12th International Conference on Fracture
Proceedings: Proceedings of the 12th International Conference on Fracture
Pages: 10 pp.
Location: Ottawa, CA
Dates: July 12-17, 2009
Keywords: API X100 steel; crack growth; CTOA; fracture; pipelines; steel
Research Areas: Metals
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