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Fatigue Crack Growth Rates in Pipeline Steels Using Curved M(T) Specimens



Philippe P. Darcis, John M. Treinen, Joseph D. McColskey


This study presents fatigue data for two different ferrite-pearlite pipeline steels. A fatigue crack growth test for full thickness curved pipeline samples was developed using a Middle Tension, M(T), type specimen. Also, FEA (Finite Element Analyses) were carried out to show the M(T) curvature effects on the fatigue crack growth results. The two steels showed similar fatigue crack growth rate (da/dN) behavior. However, the ferrite-pearlite steel without banding had slightly better fatigue properties than the ferrite-pearlite banded steel. Uncertainty in the fatigue crack growth rates was analyzed by attributing all the fatigue scatter to the Paris law parameter C. The ASTM E647-05 CMOD (Crack Mouth Opening Displacement) vs. a (crack length) relationship does not accurately predict the crack length for the M(T) geometry, leading to conservative fatigue crack growth trends and an overestimation of the true final crack length. The FEA based simulation of CMOD vs. a seems to more accurately predict both fatigue crack growth data and true crack length.
Journal of Testing and Evaluation


crack length measurement, curved middle tension specimen, fatigue crack growth.


Darcis, P. , Treinen, J. and McColskey, J. (2007), Fatigue Crack Growth Rates in Pipeline Steels Using Curved M(T) Specimens, Journal of Testing and Evaluation, [online], (Accessed March 2, 2024)
Created October 22, 2007, Updated October 12, 2021