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Monday 25 September 2006
DUCTILE FRACTURE CONTROL FOR HIGH STRENGTH STEEL PIPELINES
A. Fonzo, A. Meleddu, G. Demofonti, M. Tavassi , B.Rothwell
*(TransCanada)
Referee: A. Mazzarano, A. Podrini
Paper presented to: 6th International Pipeline Conference, IPC 2006
Calgary, Alberta, 25-29, September 2006
The determination of the toughness values required for arresting ductile fracture propagation has been historically based on the use of models whose resulting predictions can be very unreliable when applied to new high strength linepipe materials (≥X100) and/or different operating conditions. In addition, for the modern high strength steels a methodology for determining the material fracture resistance for arresting running shear fracture starting from laboratory data is still lacking.
The work here presented (developed within a PRCI sponsored project) deals with the use of CSM’s proprietary PICPRO® Finite Element code to develop methodologies for ductile fracture propagation control in high grade steel pipes. The relationships providing the maximum crack driving force which can be experienced in a pipe operated at known conditions have been determined, for different mixtures of gas. On the other side, an empirical relationship has been found to correlate the critical Crack Tip Opening Angle (CTOA) determined by laboratory testing, to the critical CTOA on pipe (which represents the material fracture propagation resistance) with the aid of devoted simulations of past full-scale burst tests. By comparing Driving Force and Resistance Force, ductile fracture control for high strength steel pipelines can be achieved.
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