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A recent series of large-scale, high-energy dynamic degraded piping experiments, conducted for the International Piping Integrity Research Group (IPIRG), are evaluated to determine the ability of modern structural and fracture analysis computational tools to predict the dynamic response and failure mode of prototypical piping systems with degraded sections. Results are also useful in confirming leak-before-break principles. This paper assesses the IPIRG 1.3 test series failure mode(s) for austenitic and ferritic base and weld metal test sections under severe dynamic loading conditions. Small-scale test specimen data are used to perform limit load, ductile tearing, and low-cycle fatigue calculations at 288°C, and calculated results are compared to data from five large-scale pressurized piping system experiments with circumferential interior flaws. Experimental behavior and fractographic evidence are also described.
The dominant prepenetration failure mechanism for the IPIRG 1.3 experiments was not lowcycle flaw growth, but another mechanism such as ductile tearing followed by instability.
time-dependent fracture, ductile tearing, aged-cast piping, strain rate effects, austenitic stainless steels, ferritic steels
Senior consultant, Applied Science & Technology, Poway, CA
Staff engineer, Robert L. Cloud & Associates, Inc., Berkeley, CA