STP945

    A Study of Plasticity Effects on the Crack Geometry Correction Factors Used with the COD-Design Curve

    Published: Jan 1988


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    Abstract

    A recent application of the COD-Design Curve to fracture data for surface defects in pipeline girth welds, revealed that use of the elastic defect geometry correction factors leads to a nonuniform factor of safety with respect to surface defect aspect ratio. Calculations were performed in this paper which show that the correction factors should be different in the presence of elastic-plastic deformation. This is a possible explanation for the observed nonuniform safety factor. Tabulated solutions based on the elastic-plastic estimation approach for the center cracked panel, single edge notched specimen, and hollow cylinder with internal, complete circumferential crack were used to study the influence of strain on the crack geometry correction factors for long defects. The calculations show that the correction factors must be greater the greater the amount of plasticity. Elastic-plastic finite-element solutions from the literature were used to study the influence of plasticity on the COD-Design Curve correction factors for shorter surface defects.

    Keywords:

    elastic-plastic fracture mechanics, COD-Design Curve, correction factors, pipeline girth weld, surface defects


    Author Information:

    Mayville, RA
    Arthur D. Little, Inc., Cambridge, MA

    Hilton, PD
    Arthur D. Little, Inc., Cambridge, MA


    Paper ID: STP23269S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP23269S


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