STP945

    Fatigue Behavior of 5Ni-Cr-Mo-V Steel Weldments Containing Fabrication Discontinuities

    Published: Jan 1988


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    Abstract

    Fabrication discontinuities in weldments pose a serious engineering problem for structural applications involving cyclic loading. Often, the discovery of fabrication discontinuities through nondestructive inspection can pose a dilemma: if not repaired, failure can result from crack initiation and growth; however, if improperly repaired, post-repair discontinuities of even greater severity may result. Thus, rational decision-making criteria are needed to assess the mechanical severity of actual fabrication defects in weldments. This study was undertaken to explore the applicability of linear elastic fracture mechanics to characterize the fatigue behavior of high-strength steel weldments containing lack-of-penetration (LOP) and slag/lack-of-fusion (S/LOF) discontinuities. Full penetration, double-V butt welds with reinforcements removed were tested under zero-to-tension axial loading. Various filler metals and welding techniques were used. Both sound welds and welds containing discontinuities were cycled to failure. Whenever possible, cycles to crack initiation were estimated by strain gage measurements. The fracture mechanics approach was successful in correlating the fatigue lifetimes of specimens containing single LOP discontinuities of varying size. However, the fatigue behavior of specimens containing multiple S/LOF discontinuities proved to be much more complex and difficult to analyze.

    Keywords:

    fatigue, fracture mechanics, welding, discontinuities, lack-of-penetration, slag/lack-of-fusion, 5Ni-Cr-Mo-V steel, fatigue crack initiation, fatigue crack propagation


    Author Information:

    Gill, SJ
    Metallurgist, Fatigue Criteria Section, Material Science and Technology Division, and Mechanical Engineer, Environmental Testing Section, Spacecraft Engineering Department, Naval Research Laboratory, Washington, DC

    Hauser, JA
    Metallurgist, Fatigue Criteria Section, Material Science and Technology Division, and Mechanical Engineer, Environmental Testing Section, Spacecraft Engineering Department, Naval Research Laboratory, Washington, DC

    Crooker, TW
    Program manager for Materials, National Aeronautics and Space Administration, Washington, DC

    Kruse, BJ
    Associate field engineer, Construction Department, Duke Power Company, Catawba Nuclear Project, Clover, SC

    Menon, R
    Research associate and Professor, The University of Tennessee, Knoxville, TN

    Lundin, CD
    Research associate and Professor, The University of Tennessee, Knoxville, TN


    Paper ID: STP23288S

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP23288S


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