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    Fatigue Enhancement of Undersized, Drilled Crack-Arrest Holes

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    Simmons_ku_0099D_13074_DATA_1.pdf (27.55Mb)
    Issue Date
    2013-12-31
    Author
    Simmons, Gary Gene
    Publisher
    University of Kansas
    Format
    497 pages
    Type
    Dissertation
    Degree Level
    Ph.D.
    Discipline
    Civil, Environmental, & Architectural Engineering
    Rights
    This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
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    Abstract
    Fatigue cracks occur in steel bridges from repeated loads. If allowed to continue to grow, eventually the fatigue cracks will require either expensive repairs or reduction of traffic loads on the bridge, or they may lead to the failure of the bridge. The objective of this research was to develop a new, cost-effective technique that can be used to arrest the growth of fatigue cracks before they develop to an extent that more expensive repairs are required. It is well known that drilling a hole (crack-stop hole) at each end of a fatigue crack can arrest the growth of the fatigue crack. This new technique consisted of cold-expanding a crack-arrest hole thereby cold-working the material around the hole and subjecting the cold-worked material to ultrasonic vibration. It was hypothesized that this process would increase fatigue crack initiation life three ways. First, the compressive force used to cold-expand the hole would result in residual compressive stress fields around the hole when the radial force was removed. Second, the cold-expansion would cause strain-hardening and cold-working with a concomitant increase in the yield and ultimate strengths of the steel. Third, the ultrasonic vibration from the PICK treatment would further increase the resistance to fatigue propagation by increasing the yield and ultimate strengths and increasing the radial extent of the residual compressive stress field. These expected results and their effects on fatigue crack initiation were investigated through a proof-of-concept testing program using reduced-scale, laboratory models and by mathematical modeling.
    URI
    http://hdl.handle.net/1808/12961
    Collections
    • Engineering Dissertations and Theses [1055]
    • Dissertations [4473]

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    Contact KU ScholarWorks
    785-864-8983
    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    Image Credits
     

     

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