STP927: Effect of Load Transfer on Fatigue of Mechanically Fastened Metallic Joints

    Lee, EU
    Materials engineer, Naval Air Development Center, Warminster, PA

    Pages: 23    Published: Jan 1986


    Abstract

    Mechanically fastened joints are highly susceptible to fatigue cracking especially when varying loads are applied. The fatigue cracking is influenced by load transfer through fasteners.

    Tests were conducted using zero, low, medium, and high load transfer specimens of 7475-T7351 aluminum. The fatigue crack initiation and growth and the final fracture behaviors were investigated. The fatigue crack initiation life, Ni, and the total fatigue life, Nf, are reduced by increasing stress range, Δσ, and load transfer level, L. The relationship is defined by the equations of the form logN=CBΔσDLH where C, B, D, and H are constants. The fatigue crack growth rate, da/dN, is related to the stress intensity factor range, ΔK, by the equation dadN=(2.36×107)·(ΔK)2.89mm×cycle The crack initiation portion of the total fatigue life, Ni/Nf, is greater with lower stress range, Δσ, and longer total fatigue life, , is greater with lower stress range, Δσ, and longer total fatigue life, Nf, and it is reduced by load transfer.

    Keywords:

    mechanically fastened joints, load transfer, constant amplitude loading, fatigue, stress ratio, stress range, frequency, crack initiation, crack growth, fatigue life


    Paper ID: STP29057S

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP29057S


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