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    Analysis of Nonproportional Multiaxial Fatigue Test Data of Various Aluminum Alloys Using a New Damage Parameter

    Published: 01 April 2017

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    This paper presents a detailed investigation into nonproportional loading-induced multi–axial fatigue damage in a series of aluminum alloys using a recently developed moment of load path (MLP) model that contains a material sensitivity parameter. A generalized procedure is presented for determining material sensitivity to nonproportional load path and is demonstrated for characterizing multi–axial fatigue damage in these aluminum alloys under nonproportional loading conditions. Major findings are: (a) All of the alloys studied in this paper show a lesser degree of sensitivity to nonproportional loading when comparing structural steels recently reported by the same authors with material sensitivity parameter (α defined with respect to stress plane or αɛ as to strain plane) ranging from 0.35 to 0.5, which is much smaller than that of structural steels that were found to be around unity (i.e., α ≈ αɛ ≈ 1; (b) within the same aluminum alloy type, it is found that material sensitivity parameter (α) calculated on stress plane using stress–life test data is close to the values calculated on strain plane using strain–life data (i.e., αɛ); and (c) with the material sensitivity parameter (α or αɛ) being determined, MLP–based equivalent stress (defined on σ − √βτ plane) or equivalent strain (on ɛ − √βɛγ) are shown to be effective in correlating a large amount of multi–axial fatigue test data subjected to a varying degree of load–path nonproportionality.


    multi-axial fatigue, aluminum alloys, nonproportional loading, fatigue damage modeling, damage parameter, moment of load path, material sensitivity

    Author Information:

    Mei, Jifa
    University of Michigan, Dept. of Naval Architecture and Marine Engineering, Ann Arbor, MI

    Dong, Pingsha
    University of Michigan, Dept. of Naval Architecture and Marine Engineering, Ann Arbor, MI

    Committee/Subcommittee: E08.03

    DOI: 10.1520/STP159820160079