STP791: A Superposition Model for Corrosion-Fatigue Crack Propagation in Aluminum Alloys

    Kim, YH
    Senior research scientist and engineering specialist senior, Materials Research Laboratory, General Dynamics, Fort Worth, Tex.

    Manning, SD
    Senior research scientist and engineering specialist senior, Materials Research Laboratory, General Dynamics, Fort Worth, Tex.

    Pages: 17    Published: Jan 1983


    Abstract

    The mechanism for fatigue crack growth in aluminum alloys under a chemically aggressive environment is discussed, based on the current understanding of hydrogen embrittlement phenomena. This mechanism is discussed quantitatively in terms of the three-term superposition model proposed by Wei et al. A diffusion-controlled model, characterizing the cycle-dependent interaction of fatigue loading and environmental attack, is developed, based on the assumption that crack growth enhancement results from microvoid nucleation due to hydrogen accumulation at inhomogencities ahead of a crack tip. This model is evaluated with limited data on Aluminum 7075-T6. The model developed in this paper accounts for the significant parameters affecting corrosion-fatigue crack growth enhancement. Integration of this model into the superposition scheme is discussed, including the application to predicting crack growth behavior in a corrosive environment for spectrum loading.

    Keywords:

    corrosion fatigue, crack growth enhancement, crack propagation (growth), environment, fracture mechanics, hydrogen embrittlement, Paris' region, retardation, spectrum loading, superposition model, sustained load crack growth


    Paper ID: STP37087S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP37087S


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