STP948

    Fractographic Aspects of the Effect of Environment on the Fatigue Crack Propagation Mechanism in a High-Strength Aluminum Alloy

    Published: Jan 1987


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    Abstract

    Fatigue crack propagation tests were conducted in three different environments, air, vacuum, and high purity nitrogen (N2) [3 ppm water vapor (H2O) + 1 ppm oxygen (O2)], on a high-strength aluminum alloy, 2024-T351. From tests conducted at a load ratio of 0.5, a typical behavior in the N2 environment is brought into light. At moderate ΔK-values, the crack growth behavior in N2 is similar to that observed in vacuum. As ΔK decreases, the crack growth curve shifts towards the one obtained in air showing a progressive environmental effect occurring in the presence of traces of water vapor.

    The fractographic observations for these tests show that the environmental effect observed in the crack growth curves is accompanied by changes in the fracture surface morphology.

    The observed results are discussed considering an energy-based model and by taking into account a discontinuous crack growth mechanism at low growth rates.

    Keywords:

    fatigue crack propagation, specific energy, fractography, striations, coarse slip steps, discontinuous crack growth, crack growth model


    Author Information:

    Ranganathan, N
    Maître de conferences, E.N.S.M.A., Poitiers,

    Bouchet, B
    Ingenieur de recherche, E.N.S.M.A., Poitiers,

    Petit, J
    Directeur de recherche, E.N.S.M.A., Poitiers,


    Paper ID: STP25632S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP25632S


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