Influence of macroscopic residual stress fields on fatigue crack growth measurement in SiC particulate reinforced 8090 aluminium alloy

D.M. Knowles, J.E. King

    Research output: Contribution to journalArticle

    Abstract

    The effect of residual stresses, induced by cold water quenching, on the morphology of fatigue crack fronts has been investigated in a powder metallurgy 8090 aluminium alloy, with and without reinforcement in the form of 20 wt-%SiC particles. Residual stress measurements reveal that the surface compressive stresses developed in these materials are significantly greater than in conventional metallurgy ingot 8090, because surface yielding occurs on quenching. The yield stresses of the powder route materials are greater than those of ingot produced 8090 and hence greater surface stresses can be maintained. In fatigue, severe crack front bowing is observed in the powder formed materials as a result of the reduction of the R ratio (minimum load/maximum load) by the compressive residual stresses at the sides of the specimen, causing premature crack closure and hence reducing the local driving force for fatigue crack growth ΔKeff. This distortion of the crack fronts introduces large errors into measurements of crack growth rate and threshold values of ΔK.
    Original languageEnglish
    Pages (from-to)1015-1020
    Number of pages6
    JournalMaterials Science and Technology
    Volume7
    Issue number11
    DOIs
    Publication statusPublished - Nov 1991

    Fingerprint

    Fatigue crack propagation
    aluminum alloys
    particulates
    stress distribution
    residual stress
    Aluminum alloys
    Residual stresses
    cracks
    Ingots
    Compressive stress
    Powders
    Quenching
    Loads (forces)
    ingots
    Bending (forming)
    Crack closure
    Stress measurement
    Powder metallurgy
    Metallurgy
    Measurement errors

    Keywords

    • fatigue of materials
    • fracture mechanics
    • heat treatment quenching
    • powder metallurgy aluminum
    • silicon carbide mechanical properties
    • aluminum alloy 8090
    • fatigue crack growth
    • aluminum and alloys

    Cite this

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    abstract = "The effect of residual stresses, induced by cold water quenching, on the morphology of fatigue crack fronts has been investigated in a powder metallurgy 8090 aluminium alloy, with and without reinforcement in the form of 20 wt-{\%}SiC particles. Residual stress measurements reveal that the surface compressive stresses developed in these materials are significantly greater than in conventional metallurgy ingot 8090, because surface yielding occurs on quenching. The yield stresses of the powder route materials are greater than those of ingot produced 8090 and hence greater surface stresses can be maintained. In fatigue, severe crack front bowing is observed in the powder formed materials as a result of the reduction of the R ratio (minimum load/maximum load) by the compressive residual stresses at the sides of the specimen, causing premature crack closure and hence reducing the local driving force for fatigue crack growth ΔKeff. This distortion of the crack fronts introduces large errors into measurements of crack growth rate and threshold values of ΔK.",
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    Influence of macroscopic residual stress fields on fatigue crack growth measurement in SiC particulate reinforced 8090 aluminium alloy. / Knowles, D.M.; King, J.E.

    In: Materials Science and Technology, Vol. 7, No. 11, 11.1991, p. 1015-1020.

    Research output: Contribution to journalArticle

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    AU - Knowles, D.M.

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    AB - The effect of residual stresses, induced by cold water quenching, on the morphology of fatigue crack fronts has been investigated in a powder metallurgy 8090 aluminium alloy, with and without reinforcement in the form of 20 wt-%SiC particles. Residual stress measurements reveal that the surface compressive stresses developed in these materials are significantly greater than in conventional metallurgy ingot 8090, because surface yielding occurs on quenching. The yield stresses of the powder route materials are greater than those of ingot produced 8090 and hence greater surface stresses can be maintained. In fatigue, severe crack front bowing is observed in the powder formed materials as a result of the reduction of the R ratio (minimum load/maximum load) by the compressive residual stresses at the sides of the specimen, causing premature crack closure and hence reducing the local driving force for fatigue crack growth ΔKeff. This distortion of the crack fronts introduces large errors into measurements of crack growth rate and threshold values of ΔK.

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