Crack closure and residual stress effects in fatigue of a particle-reinforced metal matrix composite

D.M. Knowles, T.J. Downes, J.E. King

    Research output: Contribution to journalArticlepeer-review


    A study of the influence of macroscopic quenching stresses on long fatigue crack growth in an aluminium alloy-SiC composite has been made. Direct comparison between quenched plate, where high residual stresses are present, and quenched and stretched plate, where they have been eliminated, has highlighted their rôle in crack closure. Despite similar strength levels and identical crack growth mechanisms, the stretched composite displays faster crack growth rates over the complete range of ΔK, measured at R = 0.1, with threshold being displaced to a lower nominal ΔK value. Closure levels are dependent upon crack length, but are greater in the unstretched composite, due to the effect of surface compressive stresses acting to close the crack tip. These result in lower values of ΔKeff in the unstretched material, explaining the slower crack growth rates. Effective ΔKth values are measured at 1.7 MPa√m, confirmed by constant Kmax testing. In the absence of residual stress, closure levels of approximately 2.5 MPa√m are measured and this is attributed to a roughness mechanism.
    Original languageEnglish
    Pages (from-to)1189-1196
    Number of pages8
    JournalActa Metallurgica et Materialia
    Issue number4
    Publication statusPublished - Apr 1993


    • aluminum alloys
    • metal bars billets
    • crack propagation
    • fatigue of materials
    • plate metal
    • quenching
    • residual stresses
    • aluminum alloy silicon carbide composite silicon carbide
    • crack closure
    • long fatigue crack growth
    • macroscopic quenching stresses
    • roughness mechanism
    • surface compressive stresses, Metallic matrix composites


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