The current methods of fatigue life estimation do not model the interaction of stress with microstructural discontinuities. An experimental study of fatigue crack nucleation in 7075-T6 and 7079-T6 aluminum alloy sheet was performed to obtain more information on the role of discontinuities in the microstructure and to determine the relative contributions of each type of discontinuity. Some specimens were machined from recently manufactured material without any coating (cladding or anodizing). Some were fabricated from old clad-anodized material from an aircraft fuselage and old anodized material from a stock of unused wing panels. In the uncoated materials, large constituent particles and the surface roughness were found to be important factors in fatigue crack nucleation. In the coated materials, discontinuities related to the cladding and anodizing appeared to be the controlling factors in crack nucleation and particles did not play any role. The coated specimens showed a low scatter and a relatively low fatigue life. Multiple nucleation sites were observed in the coated materials. In the uncoated 7075-T6 materials in this study, large, iron-bearing, constituent particles were a factor in 25% of the failures, but marks due to material manufacture on the wide (LT) faces of the specimens appear to have been the predominant source of failure. In the coated 7075-T6511 and 7079-T6 specimens, all nucleation sites were located on a wide face, and the main controlling factor for crack nucleation appears to have been the coating: anodizing, shot-peening and anodizing, or cladding and anodizing. Particles played no role in fatigue crack nucleation in the coated specimens. The fatigue test data also indicated that the coatings were detrimental in fatigue. Another difference observed in the coated (clad and/or anodized) specimens was the presence of multiple nucleation sites on some of the fracture surfaces.


    Access

    Access via TIB

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Determination of fatigue related discontinuity state of 7000 series of aerospace aluminum alloys


    Additional title:

    Bestimmung des ermüdungsbezogenen Diskontinuitätszustandes der 7000er Reihe von Raumfahrt-Aluminiumlegierungen


    Contributors:

    Published in:

    Publication date :

    2007


    Size :

    13 Seiten, 11 Bilder, 2 Tabellen, 22 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




    Corrosion-Fatigue Crack Initiation in 7000-Series Aluminum Alloys

    Pao, P. S. / Feng, C. R. J. / Gill, S. J. et al. | British Library Conference Proceedings | 1999


    Modeling Time-Dependent Corrosion Fatigue Crack Propagation in 7000 Series Aluminum Alloys

    Mason, M. E. / Gangloff, R. P. / United States; Federal Aviation Administration et al. | British Library Conference Proceedings | 1994


    Determination of Fatigue-Related Features of the Initial Discontinuity State of Aluminum Alloy

    Merati, A. A. / International Committee on Aeronautical Fatigue | British Library Conference Proceedings | 2004


    Dynamic properties of 7000 - series aluminum alloys at large strain rates

    Jurczak, Wojciech / Kyzioł, Lesław | Online Contents | 2012


    Fatigue Crack Propagation in Aerospace Aluminum Alloys

    Gangloff, R.P. | Online Contents | 1994