STP1461

    Effect of Periodic Overloads on Threshold Fatigue Crack Growth in Al-Alloys

    Published: Jan 2005


      Format Pages Price  
    PDF Version (468K) 16 $25   ADD TO CART
    Complete Source PDF (15M) 16 $139   ADD TO CART


    Abstract

    Experiments were performed on 10 mm thick C(T) specimens cut from Al-alloys to assess fatigue crack growth behavior under periodic overloads by comparison to constant amplitude loading. The tests were performed at a sufficiently high stress ratio to avoid crack closure, whose absence was confirmed from Load-COD response. ΔKth values were determined under these loadings in air, salt water, and vacuum. Even though closure was absent, ΔKth shows a systematic dependence on overload plastic zone ratio. Similar results were obtained in both air and salt water. In vacuum however, near threshold crack growth is accelerated by comparison to no-overload conditions, while higher growth rates see a reversal in this trend. These results appear to support the possibility that residual stress moderates cracktip surface chemistry in near-threshold fatigue, an effect that ceases in vacuum.

    Keywords:

    crack growth mechanisms, thresholds, residual stress effect, crack closure, periodic overloads, environmental action


    Author Information:

    Sunder, R
    BiSS Research, Bangalore,


    Paper ID: STP11517S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP11517S


    CrossRef ASTM International is a member of CrossRef.