STP1184

    Influence of Crack Closure and Stress Ratio on Near-Threshold Fatigue Crack Growth Behavior in Ti-1100

    Published: Jan 1994


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    Abstract

    In the present study, the fatigue crack growth behavior of a near-α, β-processed titanium alloy, Ti-1100, was investigated with the objective of assessing the influence of crack closure and stress ratio on fatigue threshold. Measurement of the crack-opening load in single-edge tension [SE(T)] specimens was made by near-tip strain gage and DCPD methods. Fatigue threshold stress intensity ranges, ΔKth, determined under constant stress ratio and constant maximum stress intensity, variable stress ratio conditions indicate almost identical values for R above 0.5. It is postulated that while crack closure in the wake of the crack tip is responsible for the no-growth condition in the former case, lack of sufficient damage accumulation at the crack tip as a consequence of the formation of an insignificant reversed plastic zone and large planar slip band formations surrounding the crack tip appears to be responsible for no growth in the latter case. The use of an effective stress intensity based on closure data consolidates most of the threshold data, indicating the independence of the fatigue crack growth data to mean stress or R.

    Keywords:

    crack closure, stress ratio, threshold stress intensity range, effective stress intensity, damage accumulation, near-threshold crack growth behavior


    Author Information:

    Parida, BK
    Senior research associatesenior scientist, National Research CouncilMaterials Directorate, WL/MLLN, Wright-Patterson Air Force Base, OH

    Nicholas, T
    Senior research associatesenior scientist, National Research CouncilMaterials Directorate, WL/MLLN, Wright-Patterson Air Force Base, OH


    Paper ID: STP18119S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP18119S


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