STP1292

    Fatigue Crack Propagation in IN-718 Material under Biaxial Stress Bending

    Published: Jan 1996


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    Abstract

    The effect of biaxial stress cycling on the crack growth process in IN-718 plate specimens was investigated using a semielliptical surface flaw as a crack starter. The method of anticlastic bending was used to generate the biaxial stress field. This bending method generates two bending stresses: a tensile stress normal to the crack surface and a compressive stress transverse to the tensile stress at the tip of the crack. In a biaxial stress field, the linear elastic fracture mechanics (LEFM) theory predicts that the stress parallel to the crack direction has no effect on crack growth rate. However, in the past two decades, experimental studies have shown that a stress parallel (transverse) to the crack tip influences crack growth rate. In this investigation, the effect of biaxial stress ratio (β = − σ21) of − 1 on fatigue crack growth is presented. At a constant cyclic load, a crack growth transition from Mode I to Mode II was observed to take place when ΔK reached the value of 17.5 ksi √in. (19.2 MPa √m). Also, an acceleration in the fatigue crack growth rate was observed due to the compressive transverse stress.

    Keywords:

    fatigue, crack growth, anticlastic bending, biaxial stress cycling


    Author Information:

    Zamrik, SY
    The Pennsylvania State University, University Park, PA

    Ryan, RE
    The Pennsylvania State University, University Park, PA


    Paper ID: STP16137S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP16137S


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