STP833: Effects of Specimen Configuration and Frequency on Fatigue Crack Propagation in Nylon 66

    Lang, RW
    Research Assistant, Materials Research Center, Lehigh University, Bethlehem, Pa.

    Hahn, MT
    Research Assistant, Materials Research Center, Lehigh University, Bethlehem, Pa.

    Hertzberg, RW
    New Jersey Zinc Professor and Professor of Chemistry, Materials Research Center, Lehigh University, Bethlehem, Pa.

    Manson, JA
    New Jersey Zinc Professor and Professor of Chemistry, Materials Research Center, Lehigh University, Bethlehem, Pa.

    Pages: 18    Published: Jan 1984


    Abstract

    Fatigue crack propagation (FCP) rates were measured in nylon 66 as a function of test frequency using center-cracked-tension (CCT) and wedge-open loading (WOL) specimens. In order to enhance any effects of stress- and frequency-induced changes in the dynamic modulus and to maximize the capability for hysteretic heat generation, the nylon was equilibrated to a water content of 4.7% by weight. For this water content the glass transition region of the material occurs at around the fatigue test temperature. FCP rates determined using CCT specimens were found to be consistently higher at all frequencies than those using WOL specimens. In addition, hysteretic heat-up measured at the crack tip and across the whole unbroken ligament was higher in the CCT specimens. These results are related to the differences in the far field stress profiles and their effect on the relative specimen stiffness and on the heat generation capability. Effects of test frequency are discussed in terms of changes in strain rate and the beneficial and detrimental effects of local crack tip and general specimen heating.

    Keywords:

    fatigue crack propagation, fracture mechanics, engineering plastics, nylon 66, specimen configuration, frequency, hysteretic heating, nonlinear viscoelasticity


    Paper ID: STP32559S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP32559S


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