STP857

    Effect of Low Temperature on Apparent Fatigue Threshold Stress Intensity Factors

    Published: Jan 1985


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    Abstract

    Near-threshold fatigue crack growth in high-strength low-alloy (HSLA) steel, Fe, and Fe-Si alloys was found to depend on test temperature from room temperature down to 123 K. Near-threshold crack growth rates were lowered and threshold stress intensity factors increased with decreasing temperature. A “prominent” closure was observed for all test temperatures and materials and was further confirmed by the examination of fracture surfaces. The magnitude of closure increased with decreasing temperature, suggesting a dependence on yield strength and fracture morphology. The effects of R ratio were found to be closure-related for the same fracture processes. However, a change in the fracture process, (e.g., to cyclic cleavage) may lead to a ΔKth(eff) dependence on load ratio even at very high R values. Hence mean stress may affect threshold independently of any closure-related phenomena. A reasonable correlation was obtained with a theoretical model for closure that could account for both geometrical and reversed plasticity phenomena.

    Keywords:

    closure, fatigue crack propagation, fatigue thresholds, fractography, HSLA steel, iron alloys, low temperatures, load ratio


    Author Information:

    Esaklul, KA
    professorassistant professorpostdoctoral associate, University of MinnesotaFaculty of Engineering, Al-Fateh UniversityUniversity of California, MinneapolisTripoliBerkeley, MNCA

    Yu, W
    professorassistant professorpostdoctoral associate, University of MinnesotaFaculty of Engineering, Al-Fateh UniversityUniversity of California, MinneapolisTripoliBerkeley, MNCA

    Gerberich, WW
    professorassistant professorpostdoctoral associate, University of MinnesotaFaculty of Engineering, Al-Fateh UniversityUniversity of California, MinneapolisTripoliBerkeley, MNCA


    Paper ID: STP32747S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP32747S


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