STP770: The Concept of Uniform Scatter Bands for Analyzing S-N Curves of Unnotched and Notched Specimens in Structural Steel

    Haibach, E
    Fraunhofer-Institut für Betriebsfestigkeit, Darmstadt,

    Matschke, C
    Fraunhofer-Institut für Betriebsfestigkeit, Darmstadt,

    Pages: 23    Published: Jan 1982


    Abstract

    From an extensive test program, 53 S-N curves, established for alternating, zero-tension, or fluctuating tension constant amplitude loading conditions, are obtained for unnotched and three types of centrally notched flat specimens of structural steel Ck 45 (SAE 1045) and 42 CrMo 4 (SAE 4140). These S-N curves are intended to improve existing fatigue design data for application of the two steels tested in cases of finite life design.

    The comparative evaluation of the test series reveals the possibility of describing the test results in log S-logN diagrams in terms of uniform scatter bands when distinguishing between the unnotched specimens, the notched specimens in the annealed condition, and the notched specimens in the quenched and tempered condition. These experimental findings are compared with an analytical analysis based on the local stress-strain approach using Neuber's rule. This analysis explains that the derived concept of uniform scatter bands is in accordance with our present understanding of the fatigue behavior of notched elements. Moreover, it allows the agreement of the analytical model and the actual material behavior to be critically examined. In conclusion the paper outlines the link between the nominal stress concept and the local stress-strain approach for deriving engineering fatigue design data.

    Keywords:

    S-N, curve, steel Ck 45 (SAE 1045), steel 42 CrMo 4 (SAE 4140), stress ratio, stress concentration factor, uniform scatter bands, slope, cut-off point, local stress-strain approach, Neuber's rule, design data


    Paper ID: STP32445S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP32445S


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