STP1480

    Fatigue Strength in Presence of Inhomogeneities: Influence of Constraint

    Published: Jan 2007


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    Abstract

    The effect of defects on the entity of the fatigue limit is nowadays well known and is demonstrated to be equivalent to the nonpropagating condition of short cracks. The influence of constraint at the defect tip has been addressed in the present paper considering a mild steel whose mechanical behavior has been experimentally determined together with the propagation threshold values for long cracks. The activity has first dealt with the determination of the Kitagawa diagram by means of fatigue limit tests using specimens containing micro-notches with different shapes (drilled holes and narrow slits). Experimental results showed a significant influence of the defect shape on the fatigue limit and thresholds. In order to understand the reasons, defects have then been analyzed by elasto-plastic FEM analyses. Computational results have confirmed a significant difference in the global constraint factor at the crack tip between round and narrow defects.

    Keywords:

    fatigue, constraint factor, defect shape, fatigue thresholds


    Author Information:

    Beretta, Stefano
    Professor, Researcher, and Ph.D. Student, Politecnico di Milano, Milano,

    Carboni, Michele
    Professor, Researcher, and Ph.D. Student, Politecnico di Milano, Milano,

    Madia, Mauro
    Professor, Researcher, and Ph.D. Student, Politecnico di Milano, Milano,


    Paper ID: STP45509S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP45509S


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