Multi-Scale Approach to the Fatigue Crack Propagation in High-Strength Pearlitic Steel Wires

    Volume 5, Issue 6 (June 2008)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 30 June 2008

    Page Count: 15


    Toribio, J.
    Department of Materials Engineering, University of Salamanca, E. P. S., Campus Viriato, Zamora,

    González, B.
    Department of Materials Engineering, University of Salamanca, E. P. S., Campus Viriato, Zamora,

    Matos, J. C.
    Department of Materials Engineering, University of Salamanca, E. P. S., Campus Viriato, Zamora,

    Ayaso, F. J.
    Department of Materials Engineering, University of Salamanca, E. P. S., Campus Viriato, Zamora,

    (Received 13 November 2007; accepted 14 May 2008)

    Abstract

    This paper deals with the influence of the manufacturing process on the fatigue behavior of pearlitic steels with different degrees of cold drawing. The fatigue crack growth rate (da/dN) is related to the stress intensity range (ΔK) by means a compliance method to evaluate the crack depth a in the samples at any instant during the tests. The analysis is focused on the Region II (Paris) of the fatigue behavior in which da/dN=C(ΔK)m, measuring the constants (C and m) for the different degrees of drawing. From the engineering point of view, the manufacturing process by cold drawing improves the fatigue behavior of the steels, since the fatigue crack growth rate decreases as the strain hardening level in the material increases. In particular, the coefficient m (slope of the Paris Law) remains almost constant and independent of the drawing degree, whereas the constant C decreases as the drawing degree rises. The paper focuses on the relationship between the pearlitic microstructure of the steels (progressively oriented as a consequence of the manufacturing process by cold drawing) and the macroscopic fatigue behavior. To this end, a detailed metallographic analysis was performed on the fatigue crack propagation path after cutting and polishing on a plane perpendicular to the crack front. It is seen that the fatigue crack growth path presents certain roughness at the microscopic level, such a roughness being related to the pearlitic colony boundaries more than to the ferrite/cementite lamellae interfaces.


    Paper ID: JAI101564

    DOI: 10.1520/JAI101564

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    Author
    Title Multi-Scale Approach to the Fatigue Crack Propagation in High-Strength Pearlitic Steel Wires
    Symposium Seventh International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics (36th ASTM National Symposium on Fatigue and Fracture Mechanics), 2007-11-16
    Committee E08