Crack initiation and propagation in an SAE 4320 steel gas carburized to a 1.0 mm case depth was examined in specimens subjected to bending fatigue. Cellulose acetate replicas of incrementally loaded specimens showed that small, intergranular cracks were initiated during static loading to stress levels just above the endurance limit. The intergranular cracks arrest and serve as initiation sites for semi-elliptical, transgranular fatigue crack propagation. The maximum depth of stable crack propagation was between 0.17 and 0.23 mm, a depth which corresponds to the maximum hardness of the carburized case. Three equations which provide approximations to the stress distribution in the fatigue specimens were used to calculate KIC for the carburized case with values of maximum applied stress and measured stable crack geometry. Although all three equations yielded values in good agreement with published values of KIC for high-carbon, hardened steels, the equation for a semi-elliptical, surface crack under a bending stress state was judged superior. Variations in KIC are discussed relative to crack initiation geometry, strain-induced austenite transformation, and residual stresses.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Bending Fatigue Crack Characterization and Fracture Toughness of Gas Carburized SAE 4320 Steel


    Additional title:

    Sae Technical Papers


    Contributors:

    Conference:

    International Congress & Exposition ; 1992



    Publication date :

    1992-02-01




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




    Bending fatigue crack characterization and fracture toughness of gas carburized SAE 4320 steel

    Hyde,R.S. / Cohen,R.E. / Matlock,D.K. et al. | Automotive engineering | 1992


    Bending Fatigue Performance of Carburized 4320 Steel

    Matlock, David K. / Krauss, George / Cohen, Rachael E. | SAE Technical Papers | 1993


    Bending fatigue performance of carburized 4320 steel

    Cohen,R.E. / Krauss,G. / Matlock,D.K. et al. | Automotive engineering | 1993



    Effects of Subzero Treatments on the Bending Fatigue Performance of Carburized SAE-4320 and SAE-9310 Steels

    Medlin, D. J. / Krauss, G. / Jung, Seung-Cheal | SAE Technical Papers | 1996