STP1524

    Initiation Behavior of Crack Originated from Non-Metallic Inclusion in Rolling Contact Fatigue

    Published: Jan 2010


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    Abstract

    Recently, it has been generally accepted that flaking life is dependent on the size of non-metallic inclusion under proper condition in bearing use. Statistics of extreme values to predict the maximum non-metallic inclusion size and ultrasonic test to assess large non-metallic inclusions in a large volume are widely used as practical methods for the evaluation of bearing steel cleanliness. Murakami's formula is well known, which describes the relationship between non-metallic inclusion size and fatigue strength. However, the formula cannot be directly applied to rolling contact fatigue because of the difference in applied stress mode. While the equation was invented to predict the fatigue limit in principal stress mode, rolling contact fatigue is mainly caused by shear stress. It is expected that the condition of bearing use will be more critical due to the downsizing tendency in various industrial or automotive machine units. Thus the research on the flaking mechanism becomes more important from the viewpoint of global ecology because that is beneficial to the improvement in bearing life and methods for cleanliness evaluation. Due to the difficulty in experimental observation, however, the details of the flaking mechanism in rolling contact fatigue caused by non-metallic inclusion has not yet been clarified. Focusing on the relationship between non-metallic inclusion and initiation of the crack, the flaking mechanism is proposed in this paper.

    Keywords:

    bearing steel, rolling contact fatigue life, crack initiation, crack propagation, non-metallic inclusions, oxides, hot isostatic pressing


    Author Information:

    Tsunekage, Norimasa
    Senior Researcher of Engineering Steel Group, Sanyo Special Steel Co., Ltd., Himeji,

    Hashimoto, Kazuya
    Senior Researcher of Engineering Steel Group, Sanyo Special Steel Co., Ltd., Himeji,

    Fujimatsu, Takeshi
    Senior Researcher of Engineering Steel Group, Sanyo Special Steel Co., Ltd., Himeji,

    Hiraoka, Kazuhiko
    Head of Engineering Steel Group, Sanyo Special Steel Co., Ltd., Himeji,


    Paper ID: STP49125S

    Committee/Subcommittee: A01.06

    DOI: 10.1520/STP49125S


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