Apparent Fracture Toughness Versus Micro-Scale Fracture Toughness of Interfaces—The Challenge of Critical Values

    (Received 7 October 2013; accepted 3 January 2014)

    Published Online: 2014

    CODEN: MPCOAD

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    Abstract

    This study aims to shed light on the conflict between macroscopic fracture toughness and small-scale measures of interface strength when the interface is simulated with an increasing resolution. In the design of practical structures, crack initiation is the critical, limiting phase of material behavior and needs to be defined by lucid means. In this study, we model an example structure, namely a fracture test specimen, including a bi-material interface having micro-roughness and thermal residual stresses. The initiation of secondary cracks, which is one of the microscopic mechanisms leading to crack coalescence, is studied. The work focuses on the effects of the bi-material's Young's modulus, residual stresses, and flaws. The simulation of crack propagation shows that the overall crack tip loading mode mixity distribution is not essentially affected when the Young's modulus of the bi-material's coating is doubled. The analysis of the secondary crack initiation due to interfacial flaws in turn showed that increasing the Young's modulus of either the bi-materials substrate or coating resulted in immediate interface collapse via an elongated ‘damage region’ along the interface.


    Author Information:

    Kanerva, M.
    Department of Applied Mechanics, Aalto Univ., Aalto,

    Jokinen, J.
    Department of Applied Mechanics, Aalto Univ., Aalto,

    Sarlin, E.
    Department of Materials Science, Tampere Univ. of Technology, Tampere,

    Saarela, O.
    Department of Applied Mechanics, Aalto Univ., Aalto,


    Stock #: MPC20130068

    ISSN: 2165-3992

    DOI: 10.1520/MPC20130068

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    Author
    Title Apparent Fracture Toughness Versus Micro-Scale Fracture Toughness of Interfaces—The Challenge of Critical Values
    Symposium , 0000-00-00
    Committee E08