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9.13: Questions

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  • Quick questions

    You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

    The Lennard-Jones potential best describes which of the following:

    a The energy required to break a typical metal
    b How flaws affect the energy of a lattice
    c The energy associated with stretching an atom


    Which of the following situations is required for fast fracture to occur?

    a The crack tip is sufficiently sharp
    b dG/dc is greater than dR/dc
    c The applied stress is near the ultimate tensile strength of the material
    d The strain energy release rate G is equal to the fracture energy R.


    In the wedging setup, which of the following will *not* influence the critical crack length?

    a The position of the wedge
    b The stiffness of the material
    c The thickness of the peeling layer
    d The surface energy of the material


    Which one of Irwin's modes of fracture best describes a car tyre skidding on a dry road?

    a Mode I
    b Mode II
    c Mode III


    What is the critical stress intensity factor equal to when no residual stresses are present?

    a Fracture toughness
    b Crack resistance
    c Ultimate tensile strength
    d Fracture energy


    What best describes the situation in wedging?

    a As the wedge position is varied, it is always energetically favourable for the crack to return to an equilibrium length
    b The fracture energy dominates at small crack lengths
    c If the crack becomes very long in comparison to the geometry of the setup, unstable fast fracture may occur


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