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5 Written Questions

5 Matching Questions

  1. fatigue failure
  2. As the interatomic spacing increases, the internal energy increases. As long as the stress is <b>not greater than the proportional limit</b>, this <u>energy</u> is known as__________.
  3. Yield strength
  4. Strain
  5. A _______ stress is caused by a load that tends to stretch or elongate a body.

    a. compressive
    b. tensile
    c. shear
  1. a b. tensile
  2. b
    Repeated stresses resulting in fractures. the fracture due to fatigue occurs at stress levels well below tensile strength.
  3. c resilience

    the term resilience is associated with 'springiness'
  4. d
    Change in length per unit initial length.

    Units are in %
  5. e
    • The <b>stress</b> at which a test specimen exhibits a specific amount of plastic strain (0.2%)

    • The YS at 0.2% strain offset from the origin is 1536 MPa in this case.

5 Multiple Choice Questions

  1. Ultimate strength
  2. Stress and/or strain
  3. Ability of a material to absorb elastic energy and to deform plastically before fracturing; measured as the total area under a plot of tensile stress vs. tensile strain.
  4. 1. <b>strain rate</b>
    2. the shape of the test speciment
    3. the surface finish (control flaws)
    4. the environment in which material is tested
  5. Relative stiffness of a material; ratio of elastic stress to elastic strain

5 True/False Questions

  1. Materials with a high elastic modulus have:

    a. high strength values.
    b. low strength values.

    b. dentin

    dentin → 50 MPa
    enamel → 10 MPa

          

  2. Two important aspects of microscopic flaws in brittle materials:1. tensile stress
    2. shear stress
    3. compressive stress

          

  3. Units of Modulus of elasticity
    Maximum stress at which stress is proportional to strain and above which plastic deformation occurs.

    in this case: PL= 1020 MPa

          

  4. Tensile strength for:

    a. Dental porcelain
    b. Amalgam
    c. Resin-based composite
    d. Poly
    e. Alumnia ceramic
    a. Dental porcelain → 50-100 MPa
    b. Amalgam → 27-55 MPa
    c. Resin-based composite → 30-90 MPa
    d. Poly → 60 MPa
    e. Alumnia ceramic → 120 MPa

          

  5. Stress concentrationMaximum amount of plastic strain a tensile test specimen can sustain before it fractures (See Ductility).

          

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