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5 Written questions

5 Matching questions

  1. Why is the ultimate tensile strength sometimes less than the maximum stress?
  2. (T/F) Stiffness of a dental prosthesis can increase by increasing its thickness.
  3. A value of 0.3 for Poisson's ratio is typical. Thus, the shear modulus is usually about ___% of the elastic modulus.
  4. Poisson's ratio
  5. which tooth structure has the hgiher <b>propotional limit</b> and <b>modulus of elasticity</b>?

    a. enamel
    b. dentin
  1. a the ratio of horizontal extension to vertical compression.

    Most engineering materials have values of approximately <b>0.3</b>
  2. b 38%
  3. c True

    however, the <b>elastic modulus</b> is always a constant. never changes! it describes material's <b>relative</b> stiffness.
  4. d
    a. enamel
  5. e Because of the reduction in area, the force required to increase deformation actually decreases.

5 Multiple choice questions

  1. The relative amount of elastic energy per unit volume released on unloading of a test specimen.
  2. b. parallel

    brackets for braces is a good example
  3. resilience

    the term resilience is associated with 'springiness'
  4. Maximum shear stress at the point of fracture of a test specimen.

  5. maximum elastic stress (proportional limit)

5 True/False questions

  1. Compressive strengthRatio of compressive force to cross-sectional area prependicular to the axis of applied force.

          

  2. in most cases fracture occurs because of the _____ stress component.

    a. compressive
    b. tensile
    c. shear
    b. tensile

          

  3. Strength depends on what factors: (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

          

  4. Why do prostheses sometimes fail under a very small force, even though the strength of the prosthetic material is relatively high?flexible

    The <b>maximum flexibility</b> is defined as the flexural strain that occurs when the material is stressed to its proportional limit.

          

  5. a different property, __________, is used in such cases when the proportional limit cannot be determined with sufficient accuracy.
    yield strength

    is a property that represents the stress value at which a small amount (0.1% or 0.2%) of plastic strain <b>has occurred</b>.

    Does not exist for very brittle materials

          

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