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| T/F: Since ductile materials absorb more energy before fracture, they are tougher than brittle materials. |
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| For a metal, given the stress-strain crve, one can determine the yield strain (σy) by drawing a parallel line to the elastic portion of the curve at the offset strain of: |
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| Which of the following is a measure of a material's ability to absorb energy prior to fracture? |
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Term
a) Briefly explain the meaning of resilience.
b) Give the modulus of resilience. |
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Definition
a) Measures the amount of energy absorbed by a stress during elastic deformation.
b) Ur = 1/2 σy Ey |
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| By using standardized impact testing measurements (Chary or Izod) one can measure the following: |
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T/F:
HCP crystalline structures has a larger number of slip systems than FCC structure. |
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Term
| According to the Hall-Petch equation and the general principles of the strengthening mechanisms for a given material the yield strength, σy, has the folling dependence on the grain size, d: |
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Definition
| σy is proportional to 1/√d |
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Term
| Briefly describe the strain hardening (or cold working) methodology. |
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Definition
| This is one of the strengthening mechanisms. Creating more dislocations in the metal will cause the substance to be harder. |
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Term
| Briefly describe the method you would use to eliminate the effects of strain hardening. |
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Definition
| This method is annealing heat treatment. |
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Term
T/F:
In a material under external loading considering two elliptical cracks of the same length the one having the largest radius of curvature experiences the largest stress at the crack tip. |
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Definition
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Term
| In the presence of an internal elliptical crack of half-length α and having the radius of curvature at the tip ρ, the stress concentration factor Kt is equal to: |
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Term
| When a crack is present, the fracture toughness of a material is indicative of its resistance to: |
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T/F:
Fracture toughness is a property that measures a material's resistance to elastic deformation. |
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Definition
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T/F:
Fatigue is a form of failure that occurs in structures subjected to cycling loading. Moreover, the fatigue failure occurs typically at stress levels larger than the yield stress for static loading. |
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Definition
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| For a ferrous alloy which of the following quantity is a measure of the stress level below which fatigue failure will not occur regardless of the number of cycles? |
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| List any three effective methods used to increase fatigue performance of a specimen. |
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Definition
a) shot peening
b) surface treatments (case hardening / carburizing nitrating)
c) imposing compressive stresses |
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Term
| Which of the three typical regions of a creep curve is characterized by a constant creep rate? |
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Definition
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| In the rectangle below give an approximate sketch of the strain versus time for a typical creep deformation process. Identify and indicate the regions characterizing the three typical creep regimes. |
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| In the rectangle below give an approximate sketch of the Cu-Ni isomorphous phase diagram. Indicate the quantities that are plotted along the horizontal and vertical axis. Indicate the melting temperatures for the pure elements and label the three distinct phase regions. How are the two phase-boundary line separators called? |
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| If you are given the Cu-Ni phase diagram and you know that for a given alloy the composition-temperature point is located in the two-phase region what is the rule used to determine the fractions of the two phases present? |
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