This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Ductile-Brittle Transition Behaviour”.
1. On increasing temperature, a material tends to loose its ability to resists plastic deformation is due to decrease in _________________
a) Tensile stress
b) Yield stress
c) Compressive stress
d) Shear stress
View Answer
Explanation: On the increasing temperature, a material tends to lose its ability to resists plastic deformation is due to a decrease in yield stress. Yield stress decreased due to free movement of dislocations at high temperatures.
2. With increasing ___________ material’s amount of deformation which can be achieved decreases.
a) Temperature
b) Slip systems
c) Strain rate
d) Vacancies
View Answer
Explanation: With the increase in strain rate, the ability of the material to undergo plastic deformation decreases. While temperature increases the percentage of deformation.
3. With increase in __________ plastic deformation amount also increases.
a) Triaxiality
b) Notching
c) Temperature
d) Rate of loading
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Explanation: WWith the increase in temperature the amount of plastic deformation increases and it is due to sufficient activation energy for the dislocation to jump and to cross obstacles.
4. What causes a brittle fracture?
a) Notch
b) Vacancy
c) Dislocation
d) Holes
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Explanation: Notch generates the condition of triaxiality. It causes the material to show brittle fracture. Vacancies help to move dislocation and hence improve ductility.
5. What term is used for the energy absorbed by the material without undergoing failure under dynamic loading?
a) Impact toughness
b) Static toughness
c) Compressive strength
d) Bend strength
View Answer
Explanation: The energy absorbed by the material without undergoing failure under dynamic loading is known as static toughness. It is related to static loading.
6. What is the comparison for static and dynamic toughness?
a) Static toughness higher
b) Both equal
c) Dynamic toughness higher
d) Can’t say
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Explanation: On dynamic loading, the material undergoes less deformation. It leads to less energy absorbed or toughness.
7. Which material is sensitive to temperature drop?
a) Cu
b) Al
c) Ni
d) Ferritic steel
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Explanation: Ferritic steel has a BCC structure. It is more sensitive to temperature. Cu, Al, and Ni are FCC structures with less sensitivity.
8. What is the reason for Ductile-Brittle transition in BCC materials?
a) Cracks
b) Compressive stresses
c) Peierls-Nabarro stress
d) Vacancies
View Answer
Explanation: Peierls-Nabarro stress is larger for BCC metals than FCC metals. It is due to non-close packed planes. It causes Ductile-Brittle transition.
9. What is the transition temperature range for ceramics?
a) 0.1 – 0.2 Tm
b) 0.3 – 0.5 Tm
c) 0.5 – 0.7 Tm
d) 0.7 – 0.9 Tm
View Answer
Explanation: For metals, the transition range is 0.1-0.2 Tm. While it is higher for ceramics, it is 0.5 to 0.7 Tm, where Tm is absolute melting temperature.
10. Sharper the notch in a specimen, the higher will be the _________ and low the _________
a) Crystallization temperature, Impact toughness.
b) Transition temperature, impact toughness
c) Transition temperature, Fracture stress
d) Crystallization temperature, fracture stress
View Answer
Explanation: Sharper the notch in specimen, the higher will be transition temperature. It causes a decrease in the impact toughness.
11. Transition range is 0.5 – 0.7 Tm for metals.
a) True
b) False
View Answer
Explanation: Transition range for metals is lower. It is 0.1 – 0.2 Tm. For ceramics, it is 0.5 – 0.7 Tm.
12. Transition temperature is defined at 50% fibrous fracture.
a) True
b) False
View Answer
Explanation: Transition temperature is defined at 50% fibrous fracture generally. This appearance plays an important role.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
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