# Mechanical Behaviour Questions and Answers – Ductile-Brittle Transition Behaviour

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This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Ductile-Brittle Transition Behaviour”.

1. On increasing temperature, a material tends to lose the capacity of deformation due to increased ___________
a) Tensile stress
b) Yield stress
c) Compressive stress
d) Shear stress

Explanation: With a decrease in temperature, a material tends to lose the ability to deform. It is because of a decrease in yield stress.

2. With increasing ___________ material’s amount of deformation which can be achieved decreases.
a) Temperature
b) Slip systems
c) Strain rate
d) Vacancies

Explanation: With an increase in strike rate, strain rate increases. The ability of a material to undergo plastic deformation decreases. While temperature has the quite opposite effect.

3. With increase in __________ plastic deformation amount also increases.
a) Triaxiality
b) Notching
c) Temperature

Explanation: With a decrease in temperature, plastic deformation amount decreases. It is because of active slip planes. Rate of loading has the opposite effect.

4. What causes a brittle fracture?
a) Notch
b) Vacancy
c) Dislocation
d) Holes

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

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

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

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

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

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

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

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