This set of Mechanical Behaviour test focuses on “Factors Affecting The Type of Fracture”.
1. Above equicohesive temperature, material fail in __________
a) Intergranular
b) Ductile fracture
c) Brittle fracture
d) Trans granular
View Answer
Explanation: Above equicohesive temperature, material fails in intergranular manner. It is because strength of grain boundary is lesser than grains.
2. What is more effective for brittle fracture?
a) Spheroids
b) Sharp crack tips
c) Blunted crack tips
d) Nodules
View Answer
Explanation: Sharp crack tips increases stress levels highly. While blunted crack tips are not that much effective. This causes the brittle fracture to occur.
3. What doesn’t favor a brittle fracture?
a) Tri-axial state of stress
b) A low temperature
c) High strain rate
d) Slow rate of loading
View Answer
Explanation: 3 factors favor brittle type of fracture. These are tri-axial state of stress, low temperature and high strain rate. Slow rate of loading results in ductile fracture.
4. In a Charpy test, high hammer velocity ensures ______
a) High strain rate
b) Local stresses
c) Ductility in fracture
d) Low stress concentration
View Answer
Explanation: High hammer velocity is ensured by high potential energy. It causes high strain rate. It gives brittle fracture.
5. A crack will propagate if the decrease in _____ is at least equal to the energy required to create the new crack surface.
a) Plastic energy
b) Elastic energy
c) Toughness
d) Resilience
View Answer
Explanation: For crack propagation, the decrease in elastic energy should be at least equal to energy increase. This energy increase is due to the formation of a new crack surface.
6. Automobile crankshaft is likely to undergo _____ fracture.
a) Ductile
b) Brittle
c) Intergranular
d) Fatigue
View Answer
Explanation: Automobile crankshaft undergoes alternating loading. It causes Fatigue failure. These occur after a considerable period of service.
7. Strain energy required in a ductile fracture is ____ and _____ in brittle.
a) Higher, higher
b) Higher, lower
c) Lower, higher
d) Lower, lower
View Answer
Explanation: In ductile fracture, higher strain energy is required. In brittle fracture lower strain energy is required. It is due to no plastic deformation.
8. How does fracture surface appear in brittle fracture?
a) Rough and dull
b) Smooth and bright
c) Cup and cone
d) Fibrous
View Answer
Explanation: Brittle fracture occurs without any plastic deformation. So surface looks bright and smooth. Cup and cone type is seen in ductile fracture.
9. Ductile fractured surface appears _____
a) Dull
b) Smooth
c) Bright
d) Flat
View Answer
Explanation: Ductile fracture appears rough and dull. It is because of displacement of planes. Brittle fracture on other hand appears smooth, bright and flat.
10. Stress during cracking _____ in ductile fracture and _____ in brittle.
a) Increases, increases
b) Increases, decreases
c) Increases, constant
d) Decreases, decreases
View Answer
Explanation: Stress during cracking increases in the ductile fracture. In brittle fracture, stress remains constant. It is due to no plastic deformation associated.
11. All metals fracture in a ductile manner.
a) True
b) False
View Answer
Explanation: Some HCP and BCC metals may fail in a brittle manner. It can occur in cold conditions. It is due to less number of slip planes present.
12. Little deformation takes place in brittle fracture.
a) True
b) False
View Answer
Explanation: In brittle materials, crack propagate at lower stresses. It results in no plastic deformation. So no warning is shown before failure.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
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