This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Strain Hardening”.
1. Which property deteriorates on strain hardening?
a) Hardness
b) UTS
c) Ductility
d) Yield strength
View Answer
Explanation: Strain hardening improves metals’ hardness. It also improves UTS and yield strength. Ductility on other hand deteriorates due to dislocation forest.
2. Which term is different from other options?
a) Strain hardening
b) Dislocation hardening
c) Cold working
d) Work hardening
View Answer
Explanation: Strain hardening is also known as work hardening or cold working. Cold deformation causes an increase in dislocation density. Plastic deformation causes hardening of metal.
3. Toughness of metal with strain hardening ___________
a) Increases
b) Decreases
c) Remains constant
d) First increases and then decreases
View Answer
Explanation: Toughness in general decreases on strain hardening. Toughness is a combination of UTS and ductility. Ductility decreases on strain hardening so does toughness.
4. In highly ductile materials, toughness ___________ with the strain hardening.
a) Increases
b) Decreases
c) Remains constant
d) First increases and then decreases
View Answer
Explanation: In highly ductile materials, toughness first increases and then decreases with work hardening. This is because toughness is a combination of UTS and ductility both. Hence good property combination can be obtained by work hardening.
5. Which property decreases on strain hardening?
a) Elastic modulus
b) Percent elongation
c) Yield strength
d) Hardness
View Answer
Explanation: Elastic modulus of metal increases slightly on strain hardening. Yield strength and hardness also improve. But it adversely decreases the percent elongation.
6. Electrical resistivity of an alloy ____________ with increasing degree of cold working.
a) Increases
b) Decreases
c) Remains constant
d) First increases then decrease
View Answer
Explanation: Electrical resistivity of an alloy increases with increasing degree of cold working. It is due to an increase in scattering of electrons with dislocations.
7. Coercive force of permanent magnets __________ with increase in cold working.
a) Increases
b) Decreases
c) Remains constant
d) First increases and then decreases
View Answer
Explanation: Cold working improves the magnetic properties of materials. It increases coercive forces of permanent magnets. Hence cold working is important in ferromagnetic materials.
8. Strain hardening ____________
a) Increases density
b) Decreases coefficient of thermal expansion
c) Increases internal energy
d) Increases corrosion resistance
View Answer
Explanation: Strain hardening increases internal energy of material. Hence corrosion resistance decreases. It decreases density and increases coefficient of thermal expansion to a little extent.
9. Which material can be deep drawn?
a) Rapid work hardening
b) Slow work hardening
c) Low workable
d) Slow work hardening alloys with low workability
View Answer
Explanation: Materials with rapid work hardening can be deep drawn. Deep drowning requires high rates of work hardening. It also requires good workability.
10. 2 No. or half hard represents __________ of cold reduction.
a) 11%
b) 20%
c) 40%
d) 60%
View Answer
Explanation: 2 No. or half hard represents 20% cold reduction. 1No. or one quarter hard represents 11% reduction of original thickness. 4 No. or full hard represents 60% of cold reduction.
11. Polycrystalline metal work harden more rapid than a single crystal.
a) True
b) False
View Answer
Explanation: Work hardening is seen in both single and polycrystalline materials. But rate at which these work harden differ. Single crystal work hardens slower than polycrystalline metal.
12. Strain hardening is caused by glissile dislocations.
a) True
b) False
View Answer
Explanation: Strain hardening is a result of an increase in the density of dislocations. These dislocations are generally sessile. These are dislocations of lower mobility.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
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