This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Ductile Fracture”.
1. Which of the following is not a stage of ductile fracture?
a) Nucleation of crack
b) Growth of crack
c) Coalescence of cracks
d) Development of tensile stresses
View Answer
Explanation: Ductile fracture has 3 stages. These are nucleation, growth and coalescence of cracks. It takes sufficient time so fracture can be detected.
2. Cracks can’t nucleate at ____________
a) Grain boundaries
b) Crystal
c) Interfaces
d) Inclusion brittle particles
View Answer
Explanation: Cracks generally nucleate at irregularities. These may be grain boundaries, interfaces or inclusions. These may be Fe3C particles in case of steel.
3. In aluminum copper system, which causes crack initiation?
a) Fe3C
b) CuAl2
c) Ti3Al
d) NiAl
View Answer
Explanation: CuAl2 particles in aluminum copper system causes crack nucleation. These provide an interface between matrix and particles. These cause tensile stresses.
4. What causes nucleation of crack in steel?
a) CuAl2
b) Ti3Al
c) Oxides
d) Fe3C
View Answer
Explanation: Fe3C particles are brittle. These generate tensile stresses in matrix. Which causes nucleation of crack.
5. What is nucleation sites in copper?
a) CuAl2
b) Fe3C
c) Oxide inclusions
d) NiAl
View Answer
Explanation: Oxide inclusions are major nucleation sites for crack. These provide the matrix with irregularity. It increases interfacial energy.
6. Titanium aluminum alloys generate cracks due to ___________ particles.
a) Ti3Al
b) Fe3N
c) CuAl2
d) Oxide inclusions
View Answer
Explanation: Ti3Al particles cause cracks in titanium aluminum alloys. These are known as intermetallic compounds. These have refractory properties.
7. On stressing a material, necking starts at a point of _______________
a) Plastic instability
b) Higher elastic modules
c) Higher regular arrangement
d) Higher stress
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Explanation: On stressing a material, necking starts at a point of instability. It occurs in ductile materials when uniaxial stress is applied.
8. _____________ occurs during tensile deformation.
a) Compressive stress
b) Strain hardening
c) Forging
d) Shear stress
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Explanation: Strain hardening occurs during tensile deformation. It is due to dislocation multiplication. Frank-Reed source is the reason for this work hardening.
9. What region is first encountered by the material on a tensile test?
a) Elastic
b) Yielding
c) Strain hardening
d) Necking
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Explanation: Elastic region is encountered by the material firstly. In this region deformation is temporary. Material attains its original shape after removal of the load.
10. What region is encountered after elastic deformation on a tensile test?
a) Strain hardening
b) Yielding
c) Necking
d) Fracture
View Answer
Explanation: On increasing load, the material passes the elastic range. Now it deforms plastically. Just after elastic range, yielding is encountered.
11. Necking takes place after strain hardening.
a) True
b) False
View Answer
Explanation: Elastic yielding, strain hardening and necking is the right order of regions during ductile fracture. These all are shown on the stress-strain curve.
12. Necking is a result of tri-axial tension.
a) True
b) False
View Answer
Explanation: Necking is a result of uniaxial tension. Tri-axial tension causes the material to fail in a brittle manner.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
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