Mechanical Behaviour Questions and Answers – Ductility

This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Ductility”.

1. The ability of a material to undergo plastic deformation without fracture when subjected to uniaxial tensile force is ___
a) Ductility
b) Malleability
c) Tensile Strength
d) Yield Strength

Explanation: Ductility is the measure of plastic deformation that material can undergo without fracture. While in malleability, compressive force comes into the picture. Yield strength is the ability of a material to withstand tensile stress without plastic deformation.

2. Which metal has the highest ductility?
a) Silver
b) Gold
c) Platinum
d) Aluminium

Explanation: Platinum has the highest ductility of all metals. Its crystal structure is FCC which provides various slip systems and more plastic deformation. Ag, Au and Al have less ductility than Pt.

3. Ductility of ceramics is ___
a) Less than 1%
b) 2 – 4%
c) 4 – 40%
d) More than 40%

Explanation: Ceramics show very less ductility 1%. Polymers show ductility 2-4%. Metals show high ductility of 4 – 40%.

4. What is the ductility of annealed Cu?
a) 25%
b) 35%
c) 40%
d) 45%

Explanation: Cu has a very good ductility of 45%. Annealed steel has a ductility of 25% and annealed molybdenum has 35%. Al has a ductility of 40%.

5. What is the ductility of commercial pure Titanium?
a) 10%
b) 14%
c) 16%
d) 25%

Explanation: Commercial pure titanium in the annealed state has good ductility as high as 25%. Alloying decreases its ductility by strain effect. The ductilities of titanium alloys are 10%, 14% and 16%.

6. Which factor increases ductility?
a) Cold working
b) Annealing
c) Alloying
d) Inclusions

Explanation: Annealing process reduces stress inside the structure. Thus ductility of material increases. Cold working, alloying and the presence of inclusions reduce the ductility of materials.

7. Which crystal structure materials possess the best ductility properties?
a) FCC
b) HCP
c) BCC
d) SC

Explanation: Crystals of FCC structure have 12 slip systems which are active on room temperature. So these show good ductility properties. Other crystal structures are not much ductile as FCC.

8. Which factor decreases the ductility of materials?
a) Annealing
b) Spheroidization
c) Grain refinement
d) Alloying

Explanation: Pure materials have a higher ductility than their alloys. It is because of the strain hardening effect which is due to atom size difference. Annealing and spheroidization decrease ductility by reducing stress raising regions.

9. Cast materials show better ductility than wrought materials.
a) True
b) False

Explanation: Cast materials generally have lower ductility than wrought materials. Wrought alloys are more uniform than cast alloys. Cast alloys have segregation during solidification which reduces ductility.

10. Neutron irradiation by neutrons can ___ yield stress and ___ ductility.
a) Increase, increase
b) Increase, decrease
c) Decrease, increase
d) Decrease, decrease

Explanation: Neutron irradiation produces defects in the crystal. These defects increase the yield stress of the material. Simultaneously ductility of the material decreases.

11. With the increase in the degree of stress triaxiality, ductility of material decreases.
a) True
b) False

Explanation: Stress triaxiality is the ratio of hydrostatic pressure, to the von mises equivalent stress. Triaxiality factor can be taken σ3/ σ1 where σ1 > σ2 > σ3 as σ3/ σ1 increases the ductility of material decreases.

12. As the strain rate increases, the value of ductility ___
a) Increases
b) Decreases
c) Remains constant
d) Changes independent of strain rate.

Explanation: As the stain rate increases, the material tends to behave as a brittle material. It lowers the value of ductility of the material. By decreasing the rate of deformation, material becomes softer.

13. Original gauge length of aluminium cylindrical spectrum is 2 inches and fracture length is 2.78 inches. What is the ductility of specimen?
a) 38%
b) 39%
c) 40%
d) 41%

Explanation:
Here, lf = Fracture length, l0 = original length.

14. A cylindrical specimen having diameter of 12.8 mm is starting and 7.3 mm at the fracture point. What is ductility?
a) 56%
b) 64%
c) 67%
d) 78%

Explanation: Ductility = $$\frac{(A_0 – A_f)}{A_0}$$ × 100
Here, A0 = original cross-sectional area of specimen, Af = original cross-sectional area at fracture point.
= $$\frac{(\pi(6.4)^2 – \pi(3.65)^2)}{\pi(6.4)^2}$$ × 100
= $$\frac{(128.68 – 41.853)}{128.68}$$ × 100
= 0.675 × 100 = 67.5%.

Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.

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