# Manufacturing Engineering Questions & Answers – Non-Destructive Testing

This set of Manufacturing Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Non-Destructive Testing”.

1. What is first step involved in the process of preparing test sample for microstructural examination?
a) Rough polishing
b) Fine grinding
c) Fine polishing
d) Etching

Explanation: Fine grinding involves the use of abrasive silicon carbide, to get a flat surface, that is nearly free of the disturbed or deformed scratches which were introduced in the previous sample preparation step. For reference, the sample preparation steps are depicted in the below schematic:

2. Which of the following compound is used for fine polishing?
a) Aluminum oxide
b) Nitric oxide
c) Silicon carbide
d) Iron oxide

Explanation: Powder form of aluminum oxide is used for fine polishing process. It is surface treatment process.

3. Etching of specimen is done to achieve ___________
a) Visible grain boundary
b) Invisible grain boundary
c) Toughness
d) Hardness

Explanation: Etching is done to obtain visible grain boundary. It is a surface treatment process.

4. What is the average grain diameter (in mm) for the grain size ASTM grain size 12?
a) .0066
b) .0078
c) .0021
d) .0056

Explanation: According to ASTM standard E1112, ”standard test methods for determining average grain size”:
n = 2G-1, where ‘G’ is the grain size number and ‘n’ represents the average number of grains per square inch at a magnification of 100X. Upon calculations one can deduce that:
Average Grain diameter (d, in mm) = $$\frac{1}{\sqrt{\frac{n×10^4}{645}}}$$
Given ASTM grain size 12, thus, n = 212-1 = 211 = 2048
Therefore, average grain diameter = $$\frac{1}{\sqrt{\frac{2048×10^4}{645}}}$$ = 0.0056 mm.

5. Equipment used for inspection of inside portion of hollow chamber or narrow tube is known as ___________
a) Endoscope
b) Telescope
c) Borescope
d) Flexiscope

Explanation: Borescope is used for visual of inside portion of the hollow chamber.
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6. What is the value of average number of grains in per square inch for ASTM 11?
a) 2048
b) 1024
c) 6
d) 5

Explanation: According to ASTM standard E1112, ”standard test methods for determining average grain size”:
n = 2G-1, where ‘G’ is the grain size number and ‘n’ represents the average number of grains per square inch at a magnification of 100X.
Given ASTM grain size 12, thus, n = 211-1 = 210 = 1024.

7. Which of the following property will be more in fine grained structure?
a) Ductility
b) Corrosion resistance
c) Creep resistance
d) Hardness

Explanation: Finer the grain size (lower the grain size), more is the number of grain boundaries, thus more is the yield strength, thus more is the ductility. This is the reason why we can easily draw a fine-grained structure into wires.

8. Which of the following property will be more in coarse grain structure?
a) Ductility
b) Corrosion resistance
c) Hardness
d) Toughness

Explanation: Grain boundaries are susceptible to corrosion. Coarse grain structure has less grain boundaries, thus has greater corrosion resistance.

9. Which of the following penetrating liquid is used in a liquid penetration test?
a) Water
b) Chlorine based solvent
c) Petroleum based carrier fluid
d) Fluorine based solvent

Explanation: In liquid penetration test, either petroleum-or-water based carrier fluids are used as solvents or cleaners according to the type of penetrant used. Petroleum based carrier fluid is used as penetrating liquid in liquid penetration test along with fluorescent red colour dye for visible light.

10. Which of the following non destructive testing is used to detect change in composition of any material?
a) Liquid penetration test
b) Ultrasonic test
c) Eddy current test

Explanation: Radiography enables us to detect the change in composition. X-rays or γ-rays are used in radiography technique.

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