This set of Aerospace Materials and Processes Interview Questions and Answers for freshers focuses on “Aircraft Materials – Hardness testing – Vickers and Shore Scleroscope Hardness”.
1. Which of the following is not a process or property that influences the hardness of a material?
c) Porous areas
Explanation: Due to the properties of the material, the hardness and subsequently tensile strength are affected. Processes like buffing influence the surface of the material. Porous areas and decarburizing also affect the material.
2. What should be done to avoid deflection caused by depression?
b) Unique direction
c) Smooth surface
d) Required edge distance
Explanation: Deflection caused due to depression is one of the possibilities that have to be considered and avoided to obtain the correct result. It can be avoided by ensuring that the experiment is being conducted at the required edge distance.
3. Similar hardness testing machines give the exact same results.
Explanation: The statement is incorrect. Hardness testing machines don not give the exact same results. Even if they are similar in type, obtaining exact same results every time is not possible.
4. The Vickers hardness test consists of a _________ penetrator.
b) steel ball
Explanation: A diamond penetrator is used in a Vickers/diamond pyramid hardness test. The penetrator consists of a pyramid that has a square base. A Steel ball is used in Brinell and Rockwell hardness tests.
5. The penetrator in the Vickers hardness test is a pyramid that is squarely based and has an included angle of _______
Explanation: The included angle of the square based, pyramid diamond penetrator in the Vickers/diamond hardness test is 136°. 15° and 23° would be too low of an angle to be considered.
6. The loading used for a homogenous specimen in the bucket’s hardness test is _______
Explanation: In the Vickers/diamond hardness test, the amount of load applied typically on homogenous material is 30kg. 5kg is the weight applied to materials that are soft or those that have a hard surface.
7. The shore scleroscope hardness test is carried out by ________ a tiny diamond-pointed hammer from a particular altitude and comparing the altitude of rebound to a standard test material.
c) smoothly pressing
Explanation: This hardness test is carried out by comparing the rebound altitude of the test material after dropping a tiny diamond pointed hammer on the test specimen, to that of a standard test material.
8. Which if the following is suggested in the shore scleroscope test to obtain the exact value?
a) Instrument should be in sunlight
b) Instrument should be spray painted
c) Instrument should be fixed rigidly
d) Instrument should be in sleeping position
Explanation: The instrument should be fixed rigidly in a particular position to avoid movement during the experiment. If any movement happens, it might affect the accuracy of the obtained hardness number.
9. In case of shore scleroscope hardness, the number considered is the average of __________ determinations.
Explanation: The shore scleroscope number is obtained by conducting the experiment 5 times and taking an average of the obtained 5 values. The final obtained average value is considered shore scleroscope number.
10. Brinell hardness numbers of materials are identical to ________ hardness numbers.
a) Set method
b) Extension under load
c) Shore scleroscope
Explanation: Brinell hardness numbers are usually similar to Vickers hardness or Diamond pyramid hardness numbers. But hard materials are the only exception to this rule as they are not similar in this case.
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