1. If the load being applied is 2000kg, and the area of impression is 250 Square millimetres, what is the Brinell number of the test material?
a) 80 kg per square millimeter
b) 25 kg per square millimeter
c) 20 kg per square millimeter
d) 8 kg per square millimeter
Explanation: Brinell hardness number = \(\frac{Load \,Applied}{Area \,of \,impression \,(spherical)}\)
= \(\frac{2000}{250}\)
= 8 kg per square millimeter.
2. Which of the following is not a way to prepare the test material for the Brinell hardness test?
a) Grinding
b) Layering
c) Filing
d) Polishing
Explanation: The requirements of the specimen for Brinell testing method is similar to the remaining test methods. There are several ways to prepare the material for the test. Grinding, filing and polishing using emery paper are done. Layering is not one of the methods.
3. To perform Brinell test on a soft material like bronze _____________ kg of load is applied on the specimen.
a) 3000
b) 500
c) 6600
d) 1200
Explanation: Different amount of load are applied on test specimen depending upon the type of material being tested. For steel testing, the pressure applied is 3000kg. For comparatively softer materials like aluminium alloys, the pressure applied is 500kg.
4. Rockwell hardness test uses either a ____________ ball or ___________ cone for measuring hardness.
a) steel, diamond
b) diamond, steel
c) carbon, iron
d) iron, carbon
Explanation: Rockwell hardness value is found by calculating the penetration of either a steel ball or diamond cone under a particular load. The Rockwell hardness number appears on the dial of the machine.
5. The Rockwell hardness testing method typically uses certain amounts of load. Which of the following is not one of the loads used?
a) 150kg
b) 60kg
c) 5kg
d) 100kg
Explanation: The loads being applied in the Rockwell hardness method usually on the penetrator(steel ball or diamond cone) being used and the test specimen. The loads applied are typically 100kg, 150kg and 60kg.
6. To find a true hardness reading for hard steel, the minimum thickness required for material is ____
a) 0.0027mm
b) 6.858mm
c) 0.27mm
d) 234mm
Explanation: To obtain the Rockwell hardness value, the loads used or penetrators depends on the weather the material is soft or hard. The minimum thickness required for hard steel is 6.858mm. This will give an accurate hardness value.
7. In the beginning of the Rockwell hardness experiment, the reading dial is set to _____
a) 100
b) 50
c) 0.1
d) 0
Explanation: The dial on the Rockwell hardness test method is where the value can be found. There are two sets of numbers on the dial, black and red. Before the major load is applied on the test specimen, the direct reading dial on the machine has to be fixed to zero.
8. Which of the following hardness testing method is preferred for aircraft manufacturing purposes?.
a) Brinell hardness
b) Rockwell hardness
c) Divider method
d) Shore scleroscope hardness
Explanation: The method of hardness testing usually preferred for aircraft manufacturing purposes is the Rockwell hardness method. This is because it is easy to operate and is reliable. Divider method is used to determine the yield point of a material. It is not a hardness testing method.
9. Which of the following is not a process or property that influences the hardness of a material?
a) Buffing
b) Storing
c) Porous areas
d) Decarburizing
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.
10. What should be done to avoid deflection caused by depression?
a) Plating
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.