This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Hardness Tests on Metals”.
1. What kind of indenter is used in a Brinell test?
a) Diamond cone
b) Steel ball
c) Pen dot
d) Long tube
Explanation: Brinell Hardness Test is one of the three available tests for checking the hardness of a material. Here, a hardened steel or tungsten carbide ball indenter is forced into the surface of the metal to be tested.
2. For how long is the load maintained in a Brinell test?
a) 2-4 seconds
b) 10-15 seconds
c) 20-30 seconds
d) 45-55 seconds
Explanation: In the Brinell hardness test, the indenter is forced into the surface of the metal and maintained there for 10-15 seconds. This can take a standard load of 500-3000 kg in 500 kg increments.
3. How does the Vicker’s hardness test differ from Brinell’s?
a) Duration of indentation
b) Type of indenter
c) Materials to be tested
d) Load applied
Explanation: Similar to Brinell’s test, Vicker’s test also employs forcing of the indenter into the surface of metal for about 10-15 seconds. However, instead of a ball indenter, a pyramid-shaped indenter is used. This test is commonly also called the diamond-pyramid hardness test.
4. What is the angle of indenter in Vicker’s hardness test?
a) 96 degrees
b) 110 degrees
c) 136 degrees
d) 150 degrees
Explanation: In Vicker’s hardness test, a square pyramid-shaped indenter is used for indentation. This indenter is placed at an angle of 136 degrees between opposite faces. This angle was chosen as it approximates the most desirable ratio of indentation diameter to ball diameter in Brinell hardness test.
5. How is the Vicker’s hardness number defined as?
b) 1.8544P 1/D2
c) 8.544P 1/D2
Explanation: The diamond-pyramid number (DPH) is defined as the applied load divided by the surface area of indentation. Vickers hardness number (VHN or VPN) is also known as diamond-pyramid hardness number. Mathematically, it is defined as 1.8544P 1/D2 . This can be calculated since angle of indenter is known as 136 degrees.
6. The indenter used in C-scale of Rockwell hardness test is named _________
Explanation: There are many scales on which Rockwell hardness tests can be conducted. The B-scale uses a 1/16 inch diameter steel ball indenter. The C-scale uses a diamond cone indenter of 120 degrees, which is named as BRALE.
7. Which of the following is not a Rockwell hardness scale?
Explanation: There are several scales on which Rockwell hardness tests may be conducted. The A-scale uses a diamond cone indenter, whereas E-scale and K-scale use a 1/8 inch diameter steel ball of 100 kg and 150 kg indenting loads respectively.
8. Which materials are to be tested using an F-scale?
a) Copper and brass
b) Case hardened steels
c) Bronze, gunmetal, and beryllium copper
Explanation: The Rockwell hardness F-scale uses a 1/16 inch diameter steel ball indenter with a total indenting load of 60 kg. This is used for testing of copper and brass.
9. Which of the following scales are used for testing of very soft thermoplastics?
Explanation: The A-scale is used for thin hardened steel strips, E-scale is used for cast iron, aluminum alloys, and magnesium alloys, and H-scale is used for soft aluminum and thermoplastics. The R-scale uses a ½ inch diameter steel ball indenter and is used for very soft thermoplastics. For other thermoplastics, the L-scale is used.
10. What is the load that the Vickers hardness test can carry?
a) 10 kg
b) 120 kg
c) 150 kg
d) 3000 kg
Explanation: Brinell’s hardness tests can be used up to 3000 kg for a steel ball. Both B-scale and C-scale of Rockwell have a minor load capacity of 10 kg and a major load capacity of 100 kg and 150 kg respectively. The Vickers test has a load of 1-120 kg and can be used in all metal alloys and ceramics.
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