Question 1
For hard materials, the indenter of the Brinell hardness tester is made of __________
A. steel
B. diamond
C. tungsten carbide
D. copper
View Answer
Answer: Option C
Explanation:
For the hard material, to avoid the distortion of the ball, the tungsten carbide ball is used as the indenter. Generally, the steel ball is used for the measurement.
Question 2
Hardness of most metals fall in the range of __________ in Mohr’s scale.
A. 1-3
B. 3-6
C. 4-8
D. 7-10
View Answer
Answer: Option C
Explanation:
Hardness of most metals fall in the range of 4-8 in Mohr’s scale. But the disadvantage of using this scale is that the range is widely spaced for metals.
Question 3
How is Brinell hardness measured?
A. Using a dial gauge showing hardness reading
B. The graph obtained from machine showing hardness
C. Using an indentation profile which will be checked in a microscope for indentation diameter
D. By checking the deformation of the ball
View Answer
Answer: Option C
Explanation:
The Brinell hardness measurement is done by checking the diameter of indentation in a low magnification microscope. This is divide by the load applied to get the hardness number.
Question 4
In microhardness test, Vickers test uses load less than 1 kgf.
A. True
B. False
View Answer
Answer: Option A
Explanation:
Vickers hardness test may be macro or microhardness test. In case of microhardness test, load is small. It is taken less than 1 kgf.
Question 5
Microhardness test gives average hardness.
A. True
B. False
View Answer
Answer: Option B
Explanation:
Macrohardness tests give average hardness. Microhardness test gives hardness of individual grains or phase.
Question 6
The Brinell Hardness measurement is a concept based on __________
A. indentation
B. shearing
C. rebound
D. scratch
View Answer
Answer: Option A
Explanation:
The Brinell hardness test is the first standardized and widely used method for hardness testing. The principle is based on the indentation of the metal surface with a hardened steel ball.
Question 7
The diameter of the steel ball used in Brinell hardness is ________
A. 10 mm
B. 10 cm
C. 1 mm
D. 3.6 mm
View Answer
Answer: Option A
Explanation:
The diameter of the stell ball used for indentation measurement is 10 mm with a load of 3000 kg. For soft material, it will be reduced to 500 kg.
Question 8
The scratch hardness range is ______________
A. 1-10
B. 1-100
C. 10-1000
D. 100-110
View Answer
Answer: Option A
Explanation:
The scratch hardness is used by mineralogist. It is the ability of one mineral to scratch another. The talc is softest mineral kept at 1 and diamond being hardest is kept at number 10.
Question 9
The Shore hardness test measurement uses the concept of _____________
A. indentation
B. deformation
C. rebound
D. scratch
View Answer
Answer: Option C
Explanation:
The Shore hardness tester uses the concept of rebound indentation from the surface of the sample. The impact of energy is used to calculate the hardness of the material.
Question 10
The stress concentration and notch sensitivity are the same phenomena in the material.
A. True
B. False
View Answer
Answer: Option B
Explanation:
The stress concentration is phenomena associated with increase in stress value in the local area due to any factor. But the notch sensitivity leads explicitly with a local area of triaxle state of stress, which fails due to high-stress condition.
Question 11
The unit of Brinell hardness number is ____________
A. kg
B. kg/mm2
C. kg-mm
D. unitless
View Answer
Question 12
What is Knoop hardness of diamond?
A. 100 HK
B. 1000 HK
C. 7000 HK
D. 9000 HK
View Answer
Answer: Option C
Explanation:
Knoop hardness of diamond is 7000 HK. Brittle materials are tested by Knoop test. Vickers hardness of diamond is 10,000 HV.
Question 13
What is Knoop hardness of gold foil?
A. 68 HK
B. 69 HK
C. 343 HK
D. 820 HK
View Answer
Answer: Option B
Explanation:
Gold foil has a hardness of 69 HK. Dentin has a hardness of 68 HK. Quartz has hardness 820 HK.
Question 14
What is test load used in Micro hardness test?
A. 2-200 gmf
B. 5-1000 gmf
C. 60 gmf
D. 100 gmf
View Answer
Answer: Option B
Explanation:
In the case of micro hardness test, very small load is applied. Its range is 5 to 1000 gmf.
Question 15
What is the disadvantage of the Knoop hardness test?
A. Elastic recovery
B. Soft indenter
C. High load required
D. Cannot use thin specimen
View Answer
Answer: Option A
Explanation:
Knoop hardness test uses diamond indenter. Small load is used. This test gives a higher value of microhardness because of elastic recovery.
Question 16
What is the formula for Knoop hardness number?
A. KHN = h – 500t
B. KHN = 1.854P/L2
C. KHN = P/ D2
D. KHN = P/L2C
View Answer
Answer: Option D
Explanation:
Knoop hardness number is given by formula KHN = P/L2C. Here L is longer diagonal length, P is load and C is constant.
Question 17
What is the shape of indentation by knoop indenter?
A. Semi spherical
B. Square
C. Cone
D. Rhombohedral
View Answer
Answer: Option D
Explanation:
Knoop indenter is a diamond pyramid. It has one of the diagonals longer than the other. Shape of indentation is rhombohedral.
Question 18
Which of the following hardness is least affected by surface scratched and local inhomogeneity of the material?
A. Brinell hardness
B. Mayer hardness
C. Rockwell hardness
D. Vickers hardness
View Answer
Answer: Option A
Explanation:
The diameter of the indenter used is maximum in Brinell hardness measurement, so the indentation is made over the large surface area to take care of local fluctuation.
Question 19
Which of the following is a Microhardness test?
A. Brinell
B. Knoop
C. Rockwell
D. Shore
View Answer
Answer: Option B
Explanation:
Brinell is a Macrohardness test. Knoop indenter is used in Micro hardness testing. Shore hardness is a dynamic hardness test.
Question 20
Which of the following is not a measurement method for hardness?
A. Scratch hardness
B. Indentation hardness
C. Rebound hardness
D. Elongation hardness
View Answer
Answer: Option D
Explanation:
The scratch hardness is commonly used for minerals, indentation and rebound hardness for metals. But there is no such thing as elongation hardness measurement.
Question 21
Which of the following is an angle between opposite faces in Knoop indenter?
A. 130°
B. 120°
C. 136°
D. 122°
View Answer
Answer: Option A
Explanation:
Knoop indenter is a diamond pyramid. The ratio of diagonals is 7:1. The angles between them are 130° and 172°.
Question 22
Which test is more preferred for testing hardness of electroplated surface?
A. Dynamic hardness test
B. Scratch hardness test
C. Macrohardness test
D. Microhardness test
View Answer
Answer: Option D
Explanation:
Hardness of electroplated surface is tested by microhardness test. It may be chrome plating.