Chapter 1, lesson 2 Flashcards
(16 cards)
What are the 3 hardness test?
- Brinell
- Vickers
- Rockwell
What are the conditions for a Brinell hardness specimen test to be successful?
- The thickness of the specimen must be sufficient enough
- The ratio of Force/Distance ² must be correct
Why must the specimen be thick enough?
- Allow unrestricted deformation to perform below the impression
- To eliminate the test supporting block especially in softer materials as more deformation may happen
Why must the ratio of Force against distance squared be correct?
- if load is too high, the indenter ball can deform especially on very hard material
- If load is too low, the indentation produced will be shallow and small
What’s the advantages and disadvantages of the Brinell hardness test?
Adv: shows closer relations to the tensile strength
Did: cannot be used for very hard materials
What’s special about Vickers hardness test?
• It helps to overcome the disadvantages of Brinell test as the diamond indentor is the hardest material
How do we measure HV?
- Measure the 2 diagonals distances of the impression made
- HV is related to the diagonal distance and load
- HV= 1.854 F/d^2
What are the advantages and disadvantages of the Vickers Hardness test?
Adv:
• Accuracy don’t vary, it is suitable for precision test
• Limited product surface damage
Dis:
•More expensive
•More surface preparation work
How does the Rockwell hardness test work?
• It’s determined by depth penetration or the impression
• 2 Load is needed for this test: Major load, Minor load
Whats the difference between the ROCKWELL A, B AND C?
A: uses a major load of 100 kgf using a 1.6 mm steel ball on copper alloys or normalized steel
B: uses a major load of 150 kgf using a 120°C apex angle diamond on hard materials
C: uses a major load of 60 kgf using a 120°C apex angle diamond on hard and thin materials
What are the advantages and disadvantages of the Rockwell test
Adv:
• very rapid and quick
• wide range of scales
Dis:
• too many scales
• cannot be used for thin materials• Not reliable as Vickers hardness value
What is the impact test for?
It is to test the behaviour of a material under sudden impact loaded as to indicate the toughness, brittleness
What are the two types of impact test?
- Charpy: where two ends are supported and the sticker hits at the centre
- Izod where it is held at one end and the sticker hits at the other end
Explanation of the impact test?
The big pendulum will swing from the right side to the left side and back. The more brittle a material is the lesser energy is required which means the toughness is lower.
What’s the traits of a brittle material during the impact test?
- The sample is not smooth
- The pitch is higher but softer
What is the definition of hardness?
Hardness is the ability of a material to resist deformation
