What is the definition of hardness?
Material hardness is the ability of a material to withstand force without deformation, scratching, penetration, and indentation.
What are the three types of hardness?
scratch hardness
rebound hardness
Insentation hardness
What scale is used to determine the scratch hardness?
Mohs scale
How are Mohs hardness tests conducted?
Scratching materials against eachother in increasing hardness. 10 Stages with the highest being diamond.
What is rebound hardness?
The elastic hardness, which lets the body regain its shape after the force is removed.
How is rebound hardness measured?
By dropping a diamond coated hammer on the material and observing the rebound height.
What are the indentation hardness maethods?
Brinell hardness
Rockwell hardness
Vickers Hardness
Knoop hardness
How is the Brinell hardness calculated?
two diameters for accuracy
What is the diameter and the material of the brinell indenter?
10mm diameter steel ball
What is the relation between tensile strength and brinell hardness?
What are the loads for which approximate brinell hardness?
How long should the load be applied for brinell hardness?
15s-30s
What does HBW 10/3000 mean?
The brinell hardness measuring process was used with a tungsten carbide ball of 10mm and a force of 3000 kg*g
What is the brinell hardness range of steel?
120-900 HB
What is the penetrator in the rockwell hardness test?
Either a steel ball or a diamond cone
How is the Rockwell hardness determined?
What is the typical value hardness value of a hard steel in the Rockwell scale?
55-65 HRC
How is the load in the VIckers hardness test calculated?
What is the minimum distance between vickers indentations?
2,5 d for steels and harder
3 d for softer materials
How is the Knoop hardness determined?
For which materials is the Knoop hardness test best applied?
Ceramics
For what materials is the Brinell test best not used?
Non ductile materials
For which materials is the shore hardness test applied?
elastomers
thermoplastic polymers
What is measured in the shore hardness method?
The displacement of the tip
What identation geometry is used for nano indentation?
Three sided pyramid. (Berkovich tip)
Which methods are used to image the identations of nanoindentation?
Atomic force microscopy
scanning electron microscopy
How is the area of indentation calculated in nanoindentation?
By using the depth and the known geometry of the indenter
How can the reduced modulus be calculated in Nanoindentation?
S=stiffness of contact
beta=geometrical constant
A=projected area (often approximated by:
)
How can the youngs modulus be calculated in Nanoindentation?
vi=poisson of indenter
Ei=youngs modulus indenter
subscript s for material
How is the hardness obtained in Nano indentation?
Which properties can be obtained form nano indentation?
elastic modulus
hardness
fracture toughness
creep
dynamic properties
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