27-07-2012, 09:42 AM
Hardness Test
Hardness Test.pdf (Size: 619.84 KB / Downloads: 378)
Objjectiives
1 This chapter provides fundamental knowledge of
hardness of materials along with different methods of
hardness measurements normally used.
2 Relationships between hardness and tensile properties
will be made and finally factors affecting hardness of
metals will be discussed.
Tapany Udomphol
Introductiion
Definition Hardness is a resistance to deformation.
(for people who are concerned with mechanics of
materials, hardness is more likely to mean the
resistance to indentation)
Hardness tests can be used for many engineering applications to achieve
the basic requirement of mechanical property.
For examples
surface treatments where surface hardness has been much improved.
Powder metallurgy
Fabricated parts: forgings, rolled plates, extrusions, machined parts.
Advantages and disadvantages of
Brinell hardness test
1 Large indentation averages out local
heterogeneities of microstructure.
2 Different loads are used to cover a wide rage of
hardness of commercial metals.
3 Brinell hardness test is less influenced by
surface scratches and roughness than other
hardness tests.
4 The test has limitations on small specimens or
in critically stressed parts where indentation
could be a possible site of failure.
Rockwell hardness test
Principal of the Rockwell Test
1 Position the surface area to be
measured close to the indenter.
2 Applied the minor load and a zero
reference position is established
3 The major load is applied for a specified
time period (dwell time) beyond zero
4 The major load is released leaving the
minor load applied.
The Rockwell number represents
the difference in depth from the zero
reference position as a result of the
applied major load.
Deeper indentation
Softer material
The dial contains 100 divisions,
each division representing a
penetration of 0.002 mm.
Hardness Test.pdf (Size: 619.84 KB / Downloads: 378)
Objjectiives
1 This chapter provides fundamental knowledge of
hardness of materials along with different methods of
hardness measurements normally used.
2 Relationships between hardness and tensile properties
will be made and finally factors affecting hardness of
metals will be discussed.
Tapany Udomphol
Introductiion
Definition Hardness is a resistance to deformation.
(for people who are concerned with mechanics of
materials, hardness is more likely to mean the
resistance to indentation)
Hardness tests can be used for many engineering applications to achieve
the basic requirement of mechanical property.
For examples
surface treatments where surface hardness has been much improved.
Powder metallurgy
Fabricated parts: forgings, rolled plates, extrusions, machined parts.
Advantages and disadvantages of
Brinell hardness test
1 Large indentation averages out local
heterogeneities of microstructure.
2 Different loads are used to cover a wide rage of
hardness of commercial metals.
3 Brinell hardness test is less influenced by
surface scratches and roughness than other
hardness tests.
4 The test has limitations on small specimens or
in critically stressed parts where indentation
could be a possible site of failure.
Rockwell hardness test
Principal of the Rockwell Test
1 Position the surface area to be
measured close to the indenter.
2 Applied the minor load and a zero
reference position is established
3 The major load is applied for a specified
time period (dwell time) beyond zero
4 The major load is released leaving the
minor load applied.
The Rockwell number represents
the difference in depth from the zero
reference position as a result of the
applied major load.
Deeper indentation
Softer material
The dial contains 100 divisions,
each division representing a
penetration of 0.002 mm.