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Mechanical Properties of Metals
The mechanical properties of the metals are those which are associated with the ability of the material to resist mechanical forces and load.
Often materials are subject to forces (loads) when they are used. Mechanical engineers calculate those forces and material scientists how materials deform (elongate, compress, twist) or break as a function of applied load, time, temperature, and other conditions.
Materials scientists learn about these mechanical properties by testing materials. Results from the tests depend on the size and shape of material to be tested (specimen), how it is held, and the way of performing the test. That is why we use common procedures, or standards.
1. Strength:
3. Elasticity:
It is the ability of a material to resist the externally applied forces
without breaking or yielding.
The internal resistance offered by a part to an externally applied force is
called stress.
2. Stiffness:
without breaking or yielding.
The internal resistance offered by a part to an externally applied force is
called stress.
2. Stiffness:
It is the ability of a material to resist deformation under stress.
The modulus of elasticity is the measure of stiffness.
The modulus of elasticity is the measure of stiffness.
3. Elasticity:
It is the property of a material to regain its original shape after
deformation when the external forces are removed.
This property is desirable for materials used in tools and machines.
It may be noted that steel is more elastic than rubber.
4. Plasticity:
deformation when the external forces are removed.
This property is desirable for materials used in tools and machines.
It may be noted that steel is more elastic than rubber.
4. Plasticity:
It is property of a material which retains the deformation produced under load permanently.
This property of the material is necessary for forgings, in stamping images on
coins and in ornamental work.
5. Ductility:
This property of the material is necessary for forgings, in stamping images on
coins and in ornamental work.
5. Ductility:
It is the property of a material enabling it to be drawn into wire with
the application of a tensile force.
The ductility is usually measured by the terms, percentage elongation and
percentage reduction in area.
The ductile material commonly used in engineering practice (in order of
diminishing ductility) are mild steel, copper, aluminium, nickel, zinc, tin and
lead.
6. Malleability:
the application of a tensile force.
The ductility is usually measured by the terms, percentage elongation and
percentage reduction in area.
The ductile material commonly used in engineering practice (in order of
diminishing ductility) are mild steel, copper, aluminium, nickel, zinc, tin and
lead.
6. Malleability:
It is a special case of ductility which permits materials to be rolled or
hammered into thin sheets.
The malleable materials commonly used in engineering practice (in order of
diminishing malleability) are lead, soft steel, wrought iron, copper and
aluminium.
7. Brittleness:
hammered into thin sheets.
The malleable materials commonly used in engineering practice (in order of
diminishing malleability) are lead, soft steel, wrought iron, copper and
aluminium.
7. Brittleness:
It is the property of a material opposite to ductility. It is the property
of breaking of a material with little permanent distortion.
Brittle materials when subjected to tensile loads, it snaps off without giving
any sensible elongation.
For example, cast iron is a brittle material.
8. Toughness:
of breaking of a material with little permanent distortion.
Brittle materials when subjected to tensile loads, it snaps off without giving
any sensible elongation.
For example, cast iron is a brittle material.
8. Toughness:
It is the property of a material to resist fracture due to high impact loads like hammer blows.
The toughness of the material decreases when it is heated.
It is measured by the amount of energy that a unit volume of the material has
absorbed after being stressed upto the point of fracture.
This property is desirable in parts subjected to shock and impact loads.
9. Machinability:
The toughness of the material decreases when it is heated.
It is measured by the amount of energy that a unit volume of the material has
absorbed after being stressed upto the point of fracture.
This property is desirable in parts subjected to shock and impact loads.
9. Machinability:
It is the property of a material which refers to a relative case with which a material can be cut.
10. Resilience:
10. Resilience:
It is the property of a material to absorb energy and to resist shock and impact loads.
It is measured by the amount of energy absorbed per unit volume within elastic limit.
This property is essential for spring materials.
11. Creep:
It is measured by the amount of energy absorbed per unit volume within elastic limit.
This property is essential for spring materials.
11. Creep:
When a part is subjected to a constant stress at high temperature for a long period of time, it will undergo a slow and permanent deformation called creep.
This property is considered in designing internal combustion engines, boilers
and turbines.
12. Fatigue:
This property is considered in designing internal combustion engines, boilers
and turbines.
12. Fatigue:
When a material is subjected to repeated stresses, it fails at stresses below the yield point stresses. Such type of failure of a material is known as fatigue.
The failure is caused by means of a progressive crack formation which are usually fine and of microscopic size.
This property is considered in designing shafts, connecting rods, springs, gears, etc.
13. Hardness:
The failure is caused by means of a progressive crack formation which are usually fine and of microscopic size.
This property is considered in designing shafts, connecting rods, springs, gears, etc.
13. Hardness:
It is a very important property of the metals and has a wide variety of meanings.
It embraces many different properties such as resistance to wear, scratching,
deformation and machinability etc.
It also means the ability of a metal to cut another metal.
The hardness is usually expressed in numbers which are dependent on the
method of making the test.
The hardness of a metal may be determined by the following tests:
(a) Brinell hardness test, (b) Rockwell hardness test,
(c) Vickers hardness test and (d) Shore scleroscope.
It embraces many different properties such as resistance to wear, scratching,
deformation and machinability etc.
It also means the ability of a metal to cut another metal.
The hardness is usually expressed in numbers which are dependent on the
method of making the test.
The hardness of a metal may be determined by the following tests:
(a) Brinell hardness test, (b) Rockwell hardness test,
(c) Vickers hardness test and (d) Shore scleroscope.
References : Introduction to machine design, SUNIL G. JANIYANI, Darshan Institute of Engineering & Technology, Rajkot
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