MATERIAL PROPERTIES AND BEHAVIOUR

Physical properties
=Can be observed or measured without changing the composition of matter. Physical properties are used to observe and describe matter.

Thermal properties =Thermal properties explain the response of a material to the application of heat eg: •Heat capacity
•Thermal expansion •Thermal conductivity
-Thermal stresses

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• Heat capacity:

-- energy required to increase a mole of material by a unit T -- energy is stored as atomic vibrations

• Coefficient of thermal expansion:

-- the size of a material changes with a change in temperature -- polymers have the largest values

• Thermal conductivity:

-- the ability of a material to transport heat

-- metals have the largest values

• Thermal shock resistance:

-- the ability of a material to be rapidly cooled and not fracture

Thermal conductivity Thermal expansion Electrical conductivity Magnetic properties Corrosion Density Melting Point

Heat Capacity-The ability of a material to absorb heat
Thermal Conductivity-The ability of a material to transport heat

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Electrical Properties

Electrical conductivity Electrical resistance

STRENGTH: The ability of a material to stand up to forces being applied without it bending, breaking, shattering or deforming in any way.

TOUGHNESS: ability of a material's resistance to fracture. It is often expressed in terms of the amount of energy a material can absorb before fracture.

BRITTLENESS: disability of a material to undergo plastic deformation.

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HARDNESS The ability of a material to resist scratching, wear and tear and indentation.                                                                  
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5.ELASTICITY
The ability of a material to absorb force and flex in different directions, returning to its original position
6.PLASTICITY
The ability of a material to be change in shape permanently.
7.DUCTILITY The ability of a material to change shape (deform)

Mechanical Properties

Fatigue behavior:
Fatigue = failure under cyclic stress

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Fatigue is the lowering of strength or failure of a material due to repetitive stress, which may be above or below the yield strength.

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Cracks generally grow under repeated loading

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Trucks passing over bridges,
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Bicycle pedals
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gear
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• Creep is the tendency of a solid material to slowly deform permanently under the influence of stresses.
• Creep occurs when a metal is subjected to a constant tensile load at an elevated temperature.
• Creep is found to occur at higher temperature than at lower temperature.
• Therefore the study of creep is very important for those materials which are used at high temperature like components of gas turbines, furnaces, rockets, missiles etc.

Fracture mechanisms

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• Ductile fracture

• Occurs with plastic deformation

• Brittle fracture

– Occurs with Little or no plastic deformation

– rapid run of cracks through a stressed material