Describe the various mechanical properties of materials in short. Or Write about the various mechanical properties of metals.

Describe the various mechanical properties of materials in short. Or Write about the various mechanical properties of metals.

Ans. The material properties which are associated with the ability of the

material to resist mechanical forces and loads are known as mechanical

properties. The mechanical properties are a measure of the strength and lasting

characteristics of a material in service. Some important mechanical properties

are described below –

(i) Strength- The resistance offered by a material on application

of external force or load is known as strength. Depending on the type of load

applied, the strength could be compressive, tensile or shear.

Due to load, the material is elastically deformed, which is known as strain.

Mathematically,

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The resistance offered by the material is also known as stress. Stress can

be defined as

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The tensile strength of a material is measured by a tensile test carried out

on a universal testing machine.

(ii) Elasticity- Elasticity of a material is its power of coming back

To its original position after deformation when the stress or load is removed.

In other words, elasticity is that property of a material by virtue of which

deformation caused by applied load disappears upon removal of the load.

Elasticity is a tensile property of the material.

 

(iii) Plasticity – The plasticity of a material is its ability to undergo

some degree of permanent deformation without rupture or failure. The plastic

deformation takes place beyond the elastic limit. This property of a material is

important in forming, extruding, shaping and many other cold or hot working

processes. Generally, plasticity decreases with decreasing temperature. Material

such as steel is plastic at bright heat and lead, clay etc., are plastic at room

temperature.

(iv) Stiffness-Stiffness is defined as the resistance of a material to

elastic deformation or deflection. It is also called rigidity. A material which

suffers more deformation under load has a low degree of stiffness or rigidity.

For example, suspended beams of aluminium and steel may both sufficiently

strong to carry the required load but the aluminium beam will bend or deflect

further. In other words, the aluminium beam is less stiffer than steel beam. If

the material follows Hook’s law, its stiffness or rigidity is measured by the

Young’s modulus E. The higher the value of Young’s modulus, the stiffer the

material.

In compressive and tensile stress, it is known as modulus of elasticity or

modulus of stiffness; in volumetric distortion, it is called the bulk modulus.

The term flexibility is sometimes used as the opposite of stiffness.

(v) Ductility – It is the property of a material which enables it to

draw into the shape of wire. Mild steel is an example of ductile material. The

percentage elongation and the reduction in area in tension is often used as

empirical measure of ductility.

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A material is generally said to be ductile if the percentage elongation is

more than 5 in a gauge length of 50 mm. Mild steel, copper, aluminium, zinc,

nickel, tin etc., are ductile metals.

(vi) Malleability – This is the property by vil1ue of which a material

may be hammered or rolled into thin sheets without rupture. This property

increases with increase of temperature. Aluminium, copper, tin, lead, steel

etc., are malleable metals.

(vii) Toughness (or Tenacity) – Toughness is the strength with which

the material opposes rupture. It is a measure of the amount of energy, a material

can absorb before actual fracture or failure takes place. Mild steel is tougher

than glass.

(viii) Brittleness– Brittleness of a material is the property of breaking

without much permanent distortion. In other words, lack of ductility is

brittleness. If a body breaks easily when subjected to shocks it is said to be

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