Elasticity
It is the property under which a material deformed under the load is enabled to return to its original dimension when the load is removed.
- If the body regains completely its original shape it is called a perfectly elastic body.
- Elastic limit marks the partial breakdown of elasticity beyond which removal of load results in a degree of permanent deformation.
- Steel, aluminum, copper, concrete may be considered to be perfectly elastic within a certain limit.
Plasticity
The characteristics of the material by which it undergoes inelastic strain beyond those at the elastic limit are known as plasticity.
- This property is particularly useful in the operation of pressing and forging.
- When large deformation occurs in a ductile material loaded in the plastic region, the material is said to undergo plastic flow.
Ductility
It is the property that permits a material to be drawn out longitudinally to a reduced section, under the action of tensile force.
- A ductile material must possess a high degree of plasticity and strength.
- Ductile material must have a low degree of elasticity.
- This is useful in wire drawing
Brittleness
It is a lack of ductility. Brittleness implies that it cannot be drawn out by tension to a smaller section
- In brittle material, failure take place under load without significant deformation
- Ordinary Glass is a nearly ideal brittle material.
- Cast iron, concrete, and ceramic material are brittle materials.
Malleability
It is the property of a material that permits the material to be extended in all directions without rupture.
- A malleable material possesses a high degree of plasticity, but not necessarily great strength.
Toughness
It is the property of the material that enables it to absorb energy without fracture.
- It is desirable in the material which is subject to cyclic or shock loading.
- It is represented by the area under the stress-strain curve for material up to fracture.
- Bend test used for common comparative test for toughness.
Hardness
A material can resist indentation or surface abrasion.
- Brinell hardness test is used to check the hardness
- Brinell hardness number
Here, P = Standard load
D = Diameter of steel ball (mm)
D = diameter of indent (mm)
Strength
This property enables the material to resist fracture under load
- This is the most important property from the design point of view.
- Load at ultimate point divided by area of a test specimen is termed as ultimate strength.
Strain Energy
Material can absorb energy when it is strained
= P × δ = T × θ
Where, P = Applied load; δ = Elongation due to applied load
T = Applied torque; θ = Angle of twist due to applied torque
Resilience
The ability of a material to absorb energy in the elastic region when it is strained.
The area under P-δ curve = P × δ
Proof Resilience
The maximum energy absorbing capacity of a material in the elastic region is called proof resilience.
The area under P – δ curve = ×
Where, = Load at the elastic limit;
= Elongation up to an elastic limit
Modulus of resilience =
Where = Strain at the elastic limit; E = Modulus of elasticity
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