# Elastic Behaviour of Materials, Stress and Strain

• Elasticity deals with property of materials, its strength and ability to withstand against external forces which are acting on it.
• The forces acting between the atoms due to Electrostatic interaction between the charges of the atoms are called interatomic forces.
• Attractive forces between the nucleus of one atom and electrons of the other atom. These attractive forces tend to decrease the potential energy of the pair of atoms.
• The force between molecules dues to Electrostatic interaction between the charges of the molecules are called inter molecular forces.
• A body whose size and shape cannot be changed however large the applied forces may be is called rigid body
• The External force which changes or ties to change the shape and size is called a deforming force.
• The internal force which restores the size and shape of the body when deforming force is with drawn is called restoring force.
• The magnitude of deforming force is equal to the Restoring force.
• In a solid each atom or molecules are bonded together by inter atomic forces and in state position.
• Elasticity is the property of a material by virtue of which it regains its original size and shape when deforming forces are withdrawn.
• There is no perfect Elastic material exist in nature Quarts is nearly perfect Elastic body.
• Plasticity is the property of material by virtue if which it does not regain the size and shape when deforming force is removed.
• Steel is more Elastic than rubber.
• The restoring force per unit area is called stress S = F/A
• The stress Normal to the surface called Normal stress and tangential called tangential stress.
• Shearing stress is defined as the Tangential restoring force per unit area of cross section.
• Longitudinal stress and bulk stress are normal stress is which produce change in size, shearing stress is a tangential stress which produce change in shape.
• Bulk stress is defined as the volume restoring force per unit area of cross section.
• Strain is defined as the change in dimension per unit original dimension.
• Linear strain is defined as the change in length to unit original length.
• Shear strain is defined as the linear displacement of layer to distance between layers
• Bulk strain is defined as the change in volume per unit original volume.

### View the Topic in this video From 0:47 To 56:34

Disclaimer: Compete.etutor.co may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. Compete.etutor.co makes no representations whatsoever concerning the content of these sites and the fact that compete.etutor.co has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by compete.etutor.co with respect to such sites, its services, the products displayed, its owners, or its providers.

1. Stress: The internal restoring force acting per unit area of a deformed body is called stress.
\tt Stress = \frac{Restoring\ force}{Area}=\frac{F}{A}

2. Strain
The fractional change in configuration is called strain.
\tt Strain = \frac{Change\ in\ configuration}{Original\ configuration}

3. Longitudinal strain = \tt \frac{Change\ in\ length}{Original\ length}=\frac{\Delta l}{l}

4. Volumetric strain = \tt \frac{Change\ in\ volume}{Original\ volume}=\frac{\Delta v}{v}

5. Shearing strain = Angular displacement of the plane perpendicular to the fixed surface. \tt \phi=\frac{x}{L}