## Stress

When a material is subjected to an external force, a resisting force induced. The internal resistance force per unit area is called stress.
 Stress Formula

Unit:    N/m2

### Type of stress

• Normal Stress
 Normal Stress
 Normal Stress Formula

• Shear Stress
 Shear Stress
 Shear Stress Formula

• Bulk Stress
 Bulk Stress
 Bulk Stress Formula

## Strain

Deformation per unit length in the direction of deformation is known as strain. It is a dimensionless quantity.

 Strain Formula

### Types of Strain

• Normal Strain
 Normal Strain
 Normal Strain Formula

• Shear Strain
 Shear Strain
 Shear Strain Formula

• Bulk Strain
 Bulk Strain
 Bulk Strain Formula

## True Stress and True Strain

True stress is defined as the ratio of load to the instantaneous area.

 True Stress

Where Ïƒ and Îµ are the engineering stress and engineering strain respectively.

The true strain is defined as

 True Strain

## Stress-Strain Curve

 Stress-Strain Curve

NOTE:

• Limit of Proportionality: It is the stress at which the stress-strain curve is a straight line(OA).
• Hook's law is valid up to the proportionality limit.
• Elastic limit: point in the stress-strain curve up to which the material remains elastic. There is no permanent deformation up to this point.
• Plastic Range: Region between elastic limit and point of fracture.
• Yield Point: The point just beyond the elastic limit, at which material goes increase in length without further increase in the load.