## 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 σ and ε 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.