**What is stress?**

The internal resistance offered by a body per unit area against deformation is known as stress. The unit of stress is N/mm2

or

N/m2

When an external force acts on a body, the body tends to undergo deformation. Due to cohesion between molecules the body resist the force. This resistance offered by the body is known as strength of material.

Mathematically stress or intensity of stress is written as

σ =P/A

where σ is stress and P is load and A is area of cross section

Note: 1 N/m2 =1 Pascal

1 N/mm2=10 ^6 N/m2

1 bar = 1x105N/m2**What is tensile stress**?

Tensile stress:

The resistance offered by a body per unit area when it is subjected to a force which acts away from its point of application is called tensile stress.

**What is compressive stress**?

Compressive stress:

The resistance offered by a body per unit area when it is subjected to a force which acts towards its point of

application is called compressive stress.**What is shear stress?**

Shear Stress:

The resistance offered by a body per unit area when the applied load on the body consists of two equal and

opposite forces not in the same line is called shear stress.

τ =P/A

where τ is shear stress, P is tangential force and A is area of shearing

**What is strain**?

when a body is subjected to some external force, there is some deformation of the body. The ratio of change of dimension of the body to the original dimension is known as strain. It has no unit.

Strain = change in length ( )/original length ( )

**What is Tensile strain?**

The length of the bar increases by an amount under the action of external force P then tensile strain =increase in length/original length

**What is compressive strain?**

The length of the bar decreases by an amount under the action of external force P then compressive strain =

**What is Shear strain?**

The distortion produced by shear stress on an element or rectangular block is known as shear strain. It can also be defined as the change in the right angle.**What is volumetric strain?**

The ratio between the change in volume and the original volume

is known as volumetric stain.

Volumetric strain =change in volume/original volume

Define True stress and True Strain

The true stress is defined as the ratio of the load to the cross

section area at any instant.