Stress is a result that is caused when a solid e.g. metal bar is subjected to an external force. Stress is defined as force per unit area and the basic unit includes MN/m2, N/mm2 and Pa. There are basically three types of stress:

► Tensile stress: it is the stress that is setup when the force tries to pull the material apart.

► Compressive stress: it is the stress that is produced by the force that is trying to crush the material.

► Shear stress: is the stress that results from the force that tends to cut through the material i.e. tend to put one material slide over another one.