What is stress ? 

Stress is a term used to describe the internal forces that develop within a material when it is subjected to an external force or load. 

Tensile stress

This type of stress arises when a material is stretched, causing its length to increase.

Compressive stress

This type of stress arises when a material is compressed, causing its length to decrease.

Shear stress

This type of stress arises when a force is applied parallel to a material's surface, causing its particles to slide past each other.

Hydrostatic stress

This type of stress arises when a material is subjected to a uniform pressure from all directions.