Materials


Stress and strain

When talking about materials, the two terms above are often used. Stress refers to the amount of force that is being exerted over a particular area. The term breaking stress (often referred to as strength) refers to the amount of stress a material can be subjected to before undergoing a deformation of some kind. 

Stress = Force/Area

Strain, on the other hand, refers to the amount of deformation an object experiences - it is equal to the change in dimension of a deformed object, divided by the dimension of the object before it underwent deformation. Therefore, breaking strain refers to the amount of strain an object can undergo before breaking in some way. 

Strain = Extension/Original length (NO UNITS)

Young's modulus

Young's modulus refers to the amount of stress needed to change a materials shape by a certain amount. It is often written as:

Young modulus = stress/strain (Pa)