# Youngs Modulus and its Units | Proportional Limit | Ultimate Stress | Rupture Stress

Sunday, December 5, 2010 8:18**Modulus of Elasticity:**** **

In solid mechanics, Young’s modulus (E) is a measure of the stiffness of a material.It is defined as the ratio of stress over strain in the region in which Hooke’s Law is obeyed for the material.

**Units**

Young’s modulus is the ratio of stress, which has units of pressure to strain, which is dimensionless; therefore Young’s modulus itself has units of pressure.

**Proportional Limit :**

The point up to which the stress and strain are linearly related is called the proportional limit.

**Ultimate Stress :**

The largest stress in the stress strain curve is called the ultimate stress.

**Rupture Stress :**

The stress at the point of rupture is called the fracture or rupture stress.