Normal Stress
Stress
Stress is the expression of force applied to a unit area of surface. It is measured in psi (English unit) or in MPa (SI unit). Another unit of stress which is not commonly used is the dynes (cgs unit). Stress is the ratio of force over area.
$$\text{stress = }\dfrac{\text{force}}{\text{area}}$$
Simple Stresses
There are three types of simple stress namely; normal stress, shearing stress, and bearing stress.
Normal Stress
The resisting area is perpendicular to the applied force, thus normal. There are two types of normal stresses; tensile stress and compressive stress. Tensile stress applied to bar tends the bar to elongate while compressive stress tend to shorten the bar.
$$\sigma = \dfrac{P}{A}$$
where P is the applied normal load in Newton and A is the area in mm2. The maximum stress in tension or compression occurs over a section normal to the load.
